The Experts below are selected from a list of 1428 Experts worldwide ranked by ideXlab platform
John R Okusky - One of the best experts on this subject based on the ideXlab platform.
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increased expression of insulin like growth factor i augments the progressive phase of synaptogenesis without preventing synapse elimination in the Hypoglossal Nucleus
The Journal of Comparative Neurology, 2003Co-Authors: John R Okusky, Joseph A DercoleAbstract:The in vivo actions of insulin-like growth factor I (IGF-I) on synaptogenesis in the Hypoglossal Nucleus were investigated in transgenic mice that overexpress IGF-I in the brain postnatally and in normal nontransgenic littermate controls. In a previous study using these mice, we found that IGF-I increases the total volume of the Hypoglossal Nucleus by increasing the volume of neuropil rather than by increasing total neuron number; therefore, the progressive and regressive phases of synaptogenesis could be evaluated without the confounding effects of altered neuron number. The volume of the Hypoglossal Nucleus was significantly increased by 28% to 59% in transgenic mice after postnatal day (P) 7, whereas the total number of Hypoglossal neurons did not differ significantly from controls. The numerical density of neurons was significantly decreased by 21% to 38% after P7, and the density of myelinated axons was significantly increased by 19%. Although the numerical density of synapses did not differ between groups at any age, the total number of synapses in transgenic mice was increased by 42% to 52% after P14. Total synapse number in controls increased from P7 (7.9 million) to peak values at P21 (36.0 million), followed by a significant decrease (33%) at P130 (24.2 million). In transgenic mice, total synapses increased from 8.2 million on P7 to 51.1 million on P21, followed by a significant decrease (28%) to 36.7 million at P130. Our results demonstrated that IGF-I can stimulate a persistent increase in the number of Hypoglossal synapses, thereby augmenting the progressive phase of synaptogenesis without preventing synapse elimination during the regressive phase. J. Comp. Neurol. 464:382–391, 2003. © 2003 Wiley-Liss, Inc.
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postnatal changes in the numerical density and total number of asymmetric and symmetric synapses in the Hypoglossal Nucleus of the rat
Developmental Brain Research, 1998Co-Authors: John R OkuskyAbstract:Abstract Morphometric analyses were performed to investigate the progressive and regressive phases of synaptogenesis in the Hypoglossal Nucleus of the rat during normal postnatal development. The total volume of the Hypoglossal Nucleus and both the numerical density (NV, contacts per mm3) and total number of synapses were measured at 5-day intervals from birth to postnatal day 30 and in young adults. Values of NV were calculated separately for asymmetric and symmetric synapses as well as for axospinous, axodendritic and axosomatic contacts. The volume of the Hypoglossal Nucleus increased significantly from birth to postnatal day 30 (414%) with no further increase in the adult. The NV of all synapses increased significantly from birth to day 20 (131%), followed by a significant decrease in adults (45%). The total number of synapses increased significantly from birth to day 20 (843%), followed by a significant decrease in adults (30%). Similar developmental changes in density and total number were observed for asymmetric and symmetric synapses. The magnitude of synapse elimination, occurring after day 20, was approximately 30% for both morphological types. During postnatal development the vast majority of synapses in the Hypoglossal Nucleus were found to form axodendritic contacts (85–95%). Synapse elimination was observed for axospinous, axodendritic and axosomatic contacts. These findings indicate that the progressive and regressive phases of synaptogenesis occur earlier in the Hypoglossal Nucleus than in the cerebral cortex of the rat, suggesting a caudal-to-rostral gradient. Synapse elimination was not restricted on the basis of morphological type or postsynaptic target site.
