Effects of benztropine mesylate on haloperidol-induced prolactin secretion and serum haloperidol levels in rats.
The effects of benztropine mesylate on haloperidol-induced prolactin secretion and serum haloperidol levels were investigated in 240 rats. Animals were pretreated with benztropine mesylate or saline 20 min prior to receiving haloperidol or saline. Serum prolactin and haloperidol levels were analyzed at six time periods over 150 min. There was no significant difference in prolactin levels of control animals, i.e., saline pretreated/saline treated rats compared to benztropine mesylate pretreated/saline treated rats. Haloperidol caused a significant rise (p less than 0.0001) in serum prolactin compared with controls. The prolactin concentration for the 30-150-min sampling period was significantly higher when the rats received benztropine mesylate prior to haloperidol (p less than 0.05). There was a significant correlation (r = 0.57, p less than 0.001) between serum haloperidol levels and serum prolactin levels in haloperidol-treated animals pretreated with either saline or benztropine mesylate. Additionally, serum haloperidol levels were not significantly different in animals pretreated with benztropine mesylate compared with those pretreated with saline. Thus, the enhancement of prolactin levels by benztropine mesylate was independent of any effect of haloperidol metabolism. This study appears to indicate that in the rat, cholinergic mechanisms exert a weak inhibitory effect on prolactin secretion under conditions of dopamine blockade.
D000818:Animals; D001590:Benztropine / Q000031:analogs & derivatives / Q000494:pharmacology*; D006220:Haloperidol / Q000097:blood / Q000494:pharmacology*; D008297:Male; D010276:Parasympatholytics / Q000494:pharmacology*; D011388:Prolactin / Q000378:metabolism*; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors; D014326:Tropanes / Q000494:pharmacology*
D010276:Parasympatholytics; D014326:Tropanes; D001590:Benztropine; D011388:Prolactin; D006220:Haloperidol