British journal of pharmacology
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1. GABAB agonists inhibit neuronal processes which are important in the pathogenesis of airway disease, such as bronchospasm. Cough is a prominent symptom of pulmonary disease, but the effects of GABAB agonists on this airway reflex are unknown. ⋯ In this model, baclofen (ED50 = 0.63 mg kg-1) was less potent than either codeine or dextromethorphan. The antitussive effect of baclofen in the cat was antagonized by the GABAB antagonists, CGP 35348 (10 mg kg-1, i.v.) and 3-aminopropylphosphonic acid (3 mg kg-1, i.v.).6. We show that baclofen and 3-APPi have antitussive effects in the guinea-pig and cat and these effects are mediated by GABAB receptors.
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1. The formation of adenosine 3':5'-cyclic monophosphate (cyclic AMP) and inositol(1,4,5)trisphosphate (Ins(1,4,5)P3), induced by ATP and other nucleotides was investigated in mouse C2C12 myotubes. 2. ATP (100 microM) and ATP gamma S (100 microM) caused a sustained increase in cyclic AMP content of the cells, reaching a maximum after 10 min. ⋯ In contrast, UTP (30 microM-I mM) enhanced adenosine-induced cyclic AMP formation.8. Adenosine-sensitive P1-purinoceptors activating cyclic AMP formation were found in C2C12 myotubes. Further, a novel P2-purinoceptor is postulated, sensitive to ATP, ADP and ATPgammaS, which also activates the formation of cyclic AMP in C2C12 myotubes.
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1. In vascular smooth muscle, alpha 1-adrenoceptors have been classified recently into two or three subtypes. We examined which alpha 1-adrenoceptor subtypes are involved in the noradrenaline-induced contraction of rat portal vein smooth muscle. 2. ⋯ The present results indicate the existence of two distinct o1-adrenoceptor subtypes in rat portal vein smooth muscle, which show high- and low-affinities respectively for each of prazosin, WB4101 andHV723 and correspond to alphalH- and alphalL-adrenoceptor subtypes. According to recent alpha1-adrenoceptor subclassifications, the alpha l H-adrenoceptor subtype which is sensitive to inactivation by CEC may correspond to the alpha1B-adrenoceptor subtype. The contraction induced by noradrenaline seems to be predominantly mediated through the alphalL-adrenoceptor subtypes which may include the alpha1N-adrenoceptor subtype, as recently proposed.