PROLACTIN RESPONSE TO BUSPIRONE CHALLENGE IN THE PRESENCE OF DOPAMINERGIC BLOCKADE

Buspirone-stimulated prolactin release has been employed as an indirec t measure of central serotonin activity; however,, it is not clear whe ther serotonergic or dopaminergic systems are responsible for this res ponse. In an attempt to further elucidate the mechanism, we studied th e prolactin response to buspirone in eight subjects in the presence of maximal dopaminergic receptor blockade with metoclopramide under plac ebo-controlled, double-blind conditions, The prolactin response to bus pirone in the presence of metoclopramide was not statistically differe nt from that to placebo under the same conditions, The demonstration o f further prolactin release by a bolus of thyrotropin-releasing hormon e under maximal dopaminergic receptor blockade provided evidence again st potential pituitary prolactin depletion by metoclopramide. These re sults lend further support to a dopaminergic mechanism in buspirone-in duced prolactin secretion; therefore, further caution is warranted in interpreting the results of this challenge test as a measure of seroto nergic activity in the brain.