摘要:

This study describes the discharges of central units in the medulla of the goldfish, Carassius auratus, to hydrodynamic stimuli received by the lateral line. We stimulated the animal with a small object moving in the water and recorded activity of 85 medullary lateral line units in response to different motion directions and to various object distances, velocities, accelerations and sizes. All but one unit increased discharge rate when the moving object passed the fish laterally. Five response types were distinguished based on temporal patterns of unit responses. Ten units were recorded which encoded motion direction by different temporal discharge patterns. In general, discharge rates decreased when object distance was increased and when object speed was decreased. When object size was decreased, discharge rates decreased systematically in one group of units, but they were comparable for all but the smallest object tested in a second group of units. Units responded about equally well whether an object was moved at a constant velocity or was accelerated when it passed the fish. The data indicate that medullary lateral line units in the goldfish can encode motion direction but are not tuned to other aspects of an object moving in the water. The functional properties of units in the medulla of goldfish are similar to those reported for medullary units in the catfish Ancistrus sp., suggesting that the central mechanisms for processing complex hydrodynamic stimuli may be quite similar in fish species that occupy habitats with different hydrodynamic conditions.

ISSN:0006-8977    

DOI:10.1159/000113341

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

This study describes the discharges of central units in the medulla of the goldfish, Carassius auratus, to hydrodynamic stimuli received by the lateral line. We stimulated the animal with a small object moving in the water and recorded activity of 85 medullary lateral line units in response to different motion directions and to various object distances, velocities, accelerations and sizes. All but one unit increased discharge rate when the moving object passed the fish laterally. Five response types were distinguished based on temporal patterns of unit responses. Ten units were recorded which encoded motion direction by different temporal discharge patterns. In general, discharge rates decreased when object distance was increased and when object speed was decreased. When object size was decreased, discharge rates decreased systematically in one group of units, but they were comparable for all but the smallest object tested in a second group of units. Units responded about equally well whether an object was moved at a constant velocity or was accelerated when it passed the fish. The data indicate that medullary lateral line units in the goldfish can encode motion direction but are not tuned to other aspects of an object moving in the water. The functional properties of units in the medulla of goldfish are similar to those reported for medullary units in the catfish Ancistrus sp., suggesting that the central mechanisms for processing complex hydrodynamic stimuli may be quite similar in fish species that occupy habitats with different hydrodynamic conditions.

ISSN:0006-8977    

DOI:10.1159/000316298

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

This study examined the distribution of the neuropeptides somatostatin (SS) and calcitonin gene-related peptide (CGRP) in forebrain and midbrain song-control nuclei of male versus female brains in adult zebra finches (Poephila guttata) using immunohistochemical techniques. Vocal learning in songbirds is controlled by an interconnected, highly-localized system of brain nuclei. Male zebra finches produce learned vocalizations, and females do not. This behavioral sexual dimorphism is reflected in a substantial difference in the size of these song-control nuclei: males have larger nuclei containing a greater number of neurons than do females. Interestingly, previous studies describing neurochemical aspects of the song-control system in other songbird species have not reported any obvious sex differences. However, the results of this study showed that the level of neuropeptide staining was substantially greater in telencephalic song-control nuclei of male brains compared to female brains in zebra finches. In some brain regions females lacked any apparent staining, whereas male brains were intensely labeled. In other cases the number of neurons and/or intensity of labeling were diminished in females relative to males. The telencephalic pattern of somatostatin labeling revealed a large number of SS-labeled somata in the magnocellular nucleus of the anterior neostriatum (MAN), the high vocal center (HVC) and the robust nucleus of the archistriatum (RA) of males, whereas female song-control nuclei contained many fewer or no labeled cells in these regions. Area X of the striatum appeared to contain a slightly higher level of somatostatin immunoreactivity than surrounding striatum in males, but the region corresponding to Area X in females could not be distinguished from the rest of striatum. The telencephalic pattern of CGRP staining was less extensive than that seen for SS. In male brains the magnocellular core region of lateral MAN contained many darkly labeled neurons, and RA was stained by a dense field of anterograde terminal label. Well labeled somata were also seen in medial MAN of males, but HVC was devoid of immunoreactivity. Area X in male brains contained a light field of terminal immunoreactivity. The pattern of labeling seen in males indicates that CGRP acts selectively as a neuromodulator along the efferent projection from lateral MAN to RA and Area X but not in the HVC-to-RA pathway. No telencephalic song-control nuclei in female brains contained CGRP staining. Although some diencephalic and midbrain nuclei contained well-labeled somata or fibers with either or both neuropeptides, there was little or no evidence of a sex difference in neuropeptide expression in these regions. This latter finding suggests that the greater anatomical specialization seen in cortical regions of songbirds compared to those regions in non-oscine species is accompanied by a greater neurochemical differentiation, whereas thalamic and midbrain regions may be more conserved across sex as well as species. These findings indicate that male neurons produce high levels of somatostatin and calcitonin gene-related peptide in major telencephalic vocal-control regions in zebra finches, whereas female neurons produce less or none at all. These dramatic neurochemical sex differences may be directly related to production of learned vocalizations in males, as well as to other aspects of song behavior and courtship.

