The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Yoshitaka Oka - One of the best experts on this subject based on the ideXlab platform.
-
juvenile specific burst firing of Terminal Nerve gnrh3 neurons suggests novel functions in addition to neuromodulation
Endocrinology, 2018Co-Authors: Chie Umatani, Yoshitaka OkaAbstract:Peptidergic neurons are suggested to play a key role in neuromodulation of animal behaviors in response to sensory cues in the environment. Terminal Nerve gonadotropin-releasing hormone 3 (TN-GnRH3) neurons are thought to be one of the peptidergic neurons important for such neuromodulation in adult vertebrates. On the other hand, it has been reported that TN-GnRH3 neurons are labeled by a specific GnRH3 antibody from early developmental stages to adulthood and are thus suggested to produce mature GnRH3 peptide even in the early developmental stages. However, it remains unknown when TN-GnRH3 neurons show spontaneous burst firing, which is suggested to be involved in neuropeptide release. Using a whole-brain in vitro preparation of gnrh3:enhanced green fluorescent protein (EGFP) medaka fish, we first recorded spontaneous firings of TN-GnRH3 neurons after hatching to adulthood. Contrary to what one would expect from their neuromodulatory functions-that TN-GnRH3 neurons are more active in adulthood-TN-GnRH3 neurons in juveniles showed spontaneous burst firing more frequently than in adulthood (juvenile-specific burst firing). Ca2+ imaging of TN-GnRH3 neurons in juveniles may further suggest that juvenile-specific burst firing triggers neuropeptide release. Furthermore, juvenile-specific burst firing was suggested to be induced by blocking persistent GABAergic inhibition to the glutamatergic neurons, which leads to an increase in glutamatergic synaptic inputs to TN-GnRH3 neurons. The present study reports that peptidergic neurons show juvenile-specific burst firing involved in triggering peptide release and suggests that juvenile TN-GnRH3 neurons have novel functions, in addition to neuromodulation.
-
burst generation mediated by cholinergic input in Terminal Nerve gonadotrophin releasing hormone neurones of the goldfish
The Journal of Physiology, 2013Co-Authors: Takafumi Kawai, Hideki Abe, Yoshitaka OkaAbstract:Key points • Burst firing activities are effective for the release of neuropeptides from peptidergic neurones. • A peptidergic neurone, the Terminal Nerve (TN)-gonadotrophin releasing hormone (GnRH) neurone, shows spontaneous burst firing activities only infrequently. • Only a single pulse electrical stimulation of the neuropil surrounding the TN-GnRH neurones induces transient burst activities in TN-GnRH neurones via cholinergic mechanisms. • The activation of muscarinic acetylcholine receptors results in a long-lasting hyperpolarisation, inducing rebound burst activities in TN-GnRH neurones. • These new findings suggest a novel type of cholinergic regulation of burst activities in peptidergic neurones, which should contribute to the release of neuropeptides. Abstract Peptidergic neurones play a pivotal role in the neuromodulation of widespread areas in the nervous system. Generally, it has been accepted that the peptide release from these neurones is regulated by their firing activities. The Terminal Nerve (TN)-gonadotrophin releasing hormone (GnRH) neurones, which are one of the well-studied peptidergic neurones in vertebrate brains, are characterised by their spontaneous regular pacemaker activities, and GnRH has been suggested to modulate the sensory responsiveness of animals. Although many peptidergic neurones are known to exhibit burst firing activities when they release the peptides, TN-GnRH neurones show spontaneous burst firing activities only infrequently. Thus, it remains to be elucidated whether the TN-GnRH neurones show burst activities and, if so, how the mode switching between the regular pacemaking and bursting modes is regulated in these neurones. In this study, we found that only a single pulse electrical stimulation of the neuropil surrounding the TN-GnRH neurones reproducibly induces transient burst activities in TN-GnRH neurones. Our combined physiological and morphological data suggest that this phenomenon occurs following slow inhibitory postsynaptic potentials mediated by cholinergic Terminals surrounding the TN-GnRH neurones. We also found that the activation of muscarinic acetylcholine receptors induces persistent opening of potassium channels, resulting in a long-lasting hyperpolarisation. This long hyperpolarisation induces sustained rebound depolarisation that has been suggested to be generated by a combination of persistent voltage-gated Na+ channels and low-voltage-activated Ca2+ channels. These new findings suggest a novel type of cholinergic regulation of burst activities in peptidergic neurones, which should contribute to the release of neuropeptides.
