Receptor-linked cyclic amp systems in rat neostriatum: Differential localization revealed by kainic acid injection

Abstract

Various receptor-linked cyclic AMP systems were measured in rat neostriatum 2–14 days after selective destruction of neuronal cell bodies and dendrites by microinjection of 3 μg of kainic acid. Basal adenylate cyclase activity was reduced by up to 56% in the injected side and the sensitivity to dopamine was abolished. Up to 84% of cyclic nucleotide phosphodiesterase activity, hydrolyzing either cyclic AMP or cyclic GMP, was destroyed by kainic acid injection. Specific binding of [ 3H]etorphine and [ 3H]spiroperidol was reduced by up to 62% in the injected side, while non-specific binding was unchanged. All of these changes were time-dependent, and were greatest 7–14 days after kainic acid treatment. On the other hand, intrastriatal kainic acid injection caused no change in the steady-state concentration of cyclic AMP in striatal slices, or in the in vivo cyclic AMP content in the striatum of rats killed by microwave irradiation. Receptor-mediated increases in cyclic AMP accumulation in striatal slices were either unchanged or markedly potentiated by kainic acid treatment. The maximum response to adenosine was unchanged, while the response to isoprenaline was increased up to 3.7-fold, the response to dopamine increased up to 6.7-fold, and the response to PGE 1 increased up to 30-fold. The effect of dopamine in kainic acid-treated striatal slices was no longer blocked by fluphenazine, but was blocked by propranolol, suggesting an interaction of dopamine with a β-adrenoceptor in kainic acid-treated slices. The results suggest differential cellular localizations of the various receptor-linked cyclic AMP systems in rat neostriatum. Some dopamine and opiate receptors, as well as most of the phosphodiesterase activity, are associated with local neuronal elements, while β-adrenoceptor, adenosine and PGE 1 alterations in cyclic AMP are not. The potentiation of the β-adrenoceptor and PGE 1 responses suggests that they may occur in glial cells. In addition, the pool of adenylate cyclase destroyed by kainic acid appears to make little contribution to normal levels of cyclic AMP in the tissue.