Arvicanthis

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Laura Smale - One of the best experts on this subject based on the ideXlab platform.

  • acute behavioral responses to light and darkness in nocturnal mus musculus and diurnal Arvicanthis niloticus
    Journal of Biological Rhythms, 2012
    Co-Authors: Dorela D Shuboni, Antonio A. Nunez, Lily Yan, S Cramm, Laura Smale
    Abstract:

    The term masking refers to immediate responses to stimuli that override the influence of the circadian timekeeping system on behavior and physiology. Masking by light and darkness plays an important role in shaping an organism's daily pattern of activity. Nocturnal animals generally become more active in response to darkness (positive masking) and less active in response to light (negative masking), and diurnal animals generally have opposite patterns of response. These responses can vary as a function of light intensity as well as time of day. Few studies have directly compared masking in diurnal and nocturnal species, and none have compared rhythms in masking behavior of diurnal and nocturnal species. Here, we assessed masking in nocturnal mice (Mus musculus) and diurnal grass rats (Arvicanthis niloticus). In the first experiment, animals were housed in a 12:12 light-dark (LD) cycle, with dark or light pulses presented at 6 Zeitgeber times (ZTs; with ZT0 = lights on). Light pulses during the dark phase produced negative masking in nocturnal mice but only at ZT14, whereas light pulses resulted in positive masking in diurnal grass rats across the dark phase. In both species, dark pulses had no effect on behavior. In the 2nd experiment, animals were kept in constant darkness or constant light and were presented with light or dark pulses, respectively, at 6 circadian times (CTs). CT0 corresponded to ZT0 of the preceding LD cycle. Rhythms in masking responses to light differed between species; responses were evident at all CTs in grass rats but only at CT14 in mice. Responses to darkness were observed only in mice, in which there was a significant increase in activity at CT 22. In the 3rd experiment, animals were kept on a 3.5:3.5-h LD cycle. Surprisingly, masking was evident only in grass rats. In mice, levels of activity during the light and dark phases of the 7-h cycle did not differ, even though the same animals had responded to discrete photic stimuli in the first 2 experiments. The results of the 3 experiments are discussed in terms of their methodological implications and for the insight they offer into the mechanisms and evolution of diurnality.

  • retinal anatomy and visual performance in a diurnal cone rich laboratory rodent the nile grass rat Arvicanthis niloticus
    The Journal of Comparative Neurology, 2008
    Co-Authors: Frederic Gaillard, Laura Smale, Gregory S Gilmour, Sharee Kuny, Silvina C Mema, Stephan Bonfield, William K Stell, Brent T Martin, Nathan A Crowder, Yves Sauve
    Abstract:

    Unlike laboratory rats and mice, muridae of the Arvicanthis family (A. ansorgei and A. niloticus) are adapted to functioning best in daylight. To date, they have been used as experimental models mainly in studies of circadian rhythms. However, recent work aimed at optimizing photoreceptor-directed gene delivery vectors (Khani et al. [2007] Invest Ophthalmol Vis Sci 48:3954-3961) suggests their potential usefulness for studying retinal pathologies and therapies. In the present study we analyzed the retinal anatomy and visual performance of the Nile grass rat (A. niloticus) using immunohistofluorescence and the optokinetic response (OKR). We found that approximately 35-40% of photoreceptors are cones; that many neural features of the inner retina are similar to those in other diurnal mammals; and that spatial acuity, measured by the OKR, is more than two times that of the usual laboratory rodents. These observations are consistent with the known diurnal habits of this animal, and further support its pertinence as a complementary model for studies of structure, function, and pathology in cone-rich mammalian retinae.

  • a daily rhythm in mating behavior in a diurnal murid rodent Arvicanthis niloticus
    Hormones and Behavior, 2005
    Co-Authors: Megan M Mahoney, Laura Smale
    Abstract:

    The time of day at which mating occurs is dramatically different in diurnal compared to nocturnal rodents. We used a diurnal murid rodent, Arvicanthis niloticus, to determine if inverted rhythms in responsiveness to hormones contribute to this difference. Male and hormone-primed female grass rats were tested for mating behavior at four different times of day (ZT 5, 11, 17, 23; ZT 0=lights-on). In females, there was considerable inter-individual variability with respect to patterns of responsiveness to hormones. Overall, the lordosis quotient (LQ) was rhythmic with a single peak just before lights-on (ZT 23); however, while roughly half of the females (7/15) exhibited this clear daily rhythm, the remaining animals (8/15) had relatively high LQs that did not change as a function of time. Males had their shortest ejaculation latencies and their highest number of ejaculations at ZT 23. Rhythms in mount frequency and post-ejaculatory refractory period were bimodal, with peaks around lights-on and -off (ZT 23 and 11). This temporal pattern of mounting behavior closely parallels previously documented patterns of general activity, whereas rhythms in the more reflexive components of sex behavior (LQ and ejaculation) had more restricted peaks that coincided with just the onset of rhythms in general activity. These rhythms in sexual behavior are essentially reversed relative to those previously documented in lab rats.

