Effects of Gonadectomy and Avoidance Learning on the GABAAα1 Receptor Density in the Prefrontal Cortex of Male and Female Rats

We evaluated the effects of gonadectomy and passive avoidance learning on the density of GABA(A alpha 1) receptors in the prefrontal cortex of male and female rats. Twenty adult males weighing 200 +/- 30 g and 20 adult females weighing 150 +/- 20 g were divided into four groups: (i) Sham, intact rats with no learning session, (ii) Sham-L, intact rats subjected to the avoidance learning session, (iii) GE, gonadectomized rats without learning, and (iv) GE-L, gonadectomized rats with learning. A shuttle box was used for the induction of passive avoidance learning. The density of GABA(A alpha 1) receptors was investigated with an immunohistochemical technique; Image Analyzer software was used. Ovariectomy without learning led to significant reduction of the density of GABA(A alpha 1) receptors in different regions of the prefrontal cortex relative to the control intact group; at the same time, ovariectomized females with learning demonstrated a significantly higher density of GABA(A alpha 1) receptors in the prefrontal cortex as compared to the Sham group. No significant differences in the density of GABA(A alpha 1) receptors were observed in both castrated male rat groups. The comparison of male and female rats showed that the density of GABA(A alpha 1) receptors in castrated rats with learning was significantly lower than that in ovariectomized females with learning. Thus, ovariectomy exerts a more potent effect than castration on the GABA(A alpha 1) receptor density in different regions of the prefrontal cortex. Learning provides increases in the GABA(A alpha 1) receptor density in different regions of the prefrontal cortex in female rats, while castration of male rats exerts no significant effect from this aspect.