-
neuropeptide rfrp inhibits the pacemaker activity of Terminal Nerve gnrh neurons
Journal of Neurophysiology, 2013Co-Authors: Chie Umatani, Hideki Abe, Yoshitaka OkaAbstract:The Terminal Nerve gonadotropin-releasing hormone (TN-GnRH) neurons show spontaneous pacemaker activity whose firing frequency is suggested to regulate the release of GnRH peptides and control moti...
-
expression of vesicular glutamate transporter 2 1 in medaka Terminal Nerve gonadotrophin releasing hormone neurones
Journal of Neuroendocrinology, 2011Co-Authors: Yasuhisa Akazome, Shinji Kanda, Yoshitaka OkaAbstract:There are three paralogous genes for gonadotrophin-releasing hormone (GnRH) peptides of vertebrates in general. GnRH1, the protein product of gnrh1 gene, is the hypophysiotrophic neuropeptide, and is a critical regulator of gonadotrophin secretion, whereas GnRH2 and GnRH3 are regarded to have neuromodulatory functions. In some teleost species, the Terminal Nerve (TN) GnRH3 neuronal system, which expresses GnRH3, has been shown to project extensively throughout the brain and regulate the motivational state for some behavioural repertoires. In recent years, it has been considered that most, if not all, peptidergic and aminergic neurones synthesise and release more than one neurotransmitter, and the cotransmission of conventional small-molecule neurotransmitters, such as GABA, glutamate or acetylcholine together with neuropeptides, is regarded as a common feature of such neurones. For a functional characterisation of the GnRH3 neuronal system, we examined the possible co-expression of conventional neurotransmitters, GABA, acetylcholine and glutamate, in addition to GnRH in the TN-GnRH3 neurone by reverse transcriptase-polymerase chain reaction (RT-PCR) and in situ hybridisation of recently identified marker genes for neurotransmitters using a teleost fish medaka (Oryzias latipes). By RT-PCR and dual-label in situ hybridisation, we demonstrated the co-expression of GnRH3 and vesicular transporter for glutamate (VGluT) 2.1. in a single TN-GnRH3 neurone. We therefore suggest that the TN-GnRH3 neurones use glutamate as a cotransmitter of GnRH.
-
the role of the Terminal Nerve and gnrh in olfactory system neuromodulation
Zoological Science, 2009Co-Authors: Takafumi Kawai, Yoshitaka Oka, Heather L EisthenAbstract:Animals must regulate their sensory responsiveness appropriately with respect to their internal and external environments, which is accomplished in part via centrifugal modulatory pathways. In the olfactory sensory system, responsiveness is regulated by neuromodulators released from centrifugal fibers into the olfactory epithelium and bulb. Among the modulators known to modulate neural activity of the olfactory system, one of the best understood is gonadotropin-releasing hormone (GnRH). This is because GnRH derives mainly from the Terminal Nerve (TN), and the TN-GnRH system has been suggested to function as a neuromodulator in wide areas of the brain, including the olfactory bulb. In the present article we examine the modulatory roles of the TN and GnRH in the olfactory epithelium and bulb as a model for understanding the ways in which olfactory responses can be tuned to the internal and external environments.
Nancy L. Wayne - One of the best experts on this subject based on the ideXlab platform.
-
Actions of Bisphenol A and Bisphenol S on the Reproductive Neuroendocrine System During Early Development in Zebrafish
Endocrinology, 2015Co-Authors: Wenhui Qiu, Yali Zhao, Ming Yang, Matthew Farajzadeh, Chenyuan Pan, Nancy L. WayneAbstract:Bisphenol A (BPA) is a well-known environmental, endocrine-disrupting chemical, and bisphenol S (BPS) has been considered a safer alternative for BPA-free products. The present study aims to evaluate the impact of BPA and BPS on the reproductive neuroendocrine system during zebrafish embryonic and larval development and to explore potential mechanisms of action associated with estrogen receptor (ER), thyroid hormone receptor (THR), and enzyme aromatase (AROM) pathways. Environmentally relevant, low levels of BPA exposure during development led to advanced hatching time, increased numbers of GnRH3 neurons in both Terminal Nerve and hypothalamus, increased expression of reproduction-related genes (kiss1, kiss1r, gnrh3, lhβ, fshβ, and erα), and a marker for synaptic transmission (sv2). Low levels of BPS exposure led to similar effects: increased numbers of hypothalamic GnRH3 neurons and increased expression of kiss1, gnrh3, and erα. Antagonists of ER, THRs, and AROM blocked many of the effects of BPA and BPS on reproduction-related gene expression, providing evidence that those three pathways mediate the actions of BPA and BPS on the reproductive neuroendocrine system. This study demonstrates that alternatives to BPA used in the manufacture of BPA-free products are not necessarily safer. Furthermore, this is the first study to describe the impact of low-level BPA and BPS exposure on the Kiss/Kiss receptor system during development. It is also the first report of multiple cellular pathways (ERα, THRs, and AROM) mediating the effects of BPA and BPS during embryonic development in any species.
