Low doses of cocaine decrease, and high doses increase, anxiety-like behavior and brain progestogen levels among intact rats

Abstract

There are sex and hormonal differences in response to cocaine that have been demonstrated in people and animal models. Cocaine can alter secretion of progestogens, such as progesterone (P), and its neuroactive metabolite, 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP). However, little research has been done on the neuroendocrine effects in the initiation phase of cocaine use. We hypothesize that some sex/hormonal differences in initiation phase responses to cocaine may be related to formation of progestogens. To investigate the role of progestogens in sex differences in response to acute cocaine, male and female rats in the high (proestrous) or low (diestrous) progestogen phase of the estrous cycle were administered cocaine (0, 5, 10, or 20mg/kg, IP). We examined cocaine's acute neuroendocrine effects on P and 3alpha,5alpha-THP levels, as well as its effects on acute psychomotor stimulation, anxiety, and sexual behaviors. Among rats that had P and/or 3alpha,5alpha-THP levels increased in response to cocaine, enhanced acute psychomotor stimulation was observed. Results suggest that cocaine produces U-shaped curves for progestogens, and anxiety-like behaviors. Male rats were less susceptible to these effects of cocaine than were proestrous or diestrous female rats. However, cocaine's disruption of sexual behaviors was similar among males and proestrous females. These data suggest a complex interaction between hormonal milieu and the neuroendocrine and behavioral effects of cocaine.

Fig. 1

Left panel depicts total entries in the open field of diestrous female, proestrous female and male rats (n=9–12/group) administered cocaine (0, 5, 10, or 20 mg/kg, IP). Right panel depicts time spent in the center of the open field among diestrous female, proestrous female, and male rats (n=9–12/group) administered cocaine (0, 5, 10, or 20 mg/kg, IP). * indicates significant differences from respective vehicle-administered control group.

Fig. 2

Sexual behaviors of diestrous female, proestrous female and male rats (n=9–12/group) administered cocaine (0, 5, 10, or 20 mg/kg, IP). * indicates significant differences from respective vehicle-administered control group.