The effects of 2-Br-α-ergocryptine (2.5 mg/osM), clonidine (50 μg, intramuscularly) and naloxone (0.4 mg, intramuscularly) as well as the interaction between naloxone and 2-Br-α-ergocryptine or clonidine on luteinizing hormone (LH) follicle-stimulating hormone (FSH), prolactin (PL) and thyroid-stimulating hormone (TSH) serum levels in normal man have been studied. 2-Br-α-erocryptine and clonidine clearly reduce and naloxone tends to reduce PL serum levels. TSH levels are lowered by naloxone as well by clonidine plus naloxone. The results obtained point also to a possible different pattern of LH and FSH secretion after naloxone, that is after opiate receptor blockade. The clonidine effects on PL secretion are discussed in the frame of a possible adrenergic control of the release of this hormone.
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