The serum and pituitary prolactin variations under the influence of a pesticide substance in the male rat.

Prolactin was measured in the serum and hypophysis of the male rat after five days of oral administration of malathion in suspension (200 mg/kg body), alone or associated with pimozide (a psychotropic drug). The release of prolactin observed in the group treated with malathion was lower (19.97 +/- 7.27 ng/ml) than in the groups treated with malathion and pimozide or pimozide alone (26.65 +/- 3.17 and 26.49 +/- 2.57 ng/ml, respectively) but significantly higher than in the control group (10.08 +/- 5.82 ng/ml). The administration of two dose levels of pure malathion solubilized in alcohol/water (v/v) failed to reproduce the same results. The discussions are focussed upon: 1) the mechanisms involved in the release of prolactin under the influence of malathion (vagomimetic action) and 2) the lack of cumulative effects of malathion and pimozide (presumably different levels of their influence).