  • Arginine vasopressin and vasoactive intestinal polypeptide fibers make appositions with gonadotropin-releasing hormone and estrogen receptor cells in the diurnal rodent Arvicanthis niloticus
    Brain Research, 2005
    Co-Authors: Megan M Mahoney, Laura Smale
    Abstract:

    Diurnal and nocturnal animals differ with respect to the timing of a host of behavioral and physiological events including those associated with estrus, but the neural bases of these differences have not been elucidated. We investigated this issue by examining the distribution of cells containing gonadotropin-releasing hormone (GnRH) as well as estrogen receptors (ERs) in relation to fibers containing peptides present in the suprachiasmatic nucleus (SCN) in a diurnal animal, Arvicanthis niloticus (the unstriped Nile grass rat). We found that fibers containing two peptides found in SCN cells, arginine vasopressin and vasoactive intestinal polypeptide appeared to be in contact with GnRH and ER positive cells. These data suggest that temporal information is carried along the same direct pathways from the SCN to GnRH and ER neurons in day- and night-active species.

  • effects of photoperiod on the reproductive condition of nile grass rats Arvicanthis niloticus from an equatorial population
    African Journal of Ecology, 2002
    Co-Authors: Scott Nunes, Teresa L. Mcelhinny, Megan M Mahoney, Laura Smale
    Abstract:

    We evaluated the effects of photoperiod on the reproductive condition of male and female Nile grass rats (Arvicanthis niloticus) descended from members of an equatorial population trapped 2°S of the equator. Study animals housed in 12:12 light:dark (LD) cycles were transferred either to short photoperiod (9:15) or long photoperiod (15:9) for 9 weeks (males) or 11 weeks (females), and various reproductive parameters were assessed. We observed no differences between short- and long-day males with respect to plasma concentration of testosterone, testicular mass, seminal vesicle mass, or spermatogenesis. Similarly, we observed no differences between short- and long-day females with respect to oestrous cycles, uterine mass, follicle size, or presence of corpora lutea. Reproductive parameters of male and female A. niloticus housed in short- and long photoperiods were similar to those typically observed among animals descended from the same equatorial population and housed in LD 12:12. Thus, photoperiod appears not to elicit changes in reproductive condition among A. niloticus from populations whose native habitat lies within 2° of the equator. These data contrast with the results of other studies indicating that photoperiod alters reproductive condition in A. niloticus populations living >10° from the equator. Resume Nous avons etudie les effets de la photoperiode sur la condition reproductive des mâles et des femelles des rats Arvicanthis niloticus, issus de membres d'une population equatoriale attrapee a 2° au sud de l'Equateur. Les animaux de l'etude soumis a des cycles 12 : 12 lumiere : obscurite (LD) ont ete transferes dans des conditions de photoperiodes courtes (9 : 15) ou longues (15 : 9) pendant 9 semaines (mâles) ou 11 semaines (femelles), et on a etudie les differents parametres de la reproduction. Nous n'avons constate aucune difference entre les mâles soumis aux jours longs ou courts, en ce qui concerne la concentration de testosterone dans le plasma, le poids des testicules, celui de la vesicule seminale ou la spermatogenese. De meme, nous n'avons observe aucune difference entre les femelles soumises aux jours longs ou courts en ce qui concerne le cycle oestral, le poids de l'uterus, la taille des follicules ou la presence de corps jaune. Les parametres reproducteurs des A. niloticus mâles et femelles soumis a des photoperiodes longues ou courtes etaient semblables a ceux que l'on observe classiquement chez les animaux issus de cette meme population equatoriale et loges dans des conditions LD 12 : 12. Il semble donc que la photoperiode ne suscite aucun changement de l'etat reproductif chez les A. niloticus issus de populations dont l'habitat original se situe a 2° sous l'Equateur. Ces donnees sont en contradiction avec les resultats d'autres etudes qui montraient que la photoperiode altere l'etat reproductif des populations de A. niloticus vivant a plus de 10° de l'Equateur.

Megan M Mahoney - One of the best experts on this subject based on the ideXlab platform.

