Effect of Naloxone on the Secretion of Corticosterone Induced by Gamma-Hydroxybutyric Acid in Male Rats

The effect of intraperitoneally administered γ-hydroxybutyrate on the hypothalamo-hypophysial-adrenocortical axis was studied. A significant increase in plasma corticosterone was induced by the administration of γ-hydroxybutyrate (100 mg/kg). The lack of antagonism of this action of γ-hydroxybutyrate by picrotoxin or bicuculline pretreatments (GABAergic antagonists), suggests independence from the GABAergic system. Neither dopaminergic nor serotoninergic systems intervened in the γ-hydroxybutyrate-stimulating effect on the hypothalamo-hypophysial-adrenocortical axis. Both corticosterone release and synthesis in adrenocortical cells was not significantly affected by γ-hydroxybutyrate, suggesting that this is possibly due to a central action of γ-hydroxybutyrate. The increase in corticosterone levels was probably mediated by an opioid receptor, since a strong similarity existed between the effects of γ-hydroxybutyrate and those of morphine. Moreover, the results show that the opioid-receptor involvement was demonstrated by the naloxone-sensitivity of the γ-hydroxybutyrate effects.