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Updated: Aug 24, 2026

In vitro Measurements of Tracheal Constriction Using Mice
Published on: June 25, 2012
cAMP-independent mechanism is significantly involved in beta2-adrenoceptor-mediated tracheal relaxation
Katsuo Koike1, Yoko Yamashita, Takahiro Horinouchi
1Department of Chemical Pharmacology, Toho University School of Pharmaceutical Sciences, Miyama 2-2-1, Funabashi City, Chiba 274-8510, Japan.
Abstract:
The role of cAMP in the beta2-adrenoceptor-mediated relaxation in response to salbutamol was examined in guinea pig tracheal smooth muscle. The concentration-dependent salbutamol-induced relaxation was antagonized in a competitive fashion by a beta2-selective adrenoceptor antagonist, butoxamine, with a pA2 value of 6.90. Salbutamol (10 microM) elevated the tracheal smooth muscle cAMP content by about fivefold, a response which was significantly inhibited by an adenylyl cyclase inhibitor, 9-(tetrahydro-2-furanyl)-9H-purin-6-amine (SQ 22,536, 100 microM). However, the salbutamol-elicited relaxation was not diminished by SQ 22,536 (100 microM). These results provide evidence for the first time that a cAMP-independent mechanism(s) is involved in beta2-adrenoceptor-mediated tracheal smooth muscle relaxation in the guinea pig.
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