Salamander GABA

Cross references:  Salamander Neurotransmitters    GABA  
    GABA Metabotropic Receptor   

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    The distribution of GABA-like-immunoreactive neurons in the brain of the newt, Triturus cristatus carnifex, and the green frog, Rana esculenta.  
    "The distribution of gamma-aminobutyric acid (GABA) immunoreactivity was studied in the brain of two amphibian species (Triturus cristatus carnifex, Urodela; Rana esculenta, Anura) by employing a specific GABA antiserum.  
    A noteworthy immunoreactive neuronal system was found in the telencephalic dorsal and medial pallium (primordium pallii dorsalis and primordium hippocampi) and in the olfactory bulbs.  
     In the diencephalic habenular nuclei there was a rich GABAergic innervation, and immunoreactive neurons were observed in the dorsal thalamus.  
    In the hypothalamus the GABA immunoreactivity was found in the preoptic area, the paraventricular organ and in the hypothalamo-hypophysial complex.  
    In the preoptic area of the frog some GABA-immunoreactive CSF-contacting cells were shown. In the optic tectum immunolabeled neurons were present in all the cellular layers. A rich GABAergic innervation characterized both the fibrous layers of the tectum and the neuropil of the tegmentum and interpeduncular nucleus.  
    In the cerebellum, in addition to the Purkinje cells showing a variable immunopositivity, some immunoreactive cells bodies appeared in the central grey. Abundant immunolabeled nerve fibers in the acoustico-lateral area and some immunopositive neurons in the region of the raphe nucleus were observed.  
    In conclusion, the GABAergic central systems, well-developed in the amphibian species studied, were generally characterized by close similarities to the pattern described in mammals."  
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    Spinal cord neuron classes in embryos of the smooth newt Triturus vulgaris: a horseradish peroxidase and immunocytochemical study.  
Spinal cord neurons were investigated in embryos of Triturus vulgaris, the smooth newt, just prior to hatching. These embryos can swim if freed from their egg membranes. Horseradish peroxidase (HRP) labelling, together with GABA and glycine immunocytochemistry (ICC), revealed nine distinct anatomical classes of neuron.  
    1. Ventrolateral motoneurons with mainly dorsal dendrites, sometimes a descending central axon and peripheral axon innervating the trunk muscles.  
    2. Dorsal primary sensory Rohon-Beard neurons innervating skin and with dorsal ascending and descending axons in spinal cord.  
    3. Commissural interneurons with mid-cord unipolar soma, glycine-like immunoreactivity, dendrites on initial segment of ventral axon which crosses cord to ascend or branch.  
    4. Dorsolateral commissural interneurons with multipolar soma in dorsolateral position with dorsal dendrites and ventral axon which crosses and ascends or branches.  
    5. Giant dorsolateral commissural interneurons with large dorsolateral somata widely spaced (130-250 microns spacing) with process projecting dorsally to other side, dorsolateral dendrites and ventral axon which crosses to ascend and branch.  
    6. Dorsolateral ascending interneurons in dorsolateral position with multipolar soma and ascending axon on same side.  
    7. Ascending interneurons with unipolar soma, GABA-like immunoreactivity and ascending axon on same side.  
    8. Descending interneurons with bi- or multi-polar soma, extensive dorsal and ventral dendrites, and descending axon on same side. They may also have ascending axons.  
    9. Kolmer-Agduhr cerebrospinal fluid contacting neurons with cilia and microvilli in lateral corners of neural canal. GABA-like immunoreactivity, no dendrites and ascending axon.  
    Eight of the nine cells classes were found to bear a marked resemblance to neurons previously described in zebrafish and Xenopus embryos in terms of their anatomy, distribution and immunoreactivity to GABA and glycine. Homologies and possible functions are discussed. Giant dorsolateral commissural neurons, were not found in Xenopus or teleosts but were present in Ambystoma mexicanum and Neoceratodus. The regular, possibly segmental longitudinal distribution pattern of these cells within the cord is unusual among amphibian spinal neurons."  
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Steroid modulation of GABAA receptors in an amphibian brain.  
These studies suggest that the steroid recognition sites on GABAA receptors have been highly conserved through vertebrate evolution and thus portend physiologically important functions. However, the pharmacological profiles for the GABAA receptor and the high-affinity corticosteroid receptor are apparently different, suggesting there are multiple types of steroid recognition sites on neuronal membranes."  

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