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sudden infant death syndrome increased number of synapses in the Hypoglossal Nucleus
Journal of Neuropathology and Experimental Neurology, 1995Co-Authors: John R Okusky, Margaret G NormanAbstract:The medulla was sampled from nine cases of sudden infant death syndrome (SIDS) and from six age-matched control cases without neurological disease. Morphometric analyses were performed on serial Nissl sections through the Hypoglossal Nucleus on the left side of the medulla. The total volume of the Nucleus and both the numerical density (Nv, cells per mm3) and total number of neurons were measured. Tissue from the remaining Hypoglossal Nucleus was prepared for electron microscopy using the ethanolic phosphotungstic acid method to stain synaptic contacts. Stereological analyses were performed to determine the Nv and total number of synapses. Total volume of the Hypoglossal Nucleus was significantly greater (36%) in SIDS cases than in controls. The Nv of neurons was significantly less than in controls (28%), although the total number of neurons did not differ significantly. The mean profile area of motor neuron cell bodies was significantly greater (30%) in SIDS cases, with no differences in the mean profile areas for interneurons or glia. The Nv of synapses did not differ significantly between SIDS cases and controls, although the total number of synapses was greater (61%) in SIDS. These abnormalities in growth indicate a greater volume of neuropil in a Hypoglossal Nucleus containing a normal complement of neurons. The greater number of synapses in SIDS cases is consistent with a failure to eliminate normally extraneous synapses during early development.
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sudden infant death syndrome postnatal changes in the numerical density and total number of neurons in the Hypoglossal Nucleus
Journal of Neuropathology and Experimental Neurology, 1992Co-Authors: John R Okusky, Margaret G NormanAbstract:Tissue specimens from the medulla were sampled from 28 sudden infant death syndrome (SIDS) victims and from 15 control cases without neurological disease (36-95 postconceptional weeks). Morphometric analyses were performed on serial Nissl sections through the Hypoglossal Nucleus. The total volume of the Hypoglossal Nucleus, the numerical density (Nv, cells per mm3) and the total number of motor neurons, interneurons and glia were determined. Normal development was characterized by a linear increase in the volume of the Hypoglossal Nucleus during the first postnatal year. While the Nv of neurons decreased, the total number of neurons remained relatively constant at approximately 7,600 motor neurons and 3,100 interneurons. In SIDS cases the rate of increase in the volume of the Hypoglossal Nucleus was significantly greater than in controls (79%). The Nv of neurons was less than in controls (25-30%), although the total number of motor neurons and interneurons did not differ significantly. In SIDS cases the mean profile area of motor neuron cell bodies was significantly greater than in controls (29%), while the mean profile areas of interneurons and glia did not differ. These abnormalities in growth indicate a greater volume of neuropil in a Hypoglossal Nucleus containing a normal complement of neurons. The disproportionately rapid increase in volume of neuropil in the Hypoglossal Nucleus of SIDS cases may result from an increased arborization of dendrites on the motor neurons.
Jian Kang - One of the best experts on this subject based on the ideXlab platform.
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transient upregulation of task 1 expression in the Hypoglossal Nucleus during chronic intermittent hypoxia is reduced by serotonin 2a receptor antagonist
Journal of Cellular Physiology, 2019Co-Authors: Aidi Wang, Wei Wang, Hongyu Jin, Ying Zou, Zanfeng Wang, Jian KangAbstract:Hypoglossal motoneurons innervate genioglossus muscle, the contraction of which is critical in the maintenance of upper airway patency in patients with obstructive sleep apnea. As a potassium channel distributed in Hypoglossal motoneurons, TWIK-related acid-sensitive K+ channel-1 (TASK-1) could be inhibited by 5-HT. This study aimed to investigate if TASK-1 expression in Hypoglossal Nucleus could be influenced by chronic intermittent hypoxia (CIH) and 5-HT2A receptors antagonist. Two hundred twenty-eight rats were exposed to CIH or normoxia (NO) in the presence and absence of 5-HT 2A receptor antagonist (MDL-100907) microinjected into the Hypoglossal Nucleus. The expression of 5-HT and TASK-1 in the Hypoglossal Nucleus were detected by immunohistochemistry and reverse transcription quantitative polymerase chain reaction on the 1st, 3rd, 7th, 14th and 21st day of CIH exposure. The mean optical density (MOD) of 5-HT in the XII Nucleus was significantly increased in the CIH and CIH + MDL group than the NO group on the 7th and 21st day ( p < 0.05). Compared with the NO group, the MOD and gene expression of TASK-1 in the CIH group was significantly increased on the 7th and 14th day ( p < 0.05), then normalized on the 21st day. The TASK-1 expression in the CIH + MDL group was significantly lower than the CIH + PBS and CIH group on the 7th and 14th day ( p < 0.05). The CIH-induced transiently upregulation of the TASK-1 expression in the Hypoglossal Nucleus could be reversed by 5-HT 2A receptor antagonist, indicating that the modulation of the TASK-1 expression in response to CIH involves 5-HT and 5-HT 2A receptors, and this CIH effect might be 5-HT 2A receptor-dependent.
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Noradrenergic Activation of Hypoglossal Nucleus Modulates the Central Regulation of Genioglossus in Chronic Intermittent Hypoxic Rats
Frontiers in neurology, 2017Co-Authors: Xinshi Nie, Wei Wang, Hongyu Jin, Ling Zhou, Aidi Wang, Jian Pang, Qin Zheng, Jian KangAbstract:Neuromuscular compensation of the genioglossus muscle can be induced by chronic intermittent hypoxia (CIH) in obstructive sleep apnea to maintain upper airway stability. Noradrenergic activation of Hypoglossal Nucleus plays a critical role in the central control of the genioglossus. However, it remains unknown whether norepinephrine (NE) takes part in the central regulation of the genioglossus during CIH. Adult male Wister rats (n = 32) were studied to explore the influence of noradrenergic activation of Hypoglossal Nucleus on the central control of the genioglossus at different stages of CIH. The rats were divided into four groups; normal control or normoxic (NO) group, CIH group, CIH + normal saline (NS) group, and CIH + prazosin (PZ, α1-adrenergic antagonist) group. Prasozin (0.2 mM, 60 nl) and NS (0.9%, 60 nl) were microinjected into the Hypoglossal Nucleus. The responses of the genioglossus corticomotor area to transcranial magnetic stimulation (TMS) were recorded on the 1st, 7th, 14th, and 21st day of CIH. The CIH group showed significantly shorter TMS latencies on days 1, 7, and 14 (3.85 ± 0.37 ms vs. 4.58 ± 0.42 ms, 3.93 ± 0.17 ms vs. 4.49 ± 0.55 ms, 3.79 ± 0.38 ms vs. 4.39 ± 0.30 ms, P < 0.05), and higher TMS amplitudes on day 1 (2.74 ± 0.87 mV vs. 1.60 ± 0.52 mV, P < 0.05) of CIH than the NO group. Compared to the CIH + NS group, the CIH + PZ group showed decreased TMS responses (longer latencies and lower amplitudes) only on the 14th day of CIH (3.99 ± 0.28 ms vs. 4.61±0.48 ms, 2.51 ± 0.67 mV vs. 1.18 ± 0.62 mV, P < 0.05). These results indicated that noradrenergic activation of the Hypoglossal Nucleus played a role in the central compensation of genioglossus through α1-adrenoceptor on the 14th day of CIH.
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Noradrenergic Activation of Hypoglossal Nucleus Modulates the Central Regulation of Genioglossus in Chronic Intermittent Hypoxic Rats
Frontiers Media S.A., 2017Co-Authors: Wei Wang, Hongyu Jin, Xinshi Nie, Ling Zhou, Aidi Wang, Zheng Qin, Jian Pang, Jian KangAbstract:Neuromuscular compensation of the genioglossus muscle can be induced by chronic intermittent hypoxia (CIH) in obstructive sleep apnea to maintain upper airway stability. Noradrenergic activation of Hypoglossal Nucleus plays a critical role in the central control of the genioglossus. However, it remains unknown whether norepinephrine takes part in the central regulation of the genioglossus during CIH. Adult male Wistar rats (n = 32) were studied to explore the influence of noradrenergic activation of Hypoglossal Nucleus on the central control of the genioglossus at different stages of CIH. The rats were divided into four groups: normal control or normoxic (NO) group, CIH group, CIH + normal saline (NS) group, and CIH + prazosin (PZ, α1-adrenergic antagonist) group. PZ (0.2 mM, 60 nl) and NS (0.9%, 60 nl) were microinjected into the Hypoglossal Nucleus. The responses of the genioglossus corticomotor area to transcranial magnetic stimulation (TMS) were recorded on the 1st, 7th, 14th, and 21st day of CIH. The CIH group showed significantly shorter TMS latencies on days 1, 7, and 14 (3.85 ± 0.37 vs. 4.58 ± 0.42, 3.93 ± 0.17 vs. 4.49 ± 0.55, 3.79 ± 0.38 vs. 4.39 ± 0.30 ms, P < 0.05), and higher TMS amplitudes on day 1 (2.74 ± 0.87 vs. 1.60 ± 0.52 mV, P < 0.05) of CIH than the NO group. Compared to the CIH + NS group, the CIH + PZ group showed decreased TMS responses (longer latencies and lower amplitudes) only on the 14th day of CIH (3.99 ± 0.28 vs. 4.61 ± 0.48 ms, 2.51 ± 0.67 vs. 1.18 ± 0.62 mV, P < 0.05). These results indicated that noradrenergic activation of the Hypoglossal Nucleus played a role in the central compensation of genioglossus through α1-adrenoceptor on the 14th day of CIH
Margaret G Norman - One of the best experts on this subject based on the ideXlab platform.
