The Adrenergic Receptors in Isolated Rabbit Stomach Muscle

The effects of stimulation of the adrenergic α‐ and β‐receptors in muscle from the antrum and fundus of the rabbit stomach have been studied. The muscular activity was markedly different in preparations from the two parts. In the muscle from the antrum rhythmic contractions generally occurred, while alterations in the tone were small and infrequent. In the muscle from the fundus, rhythmic contractions were rarely seen, but considerable variations in tone occurred in response to drugs. β‐receptor stimulation invariably gave inhibitory effects, but the effect of α‐receptor stimulation in longitudinal and circular antrum strips, and in longitudinal fundus strips, depended on the existing muscular activity when the drug was added, high activity favouring inhibitory effects and low activity favouring excitatory effects. In a few antrum strips low concentrations of α‐adrenergic agents increased the frequency of the rhythmic contractions while higher concentrations inhibited them. In circular strips from the fundus α‐receptor stimulation gave only excitatory responses. The effect of the adrenergic agents were apparently due to a direct influence on the muscle, as the quality of the responses was unaffected by pretreatment with atropine, hexamethonium and tetrodotoxin, by the presence or absence of mucosa, or by cold storage for 24 hours.