-
effects of kisspeptin1 on electrical activity of an extrahypothalamic population of gonadotropin releasing hormone neurons in medaka oryzias latipes
PLOS ONE, 2012Co-Authors: Yali Zhao, Nancy L. WayneAbstract:Kisspeptin (product of the kiss1 gene) is the most potent known activator of the hypothalamo-pituitary-gonadal axis. Both kiss1 and the kisspeptin receptor are highly expressed in the hypothalamus of vertebrates, and low doses of kisspeptin have a robust and long-lasting stimulatory effect on the rate of action potential firing of hypophysiotropic gonadotropin releasing hormone-1 (GnRH1) neurons in mice. Fish have multiple populations of GnRH neurons distinguished by their location in the brain and the GnRH gene that they express. GnRH3 neurons located in the Terminal Nerve (TN) associated with the olfactory bulb are neuromodulatory and do not play a direct role in regulating pituitary-gonadal function. In medaka fish, the electrical activity of TN-GnRH3 neurons is modulated by visual cues from conspecifics, and is thought to act as a transmitter of information from the external environment to the central nervous system. TN-GnRH3 neurons also play a role in sexual motivation and arousal states, making them an important population of neurons to study for understanding coordination of complex behaviors. We investigated the role of kisspeptin in regulating electrical activity of TN-GnRH3 neurons in adult medaka. Using electrophysiology in an intact brain preparation, we show that a relatively brief treatment with 100 nM of kisspeptin had a long-lasting stimulatory effect on the electrical activity of an extrahypothalamic population of GnRH neurons. Dose-response analysis suggests a relatively narrow activational range of this neuropeptide. Further, blocking action potential firing with tetrodotoxin and blocking synaptic transmission with a low Ca(2+)/high Mg(2+) solution inhibited the stimulatory action of kisspeptin on electrical activity, indicating that kisspeptin is acting indirectly through synaptic regulation to excite TN-GnRH3 neurons. Our findings provide a new perspective on kisspeptin's broader functions within the central nervous system, through its regulation of an extrahypothalamic population of GnRH neurons involved in multiple neuromodulatory functions.
-
acquisition of spontaneous electrical activity during embryonic development of gonadotropin releasing hormone 3 neurons located in the Terminal Nerve of transgenic zebrafish danio rerio
General and Comparative Endocrinology, 2010Co-Authors: Siddharth Ramakrishnan, Wenjau Lee, Sammy Navarre, David J Kozlowski, Nancy L. WayneAbstract:There are multiple populations of gonadotropin releasing hormone (GnRH) neurons that have distinct physiological and behavioral functions. Teleost fish have a population of GnRH3 neurons located in the Terminal Nerve (TN) associated with the olfactory bulb that is thought to play a neuromodulatory role in multiple physiological systems, including olfactory, visual, and reproductive. We used transgenic zebrafish in which the GnRH3 promoter drives expression of a green fluorescent protein to identify GnRH3 neurons during development in live embryos. Unlike with hypophysiotropic GnRH neurons of zebrafish, TN-GnRH3 neurons are of neural crest origin and are one of the first populations of GnRH neurons to develop in the early embryo. Using a combination of optical imaging and electrophysiology, we showed that during the first three days post-fertilization, TN-GnRH3 neurons increase in number, extend neural projections, move in association with tissue expansion, and acquire an adult-pattern of spontaneous action potential firing. Early during development, about half of the neurons were quiescent/non-firing. Later, at three days post-fertilization, there was an increase in the proportion of neurons showing action potential firing and an increase in the number of neurons that showed an adult-like tonic or beating pattern of action potential firing with a firing frequency similar to that seen in adult TN-GnRH3 neurons. This study represents the first neurophysiological investigation of developing GnRH neurons in live embryos -- an important advance in understanding their potential non-reproductive roles during embryogenesis.
-
social cues from conspecifics alter electrical activity of gonadotropin releasing hormone neurons in the Terminal Nerve via visual signals
American Journal of Physiology-regulatory Integrative and Comparative Physiology, 2009Co-Authors: Siddharth Ramakrishnan, Nancy L. WayneAbstract:There are multiple populations of gonadotropin-releasing hormone (GnRH) neurons in the brains of vertebrates. The population located in the hypothalamus/preoptic area is the best studied and is kno...
-
whole cell electrophysiology of gonadotropin releasing hormone neurons that express green fluorescent protein in the Terminal Nerve of transgenic medaka oryzias latipes
Biology of Reproduction, 2005Co-Authors: Nancy L. Wayne, Kenrick Kuwahara, Katsumi Aida, Yoshitaka Nagahama, Kataaki OkuboAbstract:Gonadotropin-releasing hormone (GnRH) controls reproduction in vertebrates. Most studies have focused on the population of GnRH neurons in the hypothalamus that ultimately controls gonadal function. However, all vertebrates studied to date have two to three anatomically distinct populations of GnRH neurons that express different forms of this hormone. The purpose of the present study was to develop a new model for studying the population of GnRH neurons in the Terminal Nerve (TN) associated with the olfactory bulb and then to characterize their pattern of action potential firing to provide a foundation for understanding the role of these neurons in regulating reproduction. A stable line of transgenic medaka (Oryzias latipes) was generated in which a DNA construct containing the salmon GnRH (Gnrh3) promoter linked to green fluorescent protein (GFP) was expressed in TN-GnRH3 neurons. This population of GnRH neurons is located at or near the ventral surface of the brain, making them ideally situated for electrophysiological analysis. Whole-cell and loose-patch recordings in current-clamp mode were performed on these neurons from excised, intact brains of adult males in which afferent and efferent neural connections remained intact. All TN-GnRH3GFP neurons that we recorded showed a beating pattern of spontaneous action potential firing. Action potentials were blocked by tetrodotoxin, indicating they are generated by a voltage-sensitive Na þ current; however, an oscillation in subthreshold membrane potential persisted. The present results indicate that this transgenic fish will provide an excellent model for studying the cell physiology of an extrahypothalamic population of GnRH neurons.
William E Bemis - One of the best experts on this subject based on the ideXlab platform.
-
cranial Nerves of the coelacanth latimeria chalumnae osteichthyes sarcopterygii actinistia and comparisons with other craniata
Brain Behavior and Evolution, 1993Co-Authors: R. Glenn Northcutt, William E BemisAbstract:: We reconstructed the cranial Nerves of a serially sectioned prenatal coelacanth, Latimeria chalumnae. This allowed us to correct several mistakes in the literature and to make broad phylogenetic comparisons with other craniates. The genera surveyed in our phylogenetic analysis were Eptatretus, Myxine, Petromyzon, Lampetra, Chimaera, Hydrolagus, Squalus, Mustelus, Polypterus, Acipenser, Lepisosteus, Amia, Neoceratodus, Protopterus, Lepidosiren, Latimeria and Ambystoma. Cladistic analysis of our data shows that Latimeria shares with Ambystoma two characters of the cranial Nerves. Our chief findings are: 1) Latimeria possesses an external nasal papilla and pedunculated olfactory bulbs but lacks a discrete Terminal Nerve. In other respects its olfactory system resembles the plesiomorphic pattern for craniates. 2) The optic Nerve is plicated, a character found in many but not all gnathostomes. Latimeria retains an interdigitated partial decussation of the optic Nerves, a character found in all craniates surveyed. 3) The oculomotor Nerve supplies the same extrinsic eye muscles as in lampreys and gnathostomes. As in gnathostomes generally, Latimeria has a ciliary ganglion but its cells are located intracranially in the root of the oculomotor Nerve, and their processes reach the eye via oculomotor and profundal rami. 4) The trochlear Nerve supplies the superior oblique muscle as in all craniates that have not secondarily reduced the eye and its extrinsic musculature. 