Serotonin induces a biphasic response in rabbit cavernosal smooth muscle: relevance to the erectile process.
BACKGROUND
Serotonin (5-hydroxytryptamine; 5-HT) can cause contraction in cavernosal smooth muscle. We further evaluated this effect of 5-HT.


METHODS
Organ bath studies were used.


RESULTS
5-HT induced a sustained contraction occasionally accompanied by a transient relaxation (in 30% of rabbit cavernosal tissues) that preceded the contraction. Ondansetron and Y-25130 (both 5-HT3 receptor antagonists) but not SB-269970 (a 5-HT7 receptor antagonist) significantly inhibited or abolished this transient relaxation. Doxazosin (dox, an alpha1-receptor antagonist) and ketanserin (ketan, a 5-HT2A receptor antagonist) significantly inhibited or abolished the sustained contraction. The effects of dox on 5-HT-mediated contraction were concentration-dependent.


CONCLUSIONS
Our findings further confirm that the peripheral serotonergic pathway may play a part in the erectile process via 5-HT2A receptor-mediated contractile and 5-HT3 receptor-mediated relaxant activities. Our results also support the findings of human studies, which suggest that both ketan and dox may exert beneficial effects on the erectile process.
Lau
David H W
DH
Department of Urology, Royal Free Hospital and University College Medical School, University College London, London, UK.
Thompson
Cecil S
CS
Mumtaz
Faiz H
FH
Morgan
Robert J
RJ
Mikhailidis
Dimitri P
DP
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D010410:Penile Erection / Q000187:drug effects; D010413:Penis / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D011817:Rabbits; D044402:Receptor, Serotonin, 5-HT2A / Q000378:metabolism*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000378:metabolism; D044406:Receptors, Serotonin, 5-HT3 / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism*; D058830:Serotonin 5-HT2 Receptor Antagonists; D058831:Serotonin 5-HT3 Receptor Antagonists; D012702:Serotonin Antagonists / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D004791:Enzyme Inhibitors; D044402:Receptor, Serotonin, 5-HT2A; D011942:Receptors, Adrenergic, alpha; D044406:Receptors, Serotonin, 5-HT3; D058830:Serotonin 5-HT2 Receptor Antagonists; D058831:Serotonin 5-HT3 Receptor Antagonists; D012702:Serotonin Antagonists; D012701:Serotonin; D019001:Nitric Oxide Synthase