  • Arginine vasopressin and vasoactive intestinal polypeptide fibers make appositions with gonadotropin-releasing hormone and estrogen receptor cells in the diurnal rodent Arvicanthis niloticus
    Brain Research, 2005
    Co-Authors: Megan M Mahoney, Laura Smale
    Abstract:

    Diurnal and nocturnal animals differ with respect to the timing of a host of behavioral and physiological events including those associated with estrus, but the neural bases of these differences have not been elucidated. We investigated this issue by examining the distribution of cells containing gonadotropin-releasing hormone (GnRH) as well as estrogen receptors (ERs) in relation to fibers containing peptides present in the suprachiasmatic nucleus (SCN) in a diurnal animal, Arvicanthis niloticus (the unstriped Nile grass rat). We found that fibers containing two peptides found in SCN cells, arginine vasopressin and vasoactive intestinal polypeptide appeared to be in contact with GnRH and ER positive cells. These data suggest that temporal information is carried along the same direct pathways from the SCN to GnRH and ER neurons in day- and night-active species.

  • a daily rhythm in mating behavior in a diurnal murid rodent Arvicanthis niloticus
    Hormones and Behavior, 2005
    Co-Authors: Megan M Mahoney, Laura Smale
    Abstract:

    The time of day at which mating occurs is dramatically different in diurnal compared to nocturnal rodents. We used a diurnal murid rodent, Arvicanthis niloticus, to determine if inverted rhythms in responsiveness to hormones contribute to this difference. Male and hormone-primed female grass rats were tested for mating behavior at four different times of day (ZT 5, 11, 17, 23; ZT 0=lights-on). In females, there was considerable inter-individual variability with respect to patterns of responsiveness to hormones. Overall, the lordosis quotient (LQ) was rhythmic with a single peak just before lights-on (ZT 23); however, while roughly half of the females (7/15) exhibited this clear daily rhythm, the remaining animals (8/15) had relatively high LQs that did not change as a function of time. Males had their shortest ejaculation latencies and their highest number of ejaculations at ZT 23. Rhythms in mount frequency and post-ejaculatory refractory period were bimodal, with peaks around lights-on and -off (ZT 23 and 11). This temporal pattern of mounting behavior closely parallels previously documented patterns of general activity, whereas rhythms in the more reflexive components of sex behavior (LQ and ejaculation) had more restricted peaks that coincided with just the onset of rhythms in general activity. These rhythms in sexual behavior are essentially reversed relative to those previously documented in lab rats.

  • effects of photoperiod on the reproductive condition of nile grass rats Arvicanthis niloticus from an equatorial population
    African Journal of Ecology, 2002
    Co-Authors: Scott Nunes, Teresa L. Mcelhinny, Megan M Mahoney, Laura Smale
    Abstract:

    We evaluated the effects of photoperiod on the reproductive condition of male and female Nile grass rats (Arvicanthis niloticus) descended from members of an equatorial population trapped 2°S of the equator. Study animals housed in 12:12 light:dark (LD) cycles were transferred either to short photoperiod (9:15) or long photoperiod (15:9) for 9 weeks (males) or 11 weeks (females), and various reproductive parameters were assessed. We observed no differences between short- and long-day males with respect to plasma concentration of testosterone, testicular mass, seminal vesicle mass, or spermatogenesis. Similarly, we observed no differences between short- and long-day females with respect to oestrous cycles, uterine mass, follicle size, or presence of corpora lutea. Reproductive parameters of male and female A. niloticus housed in short- and long photoperiods were similar to those typically observed among animals descended from the same equatorial population and housed in LD 12:12. Thus, photoperiod appears not to elicit changes in reproductive condition among A. niloticus from populations whose native habitat lies within 2° of the equator. These data contrast with the results of other studies indicating that photoperiod alters reproductive condition in A. niloticus populations living >10° from the equator. Resume Nous avons etudie les effets de la photoperiode sur la condition reproductive des mâles et des femelles des rats Arvicanthis niloticus, issus de membres d'une population equatoriale attrapee a 2° au sud de l'Equateur. Les animaux de l'etude soumis a des cycles 12 : 12 lumiere : obscurite (LD) ont ete transferes dans des conditions de photoperiodes courtes (9 : 15) ou longues (15 : 9) pendant 9 semaines (mâles) ou 11 semaines (femelles), et on a etudie les differents parametres de la reproduction. Nous n'avons constate aucune difference entre les mâles soumis aux jours longs ou courts, en ce qui concerne la concentration de testosterone dans le plasma, le poids des testicules, celui de la vesicule seminale ou la spermatogenese. De meme, nous n'avons observe aucune difference entre les femelles soumises aux jours longs ou courts en ce qui concerne le cycle oestral, le poids de l'uterus, la taille des follicules ou la presence de corps jaune. Les parametres reproducteurs des A. niloticus mâles et femelles soumis a des photoperiodes longues ou courtes etaient semblables a ceux que l'on observe classiquement chez les animaux issus de cette meme population equatoriale et loges dans des conditions LD 12 : 12. Il semble donc que la photoperiode ne suscite aucun changement de l'etat reproductif chez les A. niloticus issus de populations dont l'habitat original se situe a 2° sous l'Equateur. Ces donnees sont en contradiction avec les resultats d'autres etudes qui montraient que la photoperiode altere l'etat reproductif des populations de A. niloticus vivant a plus de 10° de l'Equateur.

