Aug 1, 1987

Mechanical and electrical responses to alpha-adrenoceptor activation in the circular muscle of guinea-pig stomach

British Journal of Pharmacology
S Chihara, T Tomita


1 In the circular muscle of the corpus region of the guinea-pig stomach, the effects of catecholamines on mechanical activity were studied with simultaneous recording of membrane potential by use of intracellular microelectrodes. In order to investigate responses mediated through alpha-adrenoceptors, the beta-adrenoceptors were blocked by propranolol (10(-6) M) in most experiments. 2 Adrenaline (less than 10(-6) M) produced a monophasic contraction with little change in membrane potential. At higher concentrations (greater than 10(-5) M), adrenaline usually produced an early transient contraction followed by a slow tonic contraction. During the early phase, the membrane was hyperpolarized and slow waves were reduced in amplitude. 3 The phasic contractions superimposed on the late slow phase of the contractile response were higher in frequency and larger in amplitude than in controls before adrenaline application. These changes were associated with an increase in the amplitude and frequency of slow waves, and with a spike-like component appearing on the top of each slow wave. 4 Adrenaline-induced changes in mechanical and electrical activity were inhibited by prazosin, but largely unaffected by yohimbine. In some preparations, t...Continue Reading

Mentioned in this Paper

Yohimbin Spiegel
Resting Potentials
Catecholamines Measurement
Contraction (Finding)
Smooth Muscle
Electrical Activity of Brain
Adrenergic alpha-Agonists
Epinephrine Measurement

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