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Dimorphic distribution of the two main GABA A binding sites in cortical and limbic areas of a rodent living in natural environmental conditions
Author(s) -
Caaco Marcello,
Tavolaro Renata,
Facciolo Rosa Maria
Publication year - 1997
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/(sici)1096-9861(19970421)380:4<423::aid-cne1>3.0.co;2-3
Subject(s) - muscimol , basolateral amygdala , gabaa receptor , nucleus , biology , amygdala , neuroscience , anatomy , cortex (anatomy) , endocrinology , medicine , hippocampus , chemistry , receptor , biochemistry
Labeling of the two more important gamma‐aminobutyric acid A (GABA A ) supramolecular sites with [ 3 H] muscimol (GABA A ) and [ 3 H] flunitrazepam (benzodiazepine) provided saturable, stable, and dimorphic binding activities in cortical and limbic regions of the wood mouse Apodemus sylvaticus . Of the cortical layers, which contained the highest [ 3 H] muscimol binding levels, only the female lamina V supplied a greater (51%; P <0.01) receptor density than in the male. Areas of the limbic system instead proved to be the more favorable targets for differential GABA A binding levels. The highest ( P <0.001) and higher levels were found in the oriens‐pyramidalis CA1 layer of the hippocampus (65%) and in the vertical limb diagonal band‐medial septal nucleus (48%), basolateral amygdala nucleus (45%), and ventromedial hypothalamic nucleus (43%), respectively, of the female. A similar pattern was obtained for [ 3 H] flunitrazepam binding activity, especially in the presence of GABA. The highest and higher binding activities were obtained in the female central amygdala nucleus (78%) and in the ventromedial hypothalamic nucleus (52%), basolateral amygdala nucleus (48%), and oriens‐pyramidalis CA1 layer of the hippocampus (47%), respectively, whereas higher levels were observed only in the male vertical limb diagonal band‐medial septal nucleus (56%). Even in the cortical regions, the female exhibited higher (42%; cortex lamina V) and moderately higher (38%; cortex lamina VI) levels, with binding differences in the latter site plus in the basolateral amygdala nucleus occurring in a GABA‐nondependent manner. From the saturation binding analyses it was possible to reveal that both maximal number of binding sites (B max ) and mean dissociation constant (K D ) modifications were responsible for receptor differences of the two GABAergic sites. These findings tend to suggest that dimorphic variations of the GABA A supramolecular sites, in some cortical and limbic regions, are strongly involved in sex‐specific aggressive and reproductive activities of rodents living in their natural habitats. J. Comp. Neurol. 380:423–434, 1997. © 1997 Wiley‐Liss, Inc.