5) The profundal ganglion and ramus are entirely separate from the trigeminal system, with no exchange of fibers. This character has an interesting phylogenetic distribution: in hagfishes, lampreys, lungfishes and tetrapods, the profundal and trigeminal ganglia are fused, whereas in other taxa surveyed the ganglia are separate. The principal tissues innervated by the profundal Nerve are the membranous walls of the tubes of the rostral organ. 6) As in lampreys and gnathostomes, the trigeminal Nerve has maxillary and mandibular rami. Unlike all other gnathostomes surveyed, the trigeminal Nerve of Latimeria lacks a sizable superficial ophthalmic ramus. Thus, Latimeria lacks the well-developed superficial ophthalmic complex reported in most other fishes. As in gnathostomes generally, the maxillary ramus of the trigeminal Nerve fuses with the buccal ramus of the anterodorsal lateral line Nerve to form the buccal+maxillary complex. We reject the term 'Gasserian ganglion', which is often applied to the fused profundal and trigeminal ganglion of tetrapods. 7) The abducent Nerve innervates not only the lateral rectus muscle (a character common to myopterygians) but also the basicranial muscle. As we previously reported, it is probable that the basicranial muscle of Latimeria is homologous to the ocular retracter muscle of amphibians.(ABSTRACT TRUNCATED AT 400 WORDS)
-
cranial Nerves of the coelacanth latimeria chalumnae osteichthyes sarcopterygii actinistia and comparisons with other craniata
Brain Behavior and Evolution, 1993Co-Authors: R. Glenn Northcutt, William E BemisAbstract:: We reconstructed the cranial Nerves of a serially sectioned prenatal coelacanth, Latimeria chalumnae. This allowed us to correct several mistakes in the literature and to make broad phylogenetic comparisons with other craniates. The genera surveyed in our phylogenetic analysis were Eptatretus, Myxine, Petromyzon, Lampetra, Chimaera, Hydrolagus, Squalus, Mustelus, Polypterus, Acipenser, Lepisosteus, Amia, Neoceratodus, Protopterus, Lepidosiren, Latimeria and Ambystoma. Cladistic analysis of our data shows that Latimeria shares with Ambystoma two characters of the cranial Nerves. Our chief findings are: 1) Latimeria possesses an external nasal papilla and pedunculated olfactory bulbs but lacks a discrete Terminal Nerve. In other respects its olfactory system resembles the plesiomorphic pattern for craniates. 2) The optic Nerve is plicated, a character found in many but not all gnathostomes. Latimeria retains an interdigitated partial decussation of the optic Nerves, a character found in all craniates surveyed. 3) The oculomotor Nerve supplies the same extrinsic eye muscles as in lampreys and gnathostomes. As in gnathostomes generally, Latimeria has a ciliary ganglion but its cells are located intracranially in the root of the oculomotor Nerve, and their processes reach the eye via oculomotor and profundal rami. 4) The trochlear Nerve supplies the superior oblique muscle as in all craniates that have not secondarily reduced the eye and its extrinsic musculature. 5) The profundal ganglion and ramus are entirely separate from the trigeminal system, with no exchange of fibers. This character has an interesting phylogenetic distribution: in hagfishes, lampreys, lungfishes and tetrapods, the profundal and trigeminal ganglia are fused, whereas in other taxa surveyed the ganglia are separate. The principal tissues innervated by the profundal Nerve are the membranous walls of the tubes of the rostral organ. 6) As in lampreys and gnathostomes, the trigeminal Nerve has maxillary and mandibular rami. Unlike all other gnathostomes surveyed, the trigeminal Nerve of Latimeria lacks a sizable superficial ophthalmic ramus. Thus, Latimeria lacks the well-developed superficial ophthalmic complex reported in most other fishes. As in gnathostomes generally, the maxillary ramus of the trigeminal Nerve fuses with the buccal ramus of the anterodorsal lateral line Nerve to form the buccal+maxillary complex. We reject the term 'Gasserian ganglion', which is often applied to the fused profundal and trigeminal ganglion of tetrapods. 7) The abducent Nerve innervates not only the lateral rectus muscle (a character common to myopterygians) but also the basicranial muscle. As we previously reported, it is probable that the basicranial muscle of Latimeria is homologous to the ocular retracter muscle of amphibians.(ABSTRACT TRUNCATED AT 400 WORDS)
