摘要:

Amphibians rely exclusively on behavioral thermoregulation to maintain body temperature within species- and developmental stage-specific critical limits. Several members of the bombesin family of peptides and histamine are included in a class of neurochemicals that have potent thermoregulatory effects in ectothermic and endothermic vertebrate species and may be involved in behavioral thermoregulation in amphibians. Because amphibians respond to environmental temperature cues differently in larval versus adult animals, we used immuno-cytochemistry to study developmental changes in bombesin-like (BN) and histamine-like (HA) innervation in the bullfrog brain and spinal cord. Neurons and fibers that were BN-immunoreactive and HA-immunoreactive were present in the earliest stage tadpoles examined (Gossner stage 29); BN-immunoreactive perikarya were found only in the preoptic area, posterior thalamic nucleus and in the rostroventral tegmentum of the mesencephalon. In the preoptic area, dramatic changes were observed in the number and staining intensity of BN-ir so-mata; neuronal labelling was greatest in tadpoles undergoing tail resorption (i.e. metamorphic climax) and was nearly absent in adults. Neurons immunoreactive to BN in the ventral mesencephalon also were developmental stage-dependent; limb-bud growth stage tadpoles had the largest numbers of labelled neurons, whereas in the adults, labelled cells were rarely visible in this area. The highest density of fibers was in the medial septum, lateral amygdala, and the optic tectum. Fewer fibers were observed within the dorsal and ventral hypothalamus, the pineal gland, and all the thalamic nuclei. Perikarya immunoreactive to HA were localized in the dorsal infundibular nucleus of the hypothalamus. Immunoreactivity was present in all developmental stages examined, and the numbers of labelled cells increased throughout metamorphosis to a maximum in adult brains. Fibers were found in the medial septum, medial amygdala, preoptic area, thalamus, pineal gland, hypothalamus and optic tectum. These results show that BN- and HA-immunoreactivities are established early in larval development, but their phenotypes are differentially expressed during larval and adult growth stages. This pattern suggests that reorganization of BN-like and HA-like neural circuitry may occur during metamorphosis and may be involved in the reported developmental changes in amphibian thermoregulation. In addition, BN-like peptides and HA may modulate other related mechanisms of amphibian thermoregulation and behaviour, such as thermal acclimation, circadian shifts in temperature selection and feeding. To what extent they are involved in amphibian thermoregulation remains to be investigated.

ISSN:0006-8977    

DOI:10.1159/000112982

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

This paper presents and reviews data suggesting that the dorsal thalamic zone (abbreviated DTZ) in birds is homologous to the intralaminar, midline, and mediodorsal thalamic nuclear complex (abbreviated IMMC) in mammals. The DTZ is located dorsomedially in the diencephalon of birds and consists of several subnuclei: nucleus dorsomedialis anterior thalami (DMA), nucleus dorso-medialis posterior thalami (DMP), nucleus dorsolateralis anterior thalami, pars medialis (DLM), nucleus dorsointermedius posterior thalami (DIP), nucleus dorsolateralis posterior thalami (DLP), and nucleus subhabenularis lateralis (SHL). Our immunohistochemical studies show that: (1) SHL and medial and dorsal parts of DMA and DMP are relatively rich in GABAergic, enkephalin-containing, substance P-containing, and cholinergic fibers; (2) lateral parts of DMA and DMP are relatively poor in these neurotransmitters; and (3) DIP, DLP, and DLM are moderately rich in cholinergic and substance P-containing fibers. Our retrograde pathway tracing studies indicate that the DIP and DLP in the more lateral parts of DTZ project to somatic striatum, while the DMA, DMP, and SHL located more medially in the DTZ project to visceral/limbic striatum. Our anterograde tracing studies indicate that DIP receives afferents from the dorsal pallidum, whereas DMA and DMP appear to receive afferents from both the ventral striatum and ventral pallidum. Diverse prior studies have shown that in general medial and lateral components of DTZ are connected with visceral/ limbic and somatic brain regions, respectively. These characteristics indicate that: (1) SHL and medial and dorsal parts of DMA and DMP are comparable to mammalian midline thalamic nuclei, including the medial components of the intralaminar nuclei; (2) lateral parts of DMA and DMP are comparable to the mediodorsal nucleus in mammals; (3) DIP is comparable to the parafascicular nucleus in mammals; and (4) DLM and DLP are comparable to the laterally located intralaminar nuclei in mammals. The comparability of avian DTZ and mammalian IMMC suggests that they evolved from thalamic precursor nuclei present in the common reptilian ancestors and that they may perform similar roles in the movement control function of the basal ganglia.

