5-Hydroxytryptamine(2B) receptors stimulate Ca2+ increases in cultured astrocytes from three different brain regions

The expression of 5-hydroxytryptamine-2B (5-HT2B) receptor mRNA has recentl y been shown in cultured astrocytes. Here the expression of Functional 5-HT 2B receptors has been studied in cultured astrocytes from rat cerebral cort ex, hippocampus, and brain stem. Fluo-3- and fura-2-based microspectrofluor ometry was used for measuring changes in intracellular free calcium concent rations ([Ca2+](i)). The 5-HT2B agonist alpha-methyl 5-HT (40 nM) produced rapid transient increases in [Ca2+](i) in astrocytes from all three brain r egions studied, and these responses were blocked by the selective 5-HT2B an tagonist rauwolscine (1 mu M). The specificity of the responses to alpha-me thyl 5-HT was further demonstrated by the failure of 4-(4-fluorobenzoyl)-1- (4-phenylbutyl)-piperidine oxalate (1 mu M), a specific 5-HT2A/5-HT2C antag onist, to block these responses. The 5-HT2B-induced increases in [Ca2+](i) persisted in Ca2+-free buffer, indicating that the increase in [Ca2+](i) re sults from mobilization of intracellular Ca2+ stores. The expression of 5-H T2B receptors on astroglial cells was further verified immunohistochemicall y and by Western blot analysis. These results provide evidence of the exist ence of 5-HT2B receptors on astrocytes in primary culture. (C) 2000 Publish ed by Elsevier Science Ltd. All rights reserved.