Gamma-aminobutyric acid-immunoreactive neurons in the amygdala of the rat - sex differences and effect of early postnatal castration.

The distribution of GABA-immunoreactive neurons in the rat amygdala was determined by immunohistochemical methods. Sex differences in the number of GABA-immunoreactive cell bodies were observed in the medial, central, cortical and basolateral amygdaloid nuclei. Females had more numerous GABA-expressing neurons than males (P < 0.01). Castration of neonatal males had controversial effects on this sex difference in the different parts of the amygdaloid complex. In the cortical and basolateral amygdala castrated males showed a female pattern of GABA-expression. In the central amygdala no effect of castration on the number of GABA-immunoreactive cells was found. In the medial amygdaloid nucleus numbers of GABAergic neurons in castrated males differed both from intact males and females. The results of the present study suggest that the expression of GABA in the neurons of the amygdala is under complicated gonadal hormone regulation.