Ovarian responses to perphenazine-induced prolactin secretion in the rats: Effect of ovulation, stress, and steroids.

A single injection of 2.5 mg perphenazine (PH)/kg body wt to rats on the day of estrus (day 0) did not result in increased serum progesterone 24 hr later. Continued daily injections, however, resulted in a 2.5-fold increase in serum progesterone between days 1 and 3 and a 1.6-fold increase between days 3 and 5 to a final concentration of 58 plus or minus 4 ng/ml on day 5 in serially anesthetized and bled rats. Neither daily administration of 5.0 nor 10.0 mg PH/kg body wt to rats subjected to the stressful conditions of this regimen resulted in further increases in serum progesterone, but the 5.0 mg dose of PH in unstressed rats bled only on day 5 resulted in a highly significant increase in serum progesterone to 110 plus or minus 7 ng/ml. In unstressed rats the increase in serum progesterone over control values after five daily injections of 2.5 mg PH/kg body wt could be attributed to decreased 20alpha-reduction of progesterone, but when the dose of PH was increased to 5.0 mg/kg, a highly significant increase in both progesterone and total progestins occurred indicating that prolactin can increase steroidogenesis as well as reduce 20alpha-hydroxysteroid dehydrogenase activity. After inhibition of ovulation, the 5.0 mg daily dose of PH resulted in serum progesterone of only 25 plus or minus 8 ng/ml on day 5 in unstressed rats. Thus, serum progesterone in ovulating rats treated with PH originated primarily in the corpora lutea. Perphenazine, 5.0 mg/kg, administered only on estrus and the first day of diestrus was sufficient to induce pseudopregnancy of 14.5 plus or minus 1.6 days. No evidence for gonadotropin stimulation of the ovaries of any rats was observed. The effect of stress on the progesterone response was not mimicked by administration of cortisol acetate and is assumed to be medicated by suppression of prolactin secretion.