Facilitation and inhibition of male rat ejaculatory behaviour by the respective 5-HT1A and 5-HT1B receptor agonists 8-OH-DPAT and anpirtoline, as evidenced by use of the corresponding new and selective receptor antagonists NAD-299 and NAS-181.
1. Ejaculatory problems and anorgasmia are well-known side-effects of the SSRI antidepressants, and a pharmacologically induced increase in serotonergic neurotransmission inhibits ejaculatory behaviour in the rat. In the present study the role of 5-HT1A and 5-HT1B receptors in the mediation of male rat ejaculatory behaviour was examined by use of selective agonists and antagonists acting at these 5-HT receptor subtypes. 2. The 5-HT1A receptor agonist 8-OH-DPAT (0.25-4.00 micromol kg(-1) s.c.) produced an expected facilitation of the male rat ejaculatory behaviour, and this effect was fully antagonized by pretreatment with the new selective 5-HT1A receptor antagonist (R)-3-N,N-dicyclobutylamino-8-fluoro-3,4-dihydro-2H-1-benzopyran-5 -carboxamide hydrogen (2R,3R) tartrate monohydrate (NAD-299) (1.0 micromol kg(-1) s.c.). NAD-299 by itself (0.75-3.00 micromol kg(-1) s.c.) did not affect the male rat ejaculatory behaviour. 3. The 5-HT1B receptor agonist anpirtoline (0.25-4.00 micromol kg(-1) s.c.) produced a dose-dependent inhibition of the male rat ejaculatory behaviour, and this effect was fully antagonized by pretreatment with the 5-HT1B receptor antagonist isamoltane (16 micromol kg(-1) s.c.) as well as by the new and selective antagonist (R)-(+)-2-(3-morpholinomethyl-2H-chromene-8-yl)oxymethylmorphol  ino methansulphonate (NAS-181) (16 micromol kg(-1) s.c.). Isamoltane (1.0-16.0 micromol kg(-1) s.c.) and NAD-181 (1.0-16.0 micromol kg(-1) s.c.) had no, or weakly facilitatory effects on the male rat ejaculatory behaviour. The non-selective 5-HT1 receptor antagonist (-)-pindolol (8 micromol kg(-1) s.c.), did not antagonize the inhibition produced by anpirtoline. 4. The present results demonstrate opposite effects, facilitation and inhibition, of male rat ejaculatory behaviour by stimulation of 5-HT1A and 5-HT1B receptors, respectively, suggesting that the SSRI-induced inhibition of male ejaculatory dysfunction is due to 5-HT1B receptor stimulation.
Hillegaart
V
V
Department of Pharmacology, Astra Arcus AB, Södertälje, Sweden. viveka.hillegaart@fyfa.ki.se
Ahlenius
S
S
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001578:Benzopyrans / Q000494:pharmacology; D004542:Ejaculation / Q000187:drug effects*; D005260:Female; D008297:Male; D009025:Morpholines / Q000494:pharmacology; D010869:Pindolol / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D011412:Propanolamines / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D044302:Receptor, Serotonin, 5-HT1B; D011985:Receptors, Serotonin / Q000187:drug effects; D044263:Receptors, Serotonin, 5-HT1; D018490:Serotonin Agents / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D012726:Sexual Behavior, Animal / Q000187:drug effects*; D013997:Time Factors
C112429:2-(((3-(morpholinylmethyl)-2H-chromen-8-yl)oxy)methyl)morpholine; D000319:Adrenergic beta-Antagonists; D001578:Benzopyrans; D009025:Morpholines; D010880:Piperidines; D011412:Propanolamines; D011725:Pyridines; D044302:Receptor, Serotonin, 5-HT1B; D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D018490:Serotonin Agents; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; C075631:anpirtoline; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; C058392:isamoltane; D010869:Pindolol; C108607:robalzotan