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sudden infant death syndrome increased number of synapses in the Hypoglossal Nucleus
Journal of Neuropathology and Experimental Neurology, 1995Co-Authors: John R Okusky, Margaret G NormanAbstract:The medulla was sampled from nine cases of sudden infant death syndrome (SIDS) and from six age-matched control cases without neurological disease. Morphometric analyses were performed on serial Nissl sections through the Hypoglossal Nucleus on the left side of the medulla. The total volume of the Nucleus and both the numerical density (Nv, cells per mm3) and total number of neurons were measured. Tissue from the remaining Hypoglossal Nucleus was prepared for electron microscopy using the ethanolic phosphotungstic acid method to stain synaptic contacts. Stereological analyses were performed to determine the Nv and total number of synapses. Total volume of the Hypoglossal Nucleus was significantly greater (36%) in SIDS cases than in controls. The Nv of neurons was significantly less than in controls (28%), although the total number of neurons did not differ significantly. The mean profile area of motor neuron cell bodies was significantly greater (30%) in SIDS cases, with no differences in the mean profile areas for interneurons or glia. The Nv of synapses did not differ significantly between SIDS cases and controls, although the total number of synapses was greater (61%) in SIDS. These abnormalities in growth indicate a greater volume of neuropil in a Hypoglossal Nucleus containing a normal complement of neurons. The greater number of synapses in SIDS cases is consistent with a failure to eliminate normally extraneous synapses during early development.
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sudden infant death syndrome postnatal changes in the numerical density and total number of neurons in the Hypoglossal Nucleus
Journal of Neuropathology and Experimental Neurology, 1992Co-Authors: John R Okusky, Margaret G NormanAbstract:Tissue specimens from the medulla were sampled from 28 sudden infant death syndrome (SIDS) victims and from 15 control cases without neurological disease (36-95 postconceptional weeks). Morphometric analyses were performed on serial Nissl sections through the Hypoglossal Nucleus. The total volume of the Hypoglossal Nucleus, the numerical density (Nv, cells per mm3) and the total number of motor neurons, interneurons and glia were determined. Normal development was characterized by a linear increase in the volume of the Hypoglossal Nucleus during the first postnatal year. While the Nv of neurons decreased, the total number of neurons remained relatively constant at approximately 7,600 motor neurons and 3,100 interneurons. In SIDS cases the rate of increase in the volume of the Hypoglossal Nucleus was significantly greater than in controls (79%). The Nv of neurons was less than in controls (25-30%), although the total number of motor neurons and interneurons did not differ significantly. In SIDS cases the mean profile area of motor neuron cell bodies was significantly greater than in controls (29%), while the mean profile areas of interneurons and glia did not differ. These abnormalities in growth indicate a greater volume of neuropil in a Hypoglossal Nucleus containing a normal complement of neurons. The disproportionately rapid increase in volume of neuropil in the Hypoglossal Nucleus of SIDS cases may result from an increased arborization of dendrites on the motor neurons.
Mary Behan - One of the best experts on this subject based on the ideXlab platform.
