Sex-related differences in pineal gland N-acetyltransferase induction by d-amphetamine

The activity of the rat pineal gland enzyme, N-acetyltransferase (NAT), was measured to determine if amphetamine stimulation of norepinephrine release from sympathetic fibers innervating the gland varies according to sex-dependent mechanisms. Pineal gland NAT activity was increased following amphetamine treatment to a greater extent and for a longer duration in adult female rats compared to male animals. The greater in vivo stimulation of adult female pineal gland NAT activity by the drug developed after puberty, depended upon intact gonads, and apparently was not due to sex differences in the amount of norepinephrine released by the drug from sympathetic nerves when tested under in vitro conditions. The in vivo sex dependent effects of amphetamine may be related to the lesser rate at which the drug is metabolized and/or excreted by female rats compared to males.