STIMULATION OF GLYCOGENOLYSIS IN RAT CAUDATE NUCLEUS SLICES BY L‐ISOPROPYLNOREPINEPHERINE, DIBUTYRYL CYCLIC AMP AND 2‐CHLOROADENOSINE

Abstract

Abstract—Dopamine (DA), L‐isópropylnorepinepherine (IPNE), 2‐chloroadenosine (2‐Cl‐Ado), 3‐isobutyl, I‐methylxanthine (IBMX) and N6,O2′‐dibutyryl cyclic AMP have been investigated for their effects on glycogen levels in rat caudate nucleus slices. Incubation of slices with 1 mM‐dibutyryl cyclic AMP, or with 50 μM‐IPNE in the presence of 1mM‐IBMX, or with 5‐500 μM‐2‐Cl‐Ado reduced glycogen levels to about 50% of control. Incubation of slices with 1 mM‐IBMX alone, or with 50μM‐IPNE alone, or with 50μM‐DA either alone or in the presence of 1 mM‐IBMX was without significant effect on glycogen levels. The effect of IPNE + IBMX was completely abolished by the prior addition of 10 μM‐propranolol. The effect of 10 μM‐2‐Cl‐Ado was not effectively prevented by either 100 μM‐theophylline or 100 μM‐cordycepin. The results indicate that the β‐adrenergic adenylate cyclase in the rat caudate nucleus plays a role in the regulation of glycogen metabolism, while the DA‐stimulated adenylate cyclase is not significantly involved. The 2‐Cl‐Ado‐stimulated adenylate cyclase may be involved in the control of glycogen metabolism, but other mechanisms for the 2‐CI‐Ado action, such as interference with allosteric regulatory sites on glycogen phosphorylase, have not been ruled out.