Pharmacological and Molecular Evidence for Dopamine D1 Receptor Expression by Striatal Astrocytes in Culture

The neurotransmitter dopamine (DA) at a 10 ?M concentration elicited a stimulation of intracellular cyclic AMP (cAMP) accumulation in cultured astro- cytes derived from embryonic rat striatum. This accumulation was partially blocked by the ?-adrener- gic receptors antagonist propranolol, mimicked by the D1 agonist SKF 38393 and by the mixed D1/D2 agonist apomorphine. A regional heterogeneity in the magni- tude of dopamine-induced cAMP accumulation was observed in cultured astrocytes obtained from differ- ent brain areas. The maximum effect was observed in striatal astrocytes, a lower effect in cortical astrocytes, and no increase was detected in cerebellar astrocytes. Reverse transcription-polymerase chain reaction (RT-PCR) coupled to Southern blot hybridization demonstrated that striatal astrocytes express only D1 receptor mRNA and Western blot analysis confirmed the expression of the D1 receptor protein in striatal astrocytes. In contrast to what found in neurons, the D1-dependent cAMP formation in striatal astrocytes is partially reduced by pertussis toxin (PTX) treatment. The stimulation of D1 receptors or the activation of adenylyl cyclase by forskolin led to an increase of cytosolic and nuclear protein kinase A (PKA) catalytic activity. The presence of dopamine D1 receptors in cultured striatal astrocytes suggests a role of dopa- mine in the regulation of cellular processes in striatal astrocytes. J. Neurosci. Res. 58:544-552, 1999.