ISSN:0006-8977    

DOI:10.1159/000113342

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

This study examined the distribution of the neuropeptides somatostatin (SS) and calcitonin gene-related peptide (CGRP) in forebrain and midbrain song-control nuclei of male versus female brains in adult zebra finches (Poephila guttata) using immunohistochemical techniques. Vocal learning in songbirds is controlled by an interconnected, highly-localized system of brain nuclei. Male zebra finches produce learned vocalizations, and females do not. This behavioral sexual dimorphism is reflected in a substantial difference in the size of these song-control nuclei: males have larger nuclei containing a greater number of neurons than do females. Interestingly, previous studies describing neurochemical aspects of the song-control system in other songbird species have not reported any obvious sex differences. However, the results of this study showed that the level of neuropeptide staining was substantially greater in telencephalic song-control nuclei of male brains compared to female brains in zebra finches. In some brain regions females lacked any apparent staining, whereas male brains were intensely labeled. In other cases the number of neurons and/or intensity of labeling were diminished in females relative to males. The telencephalic pattern of somatostatin labeling revealed a large number of SS-labeled somata in the magnocellular nucleus of the anterior neostriatum (MAN), the high vocal center (HVC) and the robust nucleus of the archistriatum (RA) of males, whereas female song-control nuclei contained many fewer or no labeled cells in these regions. Area X of the striatum appeared to contain a slightly higher level of somatostatin immunoreactivity than surrounding striatum in males, but the region corresponding to Area X in females could not be distinguished from the rest of striatum. The telencephalic pattern of CGRP staining was less extensive than that seen for SS. In male brains the magnocellular core region of lateral MAN contained many darkly labeled neurons, and RA was stained by a dense field of anterograde terminal label. Well labeled somata were also seen in medial MAN of males, but HVC was devoid of immunoreactivity. Area X in male brains contained a light field of terminal immunoreactivity. The pattern of labeling seen in males indicates that CGRP acts selectively as a neuromodulator along the efferent projection from lateral MAN to RA and Area X but not in the HVC-to-RA pathway. No telencephalic song-control nuclei in female brains contained CGRP staining. Although some diencephalic and midbrain nuclei contained well-labeled somata or fibers with either or both neuropeptides, there was little or no evidence of a sex difference in neuropeptide expression in these regions. This latter finding suggests that the greater anatomical specialization seen in cortical regions of songbirds compared to those regions in non-oscine species is accompanied by a greater neurochemical differentiation, whereas thalamic and midbrain regions may be more conserved across sex as well as species. These findings indicate that male neurons produce high levels of somatostatin and calcitonin gene-related peptide in major telencephalic vocal-control regions in zebra finches, whereas female neurons produce less or none at all. These dramatic neurochemical sex differences may be directly related to production of learned vocalizations in males, as well as to other aspects of song behavior and courtship.

ISSN:0006-8977    

DOI:10.1159/000316297

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

Bombesin is a member of a class of neuroactive chemicals that have potent thermoregulatory effects in ectothermic and endothermic vertebrate species. Bombesin-like peptides are found in the brains of ectothermic and endothermic vertebrates and have been implicated in the central nervous system modulation of behavioral thermoregulation. Amphibians rely on behavioral thermoregulation to maintain their body temperature within developmental stage-dependant critical limits. To investigate the influence of bombesin on behavioral thermoregulation, we examined the effects of central injections of bombesin on thermal habitat selection at different stages of bullfrog development. Tadpoles and adult male and female frogs were allowed to select a preferred temperature, within an aquatic thermal gradient, before and after receiving an intracerebroventricular injection of bombesin. In larval and adult female bullfrogs, bombesin administration caused a decrease in preferred temperature values. This effect was clearly dose-dependent in tadpoles. Bombesin effects were variable in adult males, probably due to an overriding stress response to handling exhibited by males. The bombesin-induced hypothermia was blocked by [D-Phe6, Des-Met14]-bombesin (6–14), ethyl amide, a bombesin/gastrin-releasing peptide receptor antagonist. These data suggest that bombesin/gastrin-releasing peptide receptors are functional in the central nervous system of larval and adult amphibians and that receptor binding can modulate thermoregulation. They raise the question: under what natural conditions is endogenous bombesin/gastrin-releasing peptide released in the brain to activate thermoregulatory behavior?

ISSN:0006-8977    

DOI:10.1159/000113343

出版商:S. Karger AG    

年代:1997

数据来源: Karger