Effects of drugs on brain neurotransmitter and pituitary-testicular function in male rats

The effects of different drugs influencing brain neurotransmitter contents have been tested on the pituitary-testicular function in male rats. L-dopa (200 mg/kg body weight, i.p.) increased the dopamine and noradrenaline contents of the hypothalamus, amygdala, striatum and mesencephalon, but it was ineffective as regards the 5-hydroxytryptamine contents of the same brain areas, and increased the plasma testosterone level. alpha-Methyl-p-tyrosine (250 mg/kg b.w., i.p.) decreased the dopamine and noradrenaline contents of these brain areas, but it was ineffective to 5-hydroxytryptamine, and decreased the plasma testosterone level. Diethyldithiocarbamate (400 mg/kg b.w., i.p. twice a day) increased the dopamine levels in the hypothalamus, amygdala, striatum and mesencephalon, decreased the noradrenaline contents in the same brain regions but had no effect on the 5-hydroxytryptamine contents of these brain areas or on the testosterone level in the peripheral blood. p-Chlorophenylalanine (300 mg/kg b.w., i.p.) decreased the 5-hydroxytryptamine contents of the different brain areas, while it had no effect on the dopamine and noradrenaline levels or on the plasma testosterone level. 5-Hydroxytryptophan (200 mg/kg b.w., i.p.) increased the 5-hydroxytryptamine contents of all brain areas studied, but was without effect on the dopamine and noradrenaline contents or the plasma testosterone level. The data suggest that both dopamine and noradrenaline may be involved in the regulation of the pituitary-testicular function, and the ratio of the two transmitters might be more important that their actual levels in definite brain areas.