Serum and pituitary prolactin variations under the influence of pyridoxine and pimozide in the male rat.

Prolactin was measured in the serum and hypophyses of the male rat after six days of i.p. administration of pyridoxine 5 mg (group B6), after a single dose of pimozide 2.5 mg/kg body (group PMZ), six days of pyridoxine and one dose of pimozide (group B6- PMZ) and a single dose of tartaric acid (controls). Both pyridoxine and pimozide increased the serum prolactin: 59.06 +/- 16.23 ng/ml and 68.45 +/- 10.78 ng/ml respectively (X +/- DS) by comparison to controls: 33.12 +/- 11.16 ng/ml, their effect being cumulative (83.75 +/- 13.86 ng/ml). However, the effect of pyridoxine and pimozide at the central level is different, pyridoxine producing an increase of the pituitary concentration of prolactin, while pimozide depleted the stored prolactin. Hypothetical mechanisms of pyridoxine action at the pituitary level are discussed.