R. Glenn Northcutt - One of the best experts on this subject based on the ideXlab platform.
-
cranial Nerves of the coelacanth latimeria chalumnae osteichthyes sarcopterygii actinistia and comparisons with other craniata
Brain Behavior and Evolution, 1993Co-Authors: R. Glenn Northcutt, William E BemisAbstract:: We reconstructed the cranial Nerves of a serially sectioned prenatal coelacanth, Latimeria chalumnae. This allowed us to correct several mistakes in the literature and to make broad phylogenetic comparisons with other craniates. The genera surveyed in our phylogenetic analysis were Eptatretus, Myxine, Petromyzon, Lampetra, Chimaera, Hydrolagus, Squalus, Mustelus, Polypterus, Acipenser, Lepisosteus, Amia, Neoceratodus, Protopterus, Lepidosiren, Latimeria and Ambystoma. Cladistic analysis of our data shows that Latimeria shares with Ambystoma two characters of the cranial Nerves. Our chief findings are: 1) Latimeria possesses an external nasal papilla and pedunculated olfactory bulbs but lacks a discrete Terminal Nerve. In other respects its olfactory system resembles the plesiomorphic pattern for craniates. 2) The optic Nerve is plicated, a character found in many but not all gnathostomes. Latimeria retains an interdigitated partial decussation of the optic Nerves, a character found in all craniates surveyed. 3) The oculomotor Nerve supplies the same extrinsic eye muscles as in lampreys and gnathostomes. As in gnathostomes generally, Latimeria has a ciliary ganglion but its cells are located intracranially in the root of the oculomotor Nerve, and their processes reach the eye via oculomotor and profundal rami. 4) The trochlear Nerve supplies the superior oblique muscle as in all craniates that have not secondarily reduced the eye and its extrinsic musculature. 5) The profundal ganglion and ramus are entirely separate from the trigeminal system, with no exchange of fibers. This character has an interesting phylogenetic distribution: in hagfishes, lampreys, lungfishes and tetrapods, the profundal and trigeminal ganglia are fused, whereas in other taxa surveyed the ganglia are separate. The principal tissues innervated by the profundal Nerve are the membranous walls of the tubes of the rostral organ. 6) As in lampreys and gnathostomes, the trigeminal Nerve has maxillary and mandibular rami. Unlike all other gnathostomes surveyed, the trigeminal Nerve of Latimeria lacks a sizable superficial ophthalmic ramus. Thus, Latimeria lacks the well-developed superficial ophthalmic complex reported in most other fishes. As in gnathostomes generally, the maxillary ramus of the trigeminal Nerve fuses with the buccal ramus of the anterodorsal lateral line Nerve to form the buccal+maxillary complex. We reject the term 'Gasserian ganglion', which is often applied to the fused profundal and trigeminal ganglion of tetrapods. 7) The abducent Nerve innervates not only the lateral rectus muscle (a character common to myopterygians) but also the basicranial muscle. As we previously reported, it is probable that the basicranial muscle of Latimeria is homologous to the ocular retracter muscle of amphibians.(ABSTRACT TRUNCATED AT 400 WORDS)
-
cranial Nerves of the coelacanth latimeria chalumnae osteichthyes sarcopterygii actinistia and comparisons with other craniata
Brain Behavior and Evolution, 1993Co-Authors: R. Glenn Northcutt, William E BemisAbstract:: We reconstructed the cranial Nerves of a serially sectioned prenatal coelacanth, Latimeria chalumnae. This allowed us to correct several mistakes in the literature and to make broad phylogenetic comparisons with other craniates. The genera surveyed in our phylogenetic analysis were Eptatretus, Myxine, Petromyzon, Lampetra, Chimaera, Hydrolagus, Squalus, Mustelus, Polypterus, Acipenser, Lepisosteus, Amia, Neoceratodus, Protopterus, Lepidosiren, Latimeria and Ambystoma. Cladistic analysis of our data shows that Latimeria shares with Ambystoma two characters of the cranial Nerves. Our chief findings are: 1) Latimeria possesses an external nasal papilla and pedunculated olfactory bulbs but lacks a discrete Terminal Nerve. In other respects its olfactory system resembles the plesiomorphic pattern for craniates. 2) The optic Nerve is plicated, a character found in many but not all gnathostomes. Latimeria retains an interdigitated partial decussation of the optic Nerves, a character found in all craniates surveyed. 3) The oculomotor Nerve supplies the same extrinsic eye muscles as in lampreys and gnathostomes. As in gnathostomes generally, Latimeria has a ciliary ganglion but its cells are located intracranially in the root of the oculomotor Nerve, and their processes reach the eye via oculomotor and profundal rami. 4) The trochlear Nerve supplies the superior oblique muscle as in all craniates that have not secondarily reduced the eye and its extrinsic musculature. 