Alpha-methyl-5-HT, a 5-HT2 receptor agonist, stimulates beta2-adrenoceptors in guinea pig airway smooth muscle.
Pharmacol Res
; 54(6): 468-73, 2006 Dec.
Article
in En
| MEDLINE
| ID: mdl-17079161
ABSTRACT
Alpha-methyl-5-HT is widely used as a high-affinity 5-HT(2) receptors agonist, though some studies have postulated that this drug also activates other serotonergic receptors. In the present work, we found that a wide range of concentrations of alpha-methyl-5-HT induced biphasic responses (contraction followed by relaxation) in guinea pig tracheal rings. The relaxing phase caused by 32microM alpha-methyl-5-HT was blocked by 0.1microM propranolol. Furthermore, during an ongoing histamine-induced contraction, alpha-methyl-5-HT (0.1-100microM) produced a concentration-dependent relaxation starting at 10microM. This relaxation was fully abolished by 0.1microM propranolol or 1microM ICI 118,551 (a selective beta(2)-adrenoceptor antagonist). Additionally, in electrophysiological recordings, 32microM alpha-methyl-5-HT also enhanced the membrane K(+) currents of single tracheal myocytes, an effect reverted by propranolol and ICI 118,551, and mimicked by 0.1microM salbutamol. Thus, we concluded that alpha-methyl-5-HT activates beta(2)-adrenoceptors in guinea pig tracheal smooth muscle at concentrations >or=10microM. This effect must be taken into account when this drug is used in airway smooth muscle and in other tissues expressing beta(2)-adrenoceptors.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Serotonin
/
Receptors, Serotonin
/
Serotonin Receptor Agonists
/
Receptors, Adrenergic, beta-2
/
Muscle, Smooth
Limits:
Animals
Language:
En
Journal:
Pharmacol Res
Journal subject:
FARMACOLOGIA
Year:
2006
Document type:
Article
Affiliation country:
Mexico