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the effect of age and tongue exercise on bdnf and trkb in the Hypoglossal Nucleus of rats
Behavioural Brain Research, 2012Co-Authors: Allison J Schaser, Kyle Michael Stang, Nadine P Connor, Mary BehanAbstract:Abstract Age-associated changes in tongue musculature may contribute to dysphagia. One possible treatment is tongue exercise. Exercise induces synaptic plasticity by increasing neurotrophic factors in spinal cord and limb musculature. However, effects of exercise on neurotrophic factors in the cranial sensorimotor system are unknown. Our purpose was to examine the effects of age and exercise on brain-derived neurotrophic factor (BDNF) and its receptor TrkB in the rat Hypoglossal Nucleus. Young, middle-aged, and old rats were assigned to exercise or no-exercise control conditions. Exercise animals were trained to perform a tongue press task for 8 weeks. Samples from the Hypoglossal Nucleus were analyzed for BDNF and TrkB immunoreactivity. Baseline maximum tongue forces were similar in all age groups and increased significantly following exercise. BDNF immunoreactivity did not show a significant decrease with age in control group. However, in the exercise group, BDNF was significantly increased in young animals. TrkB immunoreactivity decreased significantly with age in control group, but did not change with exercise. BDNF and TrkB immunoreactivity levels were positively correlated with exercise in young and middle aged animals, but were negatively or weakly correlated with exercise in old animals and with a lack of exercise in no-exercise controls. Tongue exercise was associated with increased tongue forces in rats at all ages. While increases in BDNF and TrkB levels associated with exercise may play a role in mechanisms contributing to increased tongue forces in young and middle-aged rats, other mechanisms may be involved in increased tongue forces observed in old rats.
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serotonergic projections from the caudal raphe nuclei to the Hypoglossal Nucleus in male and female rats
Respiratory Physiology & Neurobiology, 2009Co-Authors: Jessica R Barker, Cathy F Thomas, Mary BehanAbstract:The respiratory control system is sexually dimorphic. In many brain regions, including respiratory motor nuclei, serotonin (5HT) levels are higher in females than in males. We hypothesized that there could be sex differences in 5HT input to the Hypoglossal Nucleus, a region of the brainstem involved in upper airway control. Adult Fischer 344 rats were anesthetized and a retrograde transsynaptic neuroanatomical tracer, Bartha pseudorabies virus (PRV), was injected into the tongue. Sections through the medulla were reacted immunocytochemically for the presence of (i) PRV, (ii) tryptophan hydroxylase (TPH; marker of 5HT neurons), (iii) PRV combined with TPH, and (iv) 5HT. Sex hormone levels were measured in female rats and correlated with TPH immunoreactivity, as Hypoglossal 5HT levels vary with the estrous cycle. The number of PRV neurons was comparable in male and female rats. The number and distribution of TPH immunoreactive neurons in the caudal raphe nuclei were similar in male and female rats. The subset of 5HT neurons that innervate Hypoglossal motoneurons was also similar in male and female rats. With the exception of the ventrolateral region of the Hypoglossal Nucleus, 5HT immunoreactivity was similar in male and female rats. These data suggest that sex differences in 5HT modulation of Hypoglossal motoneurons in male and female rats are not the result of sex differences in TPH or 5HT, but may result from differences in neurotransmitter release and reuptake, location of 5HT synaptic terminals on Hypoglossal motoneurons, pre- and postsynaptic 5HT receptor expression, or the distribution of sex hormone receptors on Hypoglossal or caudal raphe neurons.
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Age-related Changes in the Serotonin 2A Receptor in the Hypoglossal Nucleus of Male and Female Rats
Respiratory physiology & neurobiology, 2007Co-Authors: Benjamin R. Seebart, Ryan T. Stoffel, Mary BehanAbstract:Hypoglossal motoneuron output to the genioglossus muscle contributes to upper airway patency. Serotonin (5HT) plays an important role in regulating Hypoglossal motoneuron excitability via serotonin 2A receptors (5HT2A). The purpose of this study was to investigate whether there are age-associated changes in 5HT2A receptor expression in the Hypoglossal Nucleus of male and female rats. The brains of young, middle-aged and old F344 rats were sectioned, reacted immunocytochemically for the presence of 5HT2A receptor, and the staining density quantified. The estrus stage of female rats was determined and circulating sex hormone levels measured and correlated with 5HT2A levels. The results show that there was significantly greater 5HT2A receptor immunoreactivity in the Hypoglossal Nucleus of female than of male rats. With increasing age, there was an increase in 5HT2A receptor immunoreactivity in the Hypoglossal Nucleus of female rats, whereas no age-associated changes were observed in male rats. Previous studies have shown a reduction in 5HT-dependent respiratory plasticity and an age-associated decrease in 5HT in the Hypoglossal Nucleus in male but not female rats. Data from the present study suggest that aging male rats fail to compensate adequately for reduced 5HT in the Hypoglossal Nucleus by upregulating the expression of the 5HT2A receptor.
