Dimorphic distribution of the two main GABAA binding sites in cortical and limbic areas of a rodent living in natural environmental conditions
✍ Scribed by Canonaco, Marcello; Tavolaro, Renata; Facciolo, Rosa Maria
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 369 KB
- Volume
- 380
- Category
- Article
- ISSN
- 0021-9967
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✦ Synopsis
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.