The 5HT2C Receptor Can Modulate Cyclic Adenosine Monophosphate AMP Accumulation

When expressed at high density (12 pmol/mg membrane protein) in stably transformed AV12 cells, the 5-HT2C receptor has been shown to inhibit forskolin-stimulated cAMP production with an IC50 ยป 50 nmol/L. This effect was sensitive to PTX, suggesting the involvement of Gm/o proteins. In contrast, the 5-HT2A and 5-HT2B receptors expressed at similar levels did not decrease adenylate cyclase (AC) activity in those cells, although all three receptor subtypes were coupled to PLC activation. Pretreatment of the cells expressing high levels of 5-HT2C receptor with PTX also unmasked a small stimulatory effect of the 5-