Effect of modulating endogenous prolactin secretion on testosterone production in the adult male bonnet monkey (Macaca radiata).

Adult male bonnet monkeys maintained under regulated light: dark conditions exhibit a nycthemeral surge of testosterone. The present study attempts to determine the effect of administration of drugs that modulate prolactin levels like ergobromocriptine (EBC) and chlorpromazine (CPZ) on testosterone production. The injection of EBC, a known inhibitor of prolactin secretion, could abolish nocturnal testosterone surge irrespective of the drug being given at 8.00 or 17.00 h. Testosterone surge could likewise be inhibited by treating animals with CPZ, a potent stimulator of prolactin secretion. This suggests that alteration in endogenous prolactin level from the normal effects nycthemeral surges of testosterone. The in vivo responsiveness of the testes of monkeys injected either CPZ oder EBC to exogenous LH or LHRH stimulation was tested. While LH could completely override the CPZ induced inhibition in testosterone production it could only partially reverse the EBC effect.