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age and gender effects on serotonergic innervation and modulation of the Hypoglossal motor Nucleus
Respiratory Research, 2001Co-Authors: Mary Behan, A G Zabka, Gordon S MitchellAbstract:Aging results in structural, functional and neurochemical alterations in the respiratory system. Serotonin (5HT) plays a major role in breathing and the control of upper airway function. We tested the hypothesis that with increasing age there is a selective decrease in serotonergic modulation of respiratory motoneurons, in particular Hypoglossal motoneurons to the tongue in male rats. We used light microscopic immunocytochemistry to study the distribution of 5HT axons and boutons throughout the Hypoglossal Nucleus in young and old rats male and female rats. Aged male rats (>12 months) had fewer serotonin immunoreactive axons and boutons in the Hypoglossal Nucleus than young male rats (<6 months). In contrast, 5HT immunoreactivity in the Hypoglossal Nucleus in female rats was higher than in age-matched males, and increased with age. In order to assess the functional consequences of this anatomical reorganization, we measured long term facilitation (LTF), a serotonin-dependent, long lasting increase in respiratory motor output following episodic hypoxia. LTF in the Hypoglossal motor output was significantly reduced in aged male rats by comparison with young male rats [1]. In contrast, Hypoglossal LTF increased in aged female rats in diestrus, but not in estrus. Taken together, these data suggest that in males, but not females, normal aging may result in decreased serotonergic facilitation of Hypoglossal motoneurons that could result in reduced airway patency.
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age related changes in serotonin in the Hypoglossal Nucleus of rat implications for sleep disordered breathing
Neuroscience Letters, 1999Co-Authors: Mary Behan, Mark S BrownfieldAbstract:We are attempting to determine the neuronal factors that influence upper airway patency during sleep in the elderly. Serotonin has a facilitatory effect on Hypoglossal motoneurons that innervate the tongue, and manipulations of the serotonergic system alter airway patency. We hypothesized that age-associated changes in serotonergic input to the Hypoglossal Nucleus might be a factor in the increased susceptibility to sleep-disordered breathing in the elderly. We used light microscopic immunocytochemistry to study the distribution of serotonin in the Hypoglossal Nucleus in young and old rats. Rats > 18 months had fewer serotonin immunoreactive axons and boutons in the Hypoglossal Nucleus than rats < 6 months. These data suggest that normal aging may result in a change in the availability of serotonin that results in decreased facilitation of Hypoglossal motoneurons.
Scott Manaker - One of the best experts on this subject based on the ideXlab platform.
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colocalization of substance p or enkephalin in serotonergic neuronal afferents to the Hypoglossal Nucleus in the rat
The Journal of Comparative Neurology, 1998Co-Authors: John N Henry, Scott ManakerAbstract:The serotonergic innervation of the Hypoglossal Nucleus originates from the caudal raphe nuclei. Non-serotonergic neurons in the caudal raphe nuclei also project to the Hypoglossal Nucleus. We employed a triple-fluorescence technique to determine whether the substance P- or the enkephalin-containing neurons in the caudal raphe nuclei that projected to the Hypoglossal Nucleus also contained serotonin. Rhodamine latex microspheres were injected into the Hypoglossal Nucleus, and then serotonin and peptide dual-immunofluorescence was performed to colocalize perikarya containing serotonin, substance P, and rhodamine microspheres; or perikarya containing serotonin, enkephalin, and rhodamine microspheres. Our results demonstrate that most substance P-containing neuronal afferents to the Hypoglossal Nucleus colocalize serotonin. In contrast, few enkephalin-containing neuronal afferents to the Hypoglossal Nucleus also contain serotonin. These data suggest that substance P projections to the Hypoglossal Nucleus are a subset of serotonergic projections and that limited overlap exists between the populations of enkephalinergic and serotonergic neuronal afferents to the Hypoglossal Nucleus. Either substance P- or enkephalin-containing somata account for a very small proportion of non-serotonergic caudal raphe projections to the Hypoglossal Nucleus. Finally, these data demonstrate the medial tegmental field origins of the substance P projections and the enkephalin projections to the Hypoglossal Nucleus.
