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. 1995 Jan;114(1):73–76. doi: 10.1111/j.1476-5381.1995.tb14907.x

An enhancing effect of 5-hydroxytryptamine on electrically evoked atropine-resistant contraction of guinea-pig proximal colon.

S Kojima 1, Y Shimo 1
PMCID: PMC1510169  PMID: 7712032

Abstract

1. In the presence of atropine (0.2 microM) and indomethacin (2 microM), the effects of 5-hydroxytryptamine (5-HT) have been studied on electrically-evoked, neurogenic contractions of the guinea-pig proximal colon in vitro. 2. 5-HT, at higher concentrations than 1 nM, caused an increase in electrically (1 Hz, 0.3 ms, 160 mA)-evoked, atropine-resistant contractions in a concentration-dependent manner and at 30 nM produced a maximal effect (pEC50 value of 8.20 +/- 0.11, n = 6). The enhancing effects of 5-HT on the electrically evoked contractions were mimicked by alpha-methyl-5-HT (pEC50 value of 6.59 +/- 0.05, n = 6). 3. Both hexamethonium (100 microM) and spantide (10 microM), selective antagonists for nicotinic and tachykinin receptors respectively, significantly reduced the enhancement of the electrically evoked contractions by 5-HT (30 nM). 4. DAU 6285 (3 microM), a 5-HT4 receptor antagonist, abolished the enhancing action of 5-HT (30 nM), but metitepine (0.03 microM), a 5-HT1/5-HT2 receptor antagonist, ketanserin (0.01 microM), a 5-HT2 receptor antagonist, and ondansetron (1 microM), a 5-HT3 receptor antagonist, had no effect on the enhancement. The enhancing effects of alpha-methyl-5-HT (1 microM) were also abolished by DAU 6285 (3 microM). 5. Both 5-HT (30 nM) and alpha-methyl-5-HT (1 microM) had no effect on contractions to exogenous substance P (0.15-0.3 nM).(ABSTRACT TRUNCATED AT 250 WORDS)

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Selected References

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