5) The profundal ganglion and ramus are entirely separate from the trigeminal system, with no exchange of fibers. This character has an interesting phylogenetic distribution: in hagfishes, lampreys, lungfishes and tetrapods, the profundal and trigeminal ganglia are fused, whereas in other taxa surveyed the ganglia are separate. The principal tissues innervated by the profundal Nerve are the membranous walls of the tubes of the rostral organ. 6) As in lampreys and gnathostomes, the trigeminal Nerve has maxillary and mandibular rami. Unlike all other gnathostomes surveyed, the trigeminal Nerve of Latimeria lacks a sizable superficial ophthalmic ramus. Thus, Latimeria lacks the well-developed superficial ophthalmic complex reported in most other fishes. As in gnathostomes generally, the maxillary ramus of the trigeminal Nerve fuses with the buccal ramus of the anterodorsal lateral line Nerve to form the buccal+maxillary complex. We reject the term 'Gasserian ganglion', which is often applied to the fused profundal and trigeminal ganglion of tetrapods. 7) The abducent Nerve innervates not only the lateral rectus muscle (a character common to myopterygians) but also the basicranial muscle. As we previously reported, it is probable that the basicranial muscle of Latimeria is homologous to the ocular retracter muscle of amphibians.(ABSTRACT TRUNCATED AT 400 WORDS)
Hideki Abe - One of the best experts on this subject based on the ideXlab platform.
-
burst generation mediated by cholinergic input in Terminal Nerve gonadotrophin releasing hormone neurones of the goldfish
The Journal of Physiology, 2013Co-Authors: Takafumi Kawai, Hideki Abe, Yoshitaka OkaAbstract:Key points • Burst firing activities are effective for the release of neuropeptides from peptidergic neurones. • A peptidergic neurone, the Terminal Nerve (TN)-gonadotrophin releasing hormone (GnRH) neurone, shows spontaneous burst firing activities only infrequently. • Only a single pulse electrical stimulation of the neuropil surrounding the TN-GnRH neurones induces transient burst activities in TN-GnRH neurones via cholinergic mechanisms. • The activation of muscarinic acetylcholine receptors results in a long-lasting hyperpolarisation, inducing rebound burst activities in TN-GnRH neurones. • These new findings suggest a novel type of cholinergic regulation of burst activities in peptidergic neurones, which should contribute to the release of neuropeptides. Abstract Peptidergic neurones play a pivotal role in the neuromodulation of widespread areas in the nervous system. Generally, it has been accepted that the peptide release from these neurones is regulated by their firing activities. The Terminal Nerve (TN)-gonadotrophin releasing hormone (GnRH) neurones, which are one of the well-studied peptidergic neurones in vertebrate brains, are characterised by their spontaneous regular pacemaker activities, and GnRH has been suggested to modulate the sensory responsiveness of animals. Although many peptidergic neurones are known to exhibit burst firing activities when they release the peptides, TN-GnRH neurones show spontaneous burst firing activities only infrequently. Thus, it remains to be elucidated whether the TN-GnRH neurones show burst activities and, if so, how the mode switching between the regular pacemaking and bursting modes is regulated in these neurones. In this study, we found that only a single pulse electrical stimulation of the neuropil surrounding the TN-GnRH neurones reproducibly induces transient burst activities in TN-GnRH neurones. Our combined physiological and morphological data suggest that this phenomenon occurs following slow inhibitory postsynaptic potentials mediated by cholinergic Terminals surrounding the TN-GnRH neurones. We also found that the activation of muscarinic acetylcholine receptors induces persistent opening of potassium channels, resulting in a long-lasting hyperpolarisation. This long hyperpolarisation induces sustained rebound depolarisation that has been suggested to be generated by a combination of persistent voltage-gated Na+ channels and low-voltage-activated Ca2+ channels. These new findings suggest a novel type of cholinergic regulation of burst activities in peptidergic neurones, which should contribute to the release of neuropeptides.
-
neuropeptide rfrp inhibits the pacemaker activity of Terminal Nerve gnrh neurons
Journal of Neurophysiology, 2013Co-Authors: Chie Umatani, Hideki Abe, Yoshitaka OkaAbstract:The Terminal Nerve gonadotropin-releasing hormone (TN-GnRH) neurons show spontaneous pacemaker activity whose firing frequency is suggested to regulate the release of GnRH peptides and control moti...
