Sex differences in GABA/benzodiazepine receptor changes and corticosterone release after acute stress in rats

Since many hormonal indices of stress responsiveness are sexually dimorphic in rats, we examined sex differences and the effects of gonadectomy on the stress-related changes in GABA_A/benzodiazepine receptors in rats. Intact or ovariectomized female rats displayed a markedly greater corticosterone response and a more pronounced increase in benzodiazepine receptors than males (intact or orchidectomized) after acute handling or swim stress. Swim stress increased benzodiazepine receptor density without modifying affinity in cortex, hippocampus, and hypothalamus. Corticosterone treatment induced benzodiazepine receptor levels comparable to those seen after swim stress in all hormone groups. Handling stress also enhanced cortical low-affinity GABA_A receptor levels in males and ovariectomized females. Both GABA and benzodiazepine receptor levels were positively correlated with circulating corticosterone levels in female, but not male, groups. GABA/benzodiazepine coupling was unaffected by stress or hormonal status. These sexual dimorphisms in hormonal responses to stress may help elucidate the causes and consequences of stress-induced changes in the GABA_A/benzodiazepine receptor complex.