Receptors mediating the actions of 5-hydroxytryptamine on the isolated retractor muscle of the penis preparations from Archachatina marginata (Swainson).
1. The effects of some 5-hydroxytryptamine (5-HT) receptor agonist and antagonists on the isolated retractor muscle of the penis of Archachatina marginata were investigated. 2. Both 5-hydroxytryptamine and lysergic acid diethylamide (LSD) contracted the preparations. The mean pD2 values obtained for 5-HT and LSD were 5.26 +/- 0.21 (N = 10) and 6.3 +/- 0.36 (N = 8) respectively. 3. 5-Methoxy, N,N,-dimethyltryptamine (5-MeODMT; N = 6) trifluoromethylphenylpiperazine (TFMPP; N = 6) alpha-methyl 5-hydroxytryptamine (alpha-Me-5-HT); N = 6) and both L and DL-5-hydroxytryptophan (L-5-HTP; N = 6, DL-5-HTP; N = 6) did not contract the preparations even when concentrations up to 10(-4) M were administered. 4. Ketanserin (10(-8)-10(-6) M) produced rightward shift of the concentration-response curve of 5-HT. (pA2 = 8.0 +/- 0.25, slope = 0.34 +/- 0.03; N = 6). 5. The contractions of the RMP to 5-HT were not antagonised by either LY53857 or ICS 205-930. 6. The present study does not reveal the presence of 5-HT1-like or 5HT2 receptors on the RMP. However 5-HT3 receptors do not seem to exist on this invertebrate smooth muscle.
Department of Pharmacology, College of Health Sciences, University of Port Harcourt, Nigeria.
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Innocent
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Olufemi
D000818:Animals; D004873:Ergolines / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D007650:Ketanserin / Q000494:pharmacology; D008238:Lysergic Acid Diethylamide / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009132:Muscles / Q000187:drug effects / Q000502:physiology*; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D012908:Snails / Q000187:drug effects / Q000502:physiology*; D000077526:Tropisetron
D004873:Ergolines; D007211:Indoles; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D012701:Serotonin; D000077526:Tropisetron; D008238:Lysergic Acid Diethylamide; D007650:Ketanserin; C032663:LY 53857