  • phase response curve and light induced fos expression in the suprachiasmatic nucleus and adjacent hypothalamus of Arvicanthis niloticus
    Journal of Biological Rhythms, 2001
    Co-Authors: Megan M Mahoney, Abel Bult, Laura Smale
    Abstract:

    This article describes the phase response curve (PRC), the effect of light on Fos immunoreactivity (Fos-IR) in the suprachiasmatic nucleus (SCN), and the effect of SCN lesions on circadian rhythms in the murid rodent, Arvicanthis niloticus. In this species, all individuals are diurnal when housed without a running wheel, but running in a wheel induces a nocturnal pattern in some individuals. First, the authors characterized the PRC in animals with either the nocturnal or diurnal pattern. Both groups of animals were less affected by light during the middle of the subjective day than during the night and were phase delayed and phase advanced by pulses in the early and late subjective night, respectively. Second, the authors characterized the Fos response to light at circadian times 5, 14, or 22. Light induced an increase in Fos-IR within the SCN during the subjective night but not subjective day; this effect was especially pronounced in the ventral SCN, where retinal inputs are most concentrated, but was al...

  • phase response curve and light induced fos expression in the suprachiasmatic nucleus and adjacent hypothalamus of Arvicanthis niloticus
    Journal of Biological Rhythms, 2001
    Co-Authors: Megan M Mahoney, Abel Bult, Laura Smale
    Abstract:

    This article describes the phase response curve (PRC), the effect of light on Fos immunoreactivity (Fos-IR) in the suprachiasmatic nucleus (SCN), and the effect of SCN lesions on circadian rhythms in the murid rodent, Arvicanthis niloticus. In this species, all individuals are diurnal when housed without a running wheel, but running in a wheel induces a nocturnal pattern in some individuals. First, the authors characterized the PRC in animals with either the nocturnal or diurnal pattern. Both groups of animals were less affected by light during the middle of the subjective day than during the night and were phase delayed and phase advanced by pulses in the early and late subjective night, respectively. Second, the authors characterized the Fos response to light at circadian times 5, 14, or 22. Light induced an increase in Fos-IR within the SCN during the subjective night but not subjective day; this effect was especially pronounced in the ventral SCN, where retinal inputs are most concentrated, but was also evident in other regions. Both light and time influenced Fos-IR within the lower subparaventricular area. Third, SCN lesions caused animals to become arrhythmic when housed in a light-dark cycle as well as constant darkness. In summary, Arvicanthis appear to be very similar to nocturnal rodents with respect to their PRC, temporal patterns of light-induced Fos expression in the SCN, and the effects of SCN lesions on activity rhythms.

David Hicks - One of the best experts on this subject based on the ideXlab platform.

  • diurnal rodents as pertinent animal models of human retinal physiology and pathology
    Progress in Retinal and Eye Research, 2020
    Co-Authors: Daniela M Verra, Benjamin S Sajdak, Dana K Merriman, David Hicks
    Abstract:

    Abstract This presentation will survey the retinal architecture, advantages, and limitations of several lesser-known rodent species that provide a useful diurnal complement to rats and mice. These diurnal rodents also possess unusually cone-rich photoreceptor mosaics that facilitate the study of cone cells and pathways. Species to be presented include principally the Sudanian Unstriped Grass Rat and Nile Rat (Arvicanthis spp.), the Fat Sand Rat (Psammomys obesus), the degu (Octodon degus) and the 13-lined ground squirrel (Ictidomys tridecemlineatus). The retina and optic nerve in several of these species demonstrate unusual resilience in the face of neuronal injury, itself an interesting phenomenon with potential translational value.

  • blue light at night acutely impairs glucose tolerance and increases sugar intake in the diurnal rodent Arvicanthis ansorgei in a sex dependent manner
    Physiological Reports, 2019
    Co-Authors: David Hicks, Andries Kalsbeek, Anayanci Masisvargas, Jorge Mendoza
    Abstract:

    In our modern society, the exposure to light at night (LAN) has increased considerably, which may impact human health negatively. Especially exposure to light at night containing short wavelength emissions (~450-500 nm) can disrupt the normal function of the biological clock, altering sleep-wake cycles and inducing metabolic changes. Recently, we reported that light at night acutely impairs glucose tolerance in nocturnal rats. However, light at night in nocturnal rodents coincides with their activity period, in contrast to artificial light at night exposure in humans. The aim of this study was to evaluate the acute effects of blue (λ = 490 ± 20 nm) artificial light at night (bALAN) on glucose metabolism and food intake in both male and female diurnal Sudanian grass rats (Arvicanthis ansorgei) fed either regular chow or a free choice high-fat high sucrose diet (HFHS). In both chow and HFHS fed male Arvicanthis, 1-hour of bALAN exposure induced a higher glucose response in the oral glucose tolerance test (OGTT) accompanied by a significant decrease in plasma insulin. Furthermore, in HFHS fed animals, bALAN induced an increase in sucrose intake during the dark phase in males but not in females. Additionally, 1-h of bALAN increased the nonfasted glucose levels together with plasma corticosterone in female grass rats. These results provide new and further evidence for the deleterious effects of exposure to short wavelength emission-containing artificial light at night on glucose metabolism in a diurnal rodent in a sex-dependent manner.