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origin of serotoninergic afferents to the Hypoglossal Nucleus in the rat
The Journal of Comparative Neurology, 1993Co-Authors: Scott Manaker, Laura J TischlerAbstract:The Hypoglossal Nucleus contains serotonin and several different serotonin receptors, and serotonin is present in fibers and terminals contacting Hypoglossal motoneurons. Serotonin alters the excitability of Hypoglossal motoneurons, and may influence Hypoglossal motoneuron activity in a variety of physiological processes. Since the Hypoglossal Nucleus contains no serotoninergic somata, the present study sought to identify the sources of serotoninergic afferents to the Hypoglossal Nucleus. Fluorogold was injected into the Hypoglossal Nucleus and serotoninergic immunofluorescence was utilized in a dual-fluorescence technique to identify the sources of serotoninergic afferents to the Hypoglossal Nucleus. The results demonstrate that most serotoninergic afferents to the Hypoglossal Nucleus originate from the nuclei raphe pallidus and obscurus, while fewer originate from the Nucleus raphe magnus and the parapyramidal region. Other regions of the medial tegmental field and the pons that contain both serotoninergic neurons and neuronal afferents to the Hypoglossal Nucleus contain no double-labeled neurons.
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raphespinal and reticulospinal axon collaterals to the Hypoglossal Nucleus in the rat
The Journal of Comparative Neurology, 1992Co-Authors: Scott Manaker, Laura J Tischler, Adrian R MorrisonAbstract:Neurons in the medial tegmental field project directly to spinal somatic motoneurons and to cranial motoneuron pools such as the Hypoglossal Nucleus. The axons of these neurons may be highly collateralized, projecting to multiple levels of the spinal cord and to many diverse regions at different levels of the neuraxis. We employed a double fluorescent retrograde tracer technique to examine whether medial tegmental neurons that project to the spinal cord also project to the Hypoglossal Nucleus. Injections of Diamidino Yellow into the Hypoglossal Nucleus and Fast Blue into the spinal cord produced large numbers of double labeled neurons in the medial tegmental field, particularly in the caudal raphe nuclei and adjacent ventromedial reticular formation. In these structures the number of neurons projecting to both the Hypoglossal Nucleus and the spinal cord was equivalent to the number of neurons projecting to multiple levels of the spinal cord observed in control animals. Fewer neurons projecting to both the Hypoglossal Nucleus and the spinal cord were observed in several other nuclei and subregions of the medial tegmental field, while almost no such neurons were observed in the lateral tegmental field or other pontomedullary structures. These results demonstrate that neurons of the caudal raphe nuclei and adjacent ventromedial reticular formation project to both the spinal cord and the Hypoglossal Nucleus, and support the concept that the diffuse projections to motoneuron pools from the medial tegmental field globally modulate both spinal and cranial somatic motoneuron excitability.
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neurons of the motor trigeminal Nucleus project to the Hypoglossal Nucleus in the rat
Experimental Brain Research, 1992Co-Authors: Scott Manaker, Laura J Tischler, Tracey L Bigler, Adrian R MorrisonAbstract:The Hypoglossal Nucleus (Mo12) contains motoneurons that innervate the tongue, while the motor trigeminal Nucleus (Mo5) contains motoneurons that elevate or depress the mandible. Previous studies have revealed lateral and medial tegmental field neuronal afferents to the Mo12 adjacent to, but not within, the motor trigeminal Nucleus (Mo5). The current studies demonstrate the presence of retrogradely labeled neuronal afferents to the Mo12 within the Mo5 produced by as little as 10 nl of Fast Blue (FB) injected into the Mo12. Retrograde labeling of Mo5 afferents to the Mo12 with injections of Diamidino Yellow (DY) combined with injections of FB into the lumbar spinal cord showed these neuronal afferents to the Mo12 are not part of the diffuse projections to motoneurons from the Nucleus subcoeruleus. Retrograde labeling of Mo5 afferents to the Mo12 with DY combined with injections of FB into the masseter revealed these neuronal afferents to the Mo12 are not trigeminal motoneurons. These results indicate that Mo5 interneurons are part of the lateral tegmental field projections to the Mo12, and are likely to comprise part of the neural substrate coordinating the motor activity of the jaw and tongue.