Effects of long-term treatment with contraceptive steroids on plasma and brain tryptophan, brain 5-hydroxytryptamine, and locomotor activity in female mice [proceedings].

Abstract

The effects of prolonged daily injections of norethistrone acetate (200 mcg/kg) alone and in combination with ethinyl estradiol (100 mcg/kg) were compared with daily vehicle injection. Locomotor activity was determined continuously for 2 estrus cycles prior to injection, the every 7th day throughout 42 days of treatment. Free and total plasma tryptophan and brain tryptophan and 5-HT (serotonin) were determined on the 43rd day and compared with diestrous values. Locomotor activity declined after both treatments. The norethistrone group had 47% of activity. The combination group was 54% of initial diestrus values. Vehicle controls resumed cyclic changes in locomotor activity within 8 days, while the hormone treatments abolished these cyclic changes. Norethistrone was ineffective in changing brain tryptophan values. The combined treatment caused the reduction of plasma total and free tryptophan, probably due to acceleration of protein synthesis.