  • unique regulation of the melatonin synthetic pathway in the retina of diurnal female Arvicanthis ansorgei rodentia
    Endocrinology, 2015
    Co-Authors: Coralie Gianesini, David Hicks, Daniel Clesse, Gianluca Tosini, Virginie Laurent
    Abstract:

    Knowledge about melatonin synthesis and its potential roles within the retina remains fragmented, especially in mammals where studies have focused on the penultimate enzyme of melatonin synthesis arylalkylamine N-acetyltransferase (AA-NAT), whereas the final enzyme necessary for melatonin production is hydroxyindole-O-methytransferase (HIOMT). We explored multiple parameters of the melatonin synthetic pathway in the cone-rich retina of a diurnal rodent, Arvicanthis ansorgei, cones being previously implicated as probable reservoirs of melatonin production. We analyzed the temporal and spatial expression of Aa-nat mRNA and AA-NAT protein and enzymatic activity of AA-NAT, HIOMT, as well as the melatonin receptor type 1 and melatonin itself. We report that Aa-nat mRNA was localized principally to cones and ganglion cells (retinal ganglion cell [RGC]) with opposing cyclic expression, being maximal in cones during the night, and maximal in RGC in the daytime. AA-NAT protein was also immunolocalized to these sam...

  • intrinsic photosensitive retinal ganglion cells in the diurnal rodent Arvicanthis ansorgei
    PLOS ONE, 2013
    Co-Authors: Diana Karnas, David Hicks, Paul Pévet, Jerome Mordel, Hilmar Meissl
    Abstract:

    Intrinsically photosensitive retinal ganglion cells (ipRGCs) represent a new class of photoreceptors which support a variety of non-image forming physiological functions, such as circadian photoentrainment, pupillary light reflex and masking responses to light. In view of the recently proposed role of retinal inputs for the regulation of diurnal and nocturnal behavior, we performed the first deep analysis of the ipRGC system in a diurnal rodent model, Arvicanthisansorgei, and compared the anatomical and physiological properties of ipRGCs with those of nocturnal mice. Based on somata location, stratification pattern and melanopsin expression, we identified two main ipRGC types in the retina of Arvicanthis: M1, constituting 74% of all ipRGCs and non-M1 (consisting mainly of the M2 type) constituting the following 25%. The displaced ipRGCs were rarely encountered. Phenotypical staining patterns of ganglion cell markers showed a preferential expression of Brn3 and neurofilaments in non-M1 ipRGCs. In general, the anatomical properties and molecular phenotyping of ipRGCs in Arvicanthis resemble ipRGCs of the mouse retina, however the percentage of M1 cells is considerably higher in the diurnal animal. Multi-electrode array recordings (MEA) identified in newborn retinas of Arvicanthis three response types of ipRGCs (type I, II and III) which are distinguished by their light sensitivity, response strength, latency and duration. Type I ipRGCs exhibited a high sensitivity to short light flashes and showed, contrary to mouse type I ipRGCs, robust light responses to 10 ms flashes. The morphological, molecular and physiological analysis reveals very few differences between mouse and Arvicanthis ipRGCs. These data imply that the influence of retinal inputs in defining the temporal niche could be related to a stronger cone input into ipRGCs in the cone-rich Arvicanthis retina, and to the higher sensitivity of type I ipRGCs and elevated proportion of M1 cells.

  • structural and physiological responses to prolonged constant lighting in the cone rich retina of Arvicanthis ansorgei
    Experimental Eye Research, 2010
    Co-Authors: Madah Khawn Muhammad I Mehdi, David Hicks
    Abstract:

    Cone photoreceptor death is a leading cause of blindness in industrialised countries. Despite this, there are few mammalian models available to study cone pathophysiology. The diurnal rodent Arvicanthis possesses a high cone percentage and ease of maintenance. We recently described the effect of ambient light conditions on cyclic disc shedding, and observed that 24 h of constant illumination ("LL") completely disrupted the normal rhythmic process and increased cone shedding fourfold. The current study was undertaken to see whether protracted constant illumination (7 days LL) would further perturb cone (and rod) turnover, and possibly lead to photoreceptor degeneration. Whereas control (cyclic lighting) retinas exhibited a typical early morning burst in phagosomes, LL retinas exhibited only low uniform numbers of rod and cone phagosomes across 24 h, with no peak of shedding at any time. Morphometric and immunohistochemical analyses of Arvicanthis retinas after 7 days LL (300 lux) showed no structural changes compared to control retinas.

