Autoradiographic analyses of the effects of restraint-induced stress on 5-HT1A, 5-HT1C and 5-HT2 receptors in the dorsal hippocampus of male and female rats.

Quantitative autoradiography was used to evaluate the effects of sex and either 1 or 5 daily 2-hour sessions of restraint stress on binding at 5-HT1A, 5-HT1C and 5-HT2 receptors in the rat dorsal hippocampus. Neither sex nor restraint stress were found to have effects on binding at 5-HT1C or 5-HT2 receptors. However, restraint stress increased binding of [3H]8-hydroxy-2-(di-n-propylamino)tetralin at 5-HT1A receptors in the CA4 region and in the infrapyramidal dentate gyrus. In addition, levels of binding at 5-HT1A receptors in the oriens and lacunosum moleculare layers of the CA1 region were significantly higher in female rats. Neither estradiol benzoate nor estradiol benzoate plus progesterone had effects on binding at hippocampal 5-HT1A receptors in ovariectomized rats, making it unlikely that the sex differences were related to stages of the estrous cycle. Stress-induced levels of corticosterone (CORT) were higher in females. Although CORT levels in blood obtained during restraint decreased from session 1 to session 5 in both male and female rats, the decrease became significant in females only. Female rats also displayed higher levels of activity in the open field. Although activity in the open field was reduced in male and female rats after restraint, these decreases were not significant. Results are discussed in relation to anxiety and depression.