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

Dopamine (DA), L-isópropylnorepinepherine (IPNE), 2-chloroadenosine (2-Cl-Ado), 3-isobutyl, I-methylxanthine (IBMX) and N⁶,O^2′-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.