Background: Toddalia asiatica of Rutaceae, a Taiwan folk medicine, is used as an analgesic and anti-inflammatory herb. Cyclohexylamine (CHA) is an active compound from T. asiatica. Previous reports indicate CHA contracts rat vas deferens. However, the contractile mechanism of CHA on rat vas deferens was not yet reported. The purpose of this study was to investigate the contractile mechanism of CHA on rat epididymal portion of vas deferens.

Methods: Male S.D. rats weighting between 200 g to 250 g were used. The epididymal portion of vas deferens was isolated and was added with various concentrations of serotonin, serotonin antagonists and CHA.

Results: Serotonin elicited dose-dependent (1x10-7M~1x10-4M) contractions on rat epididymal vas deferens, which were inhibited by pretreatment with ketanserin (1 x 10-8 M ~ 1 x 10-6 M), methysergide (1 x 10-5 M) and propranolol (1 x 10-4 M), respectively. CHA elicited dose-dependent (1x10-8M~1x10-4M) contractions on rat epididymal vas deferens. The contractions of CHA (1x10-4M) on epididymal vas deferens were enhanced by serotonin in a dose-dependent manner. Methysergide (1 x 10-7 ~1 x 10-5 M) did not affect the contractions evoked by CHA. However, the CHA elicited contraction was almost completely inhibited by ketanserin (1 x 10-5 M) and was enhanced by propranolol. The effect of propranolol at the concentration of 1 x 10-4 M on CHA was likely as CHA at high concentration alone.

Conclusions: From the above results, the contraction evoked by CHA on the isolated rat epididymal vas deferens might be mediated by serotonergic receptors, primary through 5-HT2A subtype.

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