Intracerebroventricular injection of cholecystokinin octapeptide elevates plasma prolactin levels through stimulation of vasoactive intestinal polypeptide.
We investigated the effect of cholecystokinin octapeptide (CCK-8) on plasma PRL levels in freely moving male rats. Intravenous injection of CCK-8 did not affect basal plasma PRL levels in doses up to 5000 ng/rat; however, plasma PRL increased significantly after intracerebroventricular (icv) injection of the peptide at a dose of 40 ng/rat. Proglumide (0.2 mg/kg, iv) and benzotript (0.2 mg/kg, iv), specific CCK receptor antagonists, blocked the icv CCK-8-induced increase in plasma PRL levels. There was no apparent effect of icv CCK-8 on the enhancement of PRL release by haloperidol (0.2 mg/kg, iv), sulpiride (0.1 mg/kg, iv), domperidone (0.1 mg/kg, iv), or RO22-1319 (0.1 mg/kg, iv). However, the apomorphine-induced inhibition of PRL secretion was significantly antagonized by icv CCK-8. Furthermore, icv CCK-8 increased plasma PRL levels in rats depleted of dopamine by pretreatment with reserpine and alpha-methyl-p-tyrosine. Finally, the elevation in plasma PRL levels produced by icv CCK-8 was substantially antagonized by vasoactive intestinal polypeptide antiserum (1:3; 10 microliter/rat, icv). These results suggest that CCK-8 increases plasma PRL through an interaction with a central CCK receptor, which stimulates the activity of vasoactive intestinal polypeptide, a putative PRL-releasing factor.
Tanimoto
K
K
Tamminga
C A
CA
Chase
T N
TN
Nilaver
G
G
D000818:Animals; D001058:Apomorphine / Q000037:antagonists & inhibitors; D001549:Benzamides / Q000494:pharmacology; D018492:Dopamine Antagonists; D007163:Immunosorbent Techniques; D007276:Injections, Intraventricular; D008297:Male; D011377:Proglumide / Q000494:pharmacology; D011388:Prolactin / Q000097:blood*; D051381:Rats; D011919:Rats, Inbred Strains; D012844:Sincalide / Q000008:administration & dosage / Q000494:pharmacology*; D014660:Vasoactive Intestinal Peptide / Q000502:physiology*
D001549:Benzamides; D018492:Dopamine Antagonists; D014660:Vasoactive Intestinal Peptide; D011388:Prolactin; D011377:Proglumide; C013841:benzotript; D012844:Sincalide; D001058:Apomorphine