Yves Sauve - One of the best experts on this subject based on the ideXlab platform.

  • retinorecipient areas in the diurnal murine rodent Arvicanthis niloticus a disproportionally large superior colliculus
    The Journal of Comparative Neurology, 2013
    Co-Authors: Frederic Gaillard, Harvey J Karten, Yves Sauve
    Abstract:

    The Nile grass rat (Arvicanthis niloticus) has a high proportion of cone photoreceptors (∼30–40%) compared with that in the common laboratory mouse and rat (∼1–3%) and may prove a preferable murine model with which to study cone-driven information processing in retina and primary visual centers. However, other than regions involved in circadian control, little is known about the retinorecipient structures in this rodent. We undertook a detailed analysis of the retinal projections as revealed after intravitreal injection of the anterograde tracer cholera toxin subunit B. Retinal efferents were evaluated in 45 subcortical structures. Contralateral projections were always dominant. Major contralateral inputs consisted of the suprachiasmatic nucleus, dorsolateral geniculate nucleus (dLGN), intergeniculate leaflet, ventral geniculate nucleus (magnocellular part), lateroposterior thalamic nucleus, all six pretectal nuclei, superficial layers of the superior colliculus (SC), and the main nuclei of the accessory optic system. Terminals from the contralateral eye were also localized in an unnamed field rostromedial to the dLGN as well as in the subgeniculate thalamic nucleus. Ipsilateral inputs were found mainly in the suprachiasmatic nucleus, dLGN, intergeniculate leaflet, internal sector of the magnocellular part of the ventral geniculate nucleus, olivary pretectal nucleus, and SC optic layer. Retinal afferents were not detected in the basal forebrain or the dorsal raphe nucleus. Morphometric measurements revealed that the superficial layers of the SC are disproportionately enlarged relative to other retinorecipient regions and brain size compared with rats and mice. We suggest that this reflects the selective projection of cone-driven retinal ganglion cells to the SC. J. Comp. Neurol. 521:1699–1726, 2013. © 2012 Wiley Periodicals, Inc.

  • the electroretinogram erg of a diurnal cone rich laboratory rodent the nile grass rat Arvicanthis niloticus
    Vision Research, 2008
    Co-Authors: Gregory S Gilmour, Frederic Gaillard, Juliane Watson, Sharee Kuny, Silvina C Mema, Stephan Bonfield, William K Stell, Yves Sauve
    Abstract:

    The most widespread models to study blindness, rats and mice, have retinas containing less than 3% cones. The diurnal rodent Arvicanthis niloticus retina has around 35% cones. Using ERG recordings, we studied retina function in this species. Several features differed from that reported in rats and mice: (a) fivefold larger photopic a-wave amplitudes; (b) photopic hill effect in Nile grass rats only; and (c) flicker amplitude plateau between 5 to 35 Hz with fusion beyond 60 Hz in Nile grass rats only. We conclude that A. niloticus might complement rats and mice for studying retinal function and pathologies involving cones.

  • retinal anatomy and visual performance in a diurnal cone rich laboratory rodent the nile grass rat Arvicanthis niloticus
    The Journal of Comparative Neurology, 2008
    Co-Authors: Frederic Gaillard, Laura Smale, Gregory S Gilmour, Sharee Kuny, Silvina C Mema, Stephan Bonfield, William K Stell, Brent T Martin, Nathan A Crowder, Yves Sauve
    Abstract:

    Unlike laboratory rats and mice, muridae of the Arvicanthis family (A. ansorgei and A. niloticus) are adapted to functioning best in daylight. To date, they have been used as experimental models mainly in studies of circadian rhythms. However, recent work aimed at optimizing photoreceptor-directed gene delivery vectors (Khani et al. [2007] Invest Ophthalmol Vis Sci 48:3954-3961) suggests their potential usefulness for studying retinal pathologies and therapies. In the present study we analyzed the retinal anatomy and visual performance of the Nile grass rat (A. niloticus) using immunohistofluorescence and the optokinetic response (OKR). We found that approximately 35-40% of photoreceptors are cones; that many neural features of the inner retina are similar to those in other diurnal mammals; and that spatial acuity, measured by the OKR, is more than two times that of the usual laboratory rodents. These observations are consistent with the known diurnal habits of this animal, and further support its pertinence as a complementary model for studies of structure, function, and pathology in cone-rich mammalian retinae.

Teresa L. Mcelhinny - One of the best experts on this subject based on the ideXlab platform.

