D2-like receptors mediate the expulsion phase of ejaculation elicited by 8-hydroxy-2-(di-N-propylamino)tetralin in rats.
The mechanism of action by which 8-hydroxy-2-(di-N-propylamino)tetralin (8-OH-DPAT) facilitates ejaculation in conscious rats is not clearly established. The serotonin (5-HT) 1A agonist 8-OH-DPAT may actually act on cerebral dopaminergic receptors to exert its proejaculatory effect. The present work was undertaken to clarify this issue by testing various compounds i.c.v. delivered in an experimental model of the expulsion phase of ejaculation in anesthetized Wistar rats. Intracerebroventricular delivery of 8-OH-DPAT dose-dependently (ED(50) = 17 microg) induced rhythmic contractions of bulbospongiosus (BS) muscles, which are of paramount importance for the expulsion of semen, occurring in the form of cluster of bursts evidenced by the recording of BS muscle electrical activity. The 5-HT1A antagonist WAY100635 (N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinylcyclohexanecarboxamide) (20 microg) i.c.v. coadministered with 8-OH-DPAT (20 microg) was unable to inhibit the effect of 8-OH-DPAT on BS muscle contractile activity. Conversely, raclopride (40 microg) and spiperone (10 microg), both dopamine D2-like receptor antagonists, i.c.v. coinjected with 8-OH-DPAT (20 microg), abolished BS muscle contractions. The involvement of D2-like receptors was further supported by the fact that the D2-like agonist quinelorane (20 microg i.c.v.) also induced BS muscle rhythmic contractions. Our data demonstrate that D2-like receptors mediate the induction by 8-OH-DPAT of rhythmic BS muscle contractions and suggest that i.c.v. delivery of D2-like receptor agonists to anesthetized rats represents a relevant experimental model to study the expulsion phase of ejaculation.
Clément
Pierre
P
Pelvipharm Laboratories, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France.
Bernabé
Jacques
J
Kia
Hosein Kami
HK
Alexandre
Laurent
L
Giuliano
François
F
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004542:Ejaculation / Q000187:drug effects*; D007276:Injections, Intraventricular; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D017448:Receptors, Dopamine D2 / Q000378:metabolism / Q000502:physiology*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*
D017448:Receptors, Dopamine D2; D017366:Serotonin Receptor Agonists; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin