Action of androgenic steroids on brain neurotransmitters in rats

The effects of androgenic steroids on the dopamine (DA), noradrenaline (NA) and 5-hydroxytryptamine (5-HT) contents of different brain regions have been studied in order to elucidate the possible involvement of neurotransmitters in the negative feedback action of androgens. Administration of testosterone propionate (TP); (100 micrograms/kg or 5 mg/kg, i.p.) increased plasma testosterones, which reached a maximum at about 30 min following injections. TP (100 micrograms/kg) decreased the DA level in the hypothalamus to a minimum after 30 min and returned to normal level after 120 min. There was no effect in the amygdala, striatum and mesencephalon. Subsequent to 5 mg/kg i.p. TP administration, the minimum in the DA level was observed between 90 and 120 min in the hypothalamus, and after 120 min in the amygdala, but the treatment was without effect in the striatum and mesencephalon. Both doses of TP were ineffective as regards for in altering NA and 5-HT levels in the brain areas studied. In a dose of 5 mg/kg, androgens of different activities, such as norandrostenolone, dihydrostestosterone and androstenedione, decreased the DA contents of the hypothalamus and amygdala regions, but pregnenolone was ineffective. None of the androgens affected the NA and 5-HT levels in the brain areas studied. The data suggest that some of the actions of androgens are mediated via a dopaminergic mechanism in which not only the hypothalamus but also the amygdala is involved.