  • effects of photoperiod on the reproductive condition of nile grass rats Arvicanthis niloticus from an equatorial population
    African Journal of Ecology, 2002
    Co-Authors: Scott Nunes, Teresa L. Mcelhinny, Megan M Mahoney, Laura Smale
    Abstract:

    We evaluated the effects of photoperiod on the reproductive condition of male and female Nile grass rats (Arvicanthis niloticus) descended from members of an equatorial population trapped 2°S of the equator. Study animals housed in 12:12 light:dark (LD) cycles were transferred either to short photoperiod (9:15) or long photoperiod (15:9) for 9 weeks (males) or 11 weeks (females), and various reproductive parameters were assessed. We observed no differences between short- and long-day males with respect to plasma concentration of testosterone, testicular mass, seminal vesicle mass, or spermatogenesis. Similarly, we observed no differences between short- and long-day females with respect to oestrous cycles, uterine mass, follicle size, or presence of corpora lutea. Reproductive parameters of male and female A. niloticus housed in short- and long photoperiods were similar to those typically observed among animals descended from the same equatorial population and housed in LD 12:12. Thus, photoperiod appears not to elicit changes in reproductive condition among A. niloticus from populations whose native habitat lies within 2° of the equator. These data contrast with the results of other studies indicating that photoperiod alters reproductive condition in A. niloticus populations living >10° from the equator. Resume Nous avons etudie les effets de la photoperiode sur la condition reproductive des mâles et des femelles des rats Arvicanthis niloticus, issus de membres d'une population equatoriale attrapee a 2° au sud de l'Equateur. Les animaux de l'etude soumis a des cycles 12 : 12 lumiere : obscurite (LD) ont ete transferes dans des conditions de photoperiodes courtes (9 : 15) ou longues (15 : 9) pendant 9 semaines (mâles) ou 11 semaines (femelles), et on a etudie les differents parametres de la reproduction. Nous n'avons constate aucune difference entre les mâles soumis aux jours longs ou courts, en ce qui concerne la concentration de testosterone dans le plasma, le poids des testicules, celui de la vesicule seminale ou la spermatogenese. De meme, nous n'avons observe aucune difference entre les femelles soumises aux jours longs ou courts en ce qui concerne le cycle oestral, le poids de l'uterus, la taille des follicules ou la presence de corps jaune. Les parametres reproducteurs des A. niloticus mâles et femelles soumis a des photoperiodes longues ou courtes etaient semblables a ceux que l'on observe classiquement chez les animaux issus de cette meme population equatoriale et loges dans des conditions LD 12 : 12. Il semble donc que la photoperiode ne suscite aucun changement de l'etat reproductif chez les A. niloticus issus de populations dont l'habitat original se situe a 2° sous l'Equateur. Ces donnees sont en contradiction avec les resultats d'autres etudes qui montraient que la photoperiode altere l'etat reproductif des populations de A. niloticus vivant a plus de 10° de l'Equateur.

  • Patterns of Wheel Running Are Related to Fos Expression in Neuropeptide-Y-Containing Neurons in the Intergeniculate Leaflet of Arvicanthis niloticus
    Journal of Biological Rhythms, 2001
    Co-Authors: Laura Smale, Teresa L. Mcelhinny, Joshua P. Nixon, Betty Gubik, Sandra Rose
    Abstract:

    A variety of nonphotic influences on circadian rhythms have been documented in mammals. In hamsters, one such influence, running in a novel wheel, is mediated in part by the pathway extending from neuropeptide-Y (NPY)-containing cells within the intergeniculate leaflet (IGL) of the thalamus to the hypothalamic suprachiasmatic nucleus (SCN). Arvicanthis niloticus is a species in which all individuals are diurnal with respect to general activity and body temperature when they are housed without a running wheel, but access to a running wheel induces a subset of individuals to become nocturnal. In the first study, the authors evaluated the possibility that nocturnal and diurnal patterns of wheel running in Arvicanthis are correlated with differences in IGL function. Adult male Arvicanthis housed in a 12:12 light-dark (LD) cycle were monitored in wheels, classified as nocturnal or diurnal, and then perfused either 4 h after lights-on or 4 h after lights-off. Sections through the intergeniculate leaflet were processed for immunohistochemical labeling of Fos and NPY. The percentage of NPY cells that expressed Fos was significantly influenced by an interaction between time of day and phenotype such that it rose from night to day in diurnal animals, and from day to night in nocturnal animals. In the second experiment, the authors established that running in a wheel actually induces Fos in the IGL of Arvicanthis. Specifically, the proportion of NPY cells expressing Fos was increased by access to wheels in nocturnal animals at night and in diurnal animals during the day. In the third experiment, the authors established that lesions of the IGL eliminate NPY fibers within the SCN, suggesting that these IGL cells project to the SCN in this species as has been established in other rodents. Together, these data demonstrate a clear difference in NPY cell function in nocturnal and diurnal Arvicanthis that appears to be caused, at least in part, by the differences in their wheel-running patterns, and that NPY cells within the IGL project to the SCN in Arvicanthis.

