INTRAVENOUSLY INFUSED SUBSTANCE-P IS UNABLE TO CHANGE BASAL AND TRH-STIMULATED PRL SECRETION IN NORMAL MEN

In order to test the possible effects of an intravenous administration of substance P (SP) on basal and TRH-stimulated PRL release, SP was i nfused alone (0.5 or 1.5 pmol/kg-1/min-1 for 60 min) or after TRH (20 or 400 mug in an i.v. bolus) in 21 normal male subjects. In addition, plasma cortisol levels during SP infusion were measured. In agreement with previous findings, a significant increase in plasma cortisol leve ls was observed when the higher (1.5 pmol/kg-1/min-1) but not the lowe r (0.5 pmol/kg-1/min-1) amount of SP was given. In contrast, basal and TRH (20 or 400 mug)-induced PRL release were not modified by SP at an y tested amount. These data suggest that, in normal men, plasma SP is not involved in the control of PRL release at the anterior pituitary l evel.