Effects of cortisol and cocaine on plasma prolactin and growth hormone levels in cocaine-dependent volunteers.
In rodents, corticosterone (cortisol in humans) facilitates cocaine self-administration purportedly via enhancement of dopaminergic activity in the brain. This study sought to assess central dopaminergic effects of cortisol in humans and to compare them to those of cocaine. Twelve cocaine-dependent individuals received an intravenous bolus of cortisol (0.5 and 0.2 mg/kg; n=6 for each dose) and cocaine (0.2 mg/kg) in a double-blind randomized placebo-controlled and counterbalanced fashion. Their plasma was assayed over the next 120 min for prolactin and growth hormone (GH), which are two neuroendocrine indices of dopaminergic function. Cortisol injections produced significant increases in GH, while cocaine resulted in significant decreases in prolactin. Placebo administration was associated with gradual declines in prolactin, but the levels at the 90- and 120-min time points were significantly lower after cocaine than after placebo infusion. These different neuroendocrine response profiles point to important differences between dopaminergic effects of cortisol and cocaine.