  • A Morning Surge in Plasma Luteinizing Hormone Coincides with Elevated Fos Expression in Gonadotropin-Releasing Hormone-Immunoreactive Neurons in the Diurnal Rodent, Arvicanthis niloticus
    Biology of Reproduction, 1999
    Co-Authors: Teresa L. Mcelhinny, Cheryl L. Sisk, Kay E. Holekamp, Laura Smale
    Abstract:

    Arvicanthis niloticus is a diurnal murid rodent from sub-Saharan Africa. Here we report on processes associated with mating in this species in an attempt to elucidate how the neural mechanisms governing temporal organization differ in nocturnal and diurnal species. First, we systematically mapped the distribution of GnRH neurons in adult females. Second, we tested the hypothesis that Arvicanthis differ from nocturnal murid rodents with respect to the timing of the LH surge and the associated increase in Fos expression in GnRH-immunoreactive (IR) neurons. We examined these events around a postpartum estrus. When parturition occurred between zeitgeber time (ZT) 2 and 17 (lights on at ZT 0 and off at ZT 12; there are 24 ZT units a day, each equivalent to 1 standard hour), we collected blood and perfused females at ZT 17, 20, 23, or 2. A sharp peak in plasma LH occurred at ZT 20, and a 10-fold increase in the percentage of GnRH-IR neurons that expressed Fos-IR occurred between ZT 17 and 20. By contrast, this rise occurs in nocturnal rodents during the last few hours of the light period. This is the first indication of a difference between nocturnal and diurnal animals with respect to neural mechanisms associated with a precisely timed event of known significance.

  • nocturnal and diurnal rhythms in the unstriped nile rat Arvicanthis niloticus
    Journal of Biological Rhythms, 1999
    Co-Authors: J A Blanchong, Teresa L. Mcelhinny, Megan M Mahoney, Laura Smale
    Abstract:

    In a laboratory population of unstriped Nile grass rats, Arvicanthis niloticus, individuals with two distinctly different patterns of wheel-running exist. One is diurnal and the other is relatively nocturnal. In the first experiment, the authors found that these patterns are strongly influenced by parentage and by sex. Specifically, offspring of two nocturnal parents were significantly more likely to express a nocturnal pattern of wheel-running than were offspring of diurnal parents, and more females than males were nocturnal. In the second experiment, the authors found that diurnal and nocturnal wheel-runners were indistinguishable with respect to the timing of postpartum mating, which always occurred in the hours before lights-on. Here they also found that both juvenile and adult A. niloticus exhibited diurnal patterns of general activity when housed without a wheel, even if they exhibited nocturnal activity when housed with a wheel. In the third experiment, the authors discovered that adult female A. niloticus with nocturnal patterns of wheel-running were also nocturnal with respect to general activity and core body temperature when a running wheel was available, but they were diurnal when the running wheel was removed. Finally, a field study revealed that all A. niloticus were almost exclusively diurnal in their natural habitat. Together these results suggest that individuals of this species are fundamentally diurnal but that access to a running wheel shifts some individuals to a nocturnal pattern.

  • patterns of body temperature activity and reproductive behavior in a tropical murid rodent Arvicanthis niloticus
    Physiology & Behavior, 1997
    Co-Authors: Teresa L. Mcelhinny, Laura Smale, Kay E. Holekamp
    Abstract:

    Abstract M c Elhinny, T. L., L. Smale and K. E. Holekamp. Patterns of body temperature, activity, and reproductive behavior in a tropical murid rodent, Arvicanthis niloticus. Physiol Behav 62(1) 91–96, 1997.—Nile grass rats ( Arvicanthis niloticus ), are murid rodents from tropical Africa that exhibit diurnal patterns of wheel-running. In the present paper we describe the temporal organization of several other behaviors in these animals, as well as daily rhythms in their body temperature. In the first experiment, we characterized rhythms of gross motor activity and core body temperature in four adult females implanted with telemetry transmitters and kept on a 12:12 light:dark (LD) cycle. In all animals body temperature and gross motor activity were clearly diurnal, with peaks often occurring around dawn and dusk. In the second experiment we recorded the times of mating and parturition in eight mating couples housed in a 12:12 LD cycle. We monitored animals 24 h a day using a time-lapse video recording system, beginning when males and females were paired, and ending after the birth of the second litter and the associated post-partum copulation. Mating almost always began just before the lights came on, and parturition generally occurred in an “anticrepuscular” pattern, outside of the periods around dawn and dusk. Thus, these animals exhibit an interesting mosaic of temporal adaptations, with some crepuscular tendencies expressed within a predominantly diurnal pattern.

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