ISSN:0006-8977    

DOI:10.1159/000112983

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

This paper presents and reviews data suggesting that the dorsal thalamic zone (abbreviated DTZ) in birds is homologous to the intralaminar, midline, and mediodorsal thalamic nuclear complex (abbreviated IMMC) in mammals. The DTZ is located dorsomedially in the diencephalon of birds and consists of several subnuclei: nucleus dorsomedialis anterior thalami (DMA), nucleus dorso-medialis posterior thalami (DMP), nucleus dorsolateralis anterior thalami, pars medialis (DLM), nucleus dorsointermedius posterior thalami (DIP), nucleus dorsolateralis posterior thalami (DLP), and nucleus subhabenularis lateralis (SHL). Our immunohistochemical studies show that: (1) SHL and medial and dorsal parts of DMA and DMP are relatively rich in GABAergic, enkephalin-containing, substance P-containing, and cholinergic fibers; (2) lateral parts of DMA and DMP are relatively poor in these neurotransmitters; and (3) DIP, DLP, and DLM are moderately rich in cholinergic and substance P-containing fibers. Our retrograde pathway tracing studies indicate that the DIP and DLP in the more lateral parts of DTZ project to somatic striatum, while the DMA, DMP, and SHL located more medially in the DTZ project to visceral/limbic striatum. Our anterograde tracing studies indicate that DIP receives afferents from the dorsal pallidum, whereas DMA and DMP appear to receive afferents from both the ventral striatum and ventral pallidum. Diverse prior studies have shown that in general medial and lateral components of DTZ are connected with visceral/ limbic and somatic brain regions, respectively. These characteristics indicate that: (1) SHL and medial and dorsal parts of DMA and DMP are comparable to mammalian midline thalamic nuclei, including the medial components of the intralaminar nuclei; (2) lateral parts of DMA and DMP are comparable to the mediodorsal nucleus in mammals; (3) DIP is comparable to the parafascicular nucleus in mammals; and (4) DLM and DLP are comparable to the laterally located intralaminar nuclei in mammals. The comparability of avian DTZ and mammalian IMMC suggests that they evolved from thalamic precursor nuclei present in the common reptilian ancestors and that they may perform similar roles in the movement control function of the basal ganglia.

ISSN:0006-8977    

DOI:10.1159/000316285

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

In the little skate, Raja erinacea, the electrosensory primary afferents are responsive to electrical potentials created during the animal's own ventilation, while second-order electrosensory cells in the dorsal nucleus of the medulla suppress the responses to ventilatory potentials but retain their extreme sensitivity to important environmental electric signals. Previous electrophysiological studies indicate a role for a commissural pathway between the bilateral dorsal nuclei in ventilatory noise suppression. In the present study, retrograde tracers were used to label dorsal nucleus commissural cells. Large round or triangular and thin elongate commissural cells occur in the central zone of the dorsal nucleus where the primary afferent fibers terminate. Elongate commissural cells also occur in the peripheral zone which is the cell body area of the major efferents of the dorsal nucleus. Immunohistochemical studies indicate that stellate cells of the molecular layer and round or triangular cells of the central zone comprise the GABA-immunoreactive cell groups of the dorsal nucleus. A subpopulation of the round commissural cells in the central zone are GABA-immunoreactive and may be candidates for mediators of common-mode noise rejection in the dorsal nucleus of skates. The non-GABAergic commissural cells may mediate crossed inhibition through an inhibitory transmitter other than GABA or may supply crossed excitation to the dorsal nucleus.

ISSN:0006-8977    

DOI:10.1159/000112984

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

Previous studies have shown that those food-storing birds of the order Passeriformes that remember the locations of their caches have relatively larger hippocampal complexes than do non-storing passerines. Woodpeckers constitute a different avian order (Piciformes), which also includes some food-storing species. We compared hippocampal volume, relative to the volume of the rest of the telencephalon, across four species of woodpeckers with disparate caching behavior. Red-bellied woodpeckers (Melanerpes carolinus) are 'scatter hoarders'. During the fall and winter they cache acorns or beechnuts in dispersed sites throughout a large territory. Red-headed woodpeckers (Melanerpes erythrocephalus) also store nuts but in central 'larders' on their small territories which they fiercely defend. Caching is absent or much reduced in hairy woodpeckers (Picoides villosus) and downy woodpeckers (Picoides pubescens), both of which forage on a variety of foods within large winter home ranges. The relative volume of the hippocampal complex in the scatter hoarder was larger than in the larder hoarder, suggesting that red-bellied woodpeckers, like passerine scatter hoarders, rely on memory to recover their caches. Surprisingly, the relative hippocampal volumes in the two non-storing Picoides woodpeckers were most similar to the scatter hoarder of the other genus. In passerine birds, hippocampal volume and telencephalon volume are highly correlated in storing species but not in non-storers. We found that the volumes of these two brain areas were highly correlated in both Melanerpes species, uncorrected in the hairy woodpeckers, and more weakly correlated in the downy woodpeckers. The unexpectedly large hippocampal complexes in the Picoides species suggests they may engage in some behavior, other than food-storing, that selects for this trait. Conversely, our results concerning the relationship between hippocampal and telencephalon volumes may indicate that a weak correlation is associated with a less specialized hippocampus, independent of its relative volume.

ISSN:0006-8977    

DOI:10.1159/000112985

出版商:S. Karger AG    

年代:1997

数据来源: Karger