Dependence of -adrenoceptor mediated mechanical effects on the glycogen concentration in the rabbit isolated small intestine.

In the rabbit isolated intestine, tachyphylaxis was evident in the inhibitory responses to isoprenaline, but not in those to phenylephrine, ATP or dibutyryl cyclic AMP. The tachyphylaxis to isoprenaline was associated with a spontaneous fall in the tissue glycogen concentration and was enhanced when the glycogen concentration was markedly reduced by incubation of the tissue under anaerobic conditions in glucose-free Krebs solution. Doubling the glucose concentration of the Krebs solution slowly restored the response to isoprenaline and prevented the development of tachyphylaxis to it. The results support the concept that the beta-adrenoceptor mediated response is dependent on some product of cellular metabolism.