CULTURED ASTROCYTES EXPRESS MESSENGER-RNA FOR MULTIPLE SEROTONIN RECEPTOR SUBTYPES, WITHOUT FUNCTIONAL COUPLING OF 5-HT1 RECEPTOR SUBTYPES TO ADENYLYL-CYCLASE

The literature describing the expression of 5-HT receptor subtypes by astrocytes is controversial and incomplete. It is clear that primary c ultures of astrocytes express receptors of the 5-HT2 family coupled to phospholipase C and of the 5-HT7 receptor family positively coupled t o adenylyl cyclase. Cultured astrocytes have also been reported to exp ress receptors of the 5-HT1 family, although the exact subtypes presen t are unknown. In the present study we have investigated which of the known rat C-protein coupled 5-HT receptor mRNAs are expressed by cultu red astrocytes. Reverse transcriptase-polymerase chain reaction (RT-PC R) revealed expression of 5-HT1A, 5-HT1B, 5-HT1D, 5-HT1F, 5-HT2A, 5-HT 2B, 5-HT2C, 5-HT5B, 5-HT6 and 5-HT7 receptor mRNAs in astrocytes deriv ed from 2-day old rats and cultured for 10-12 days. Messenger RNAs for 5-HT4 and 5-HT5A receptors were not detected. The functional expressi on of 5-HT1 receptor subtypes was investigated by measuring the abilit y of 5-HT1 receptor agonists: B-OH-DPAT (5-HT1A receptors), RU24969 (5 -HT1A, 5-HT1B, 5-HT1D, and 5-HT1F receptors) or sumatriptan (5-HT1B, 5 -HT1D, and 5-HT1F receptors) to modulate forskolin or isoproterenol st imulated cAMP production. These compounds, at concentrations up to 10 mu M, did not significantly attenuate cAMP production. These results i ndicate that although astrocytes express mRNA for each of the five 5-H T1 receptor subtypes which have been isolated from the rat, these rece ptors are not coupled to the inhibition of adenylyl cyclase. (C) 1998 Elsevier Science B.V. All rights reserved.