Pharmacological and molecular evidence for dopamine D1 receptor expression by striatal astrocytes in culture

The neurotransmitter dopamine (DA) at a 10 mu M concentration elicited a stimulation of intracellular cyclic AMP (cAMP) accumulation in cultured astrocytes derived from embryonic rat striatum. This accumulation was partially blocked by the beta-adrenergic receptors antagonist propranolol, mimicked by the D-1 agonist SKF 38393 and by the mixed D-1/D-2 agonist apomorphine. A regional heterogeneity in the magnitude of dopamine-induced cAMP accumulation was observed in cultured astrocytes obtained from different 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 D-1 receptor mRNA and Western blot analysis confirmed the expression of the D-1 receptor protein in striatal astrocytes, In contrast to what found in neurons, the D-1-dependent cAMP formation ia striatal astrocytes is partially reduced by pertussis toxin (PTX) treatment, The stimulation of D-1 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 D-1 receptors in cultured striatal astrocytes suggests a role of dopamine in the regulation of cellular processes in striatal astrocytes. J. Neurosci. Res. 58:544-552, 1999. (C) 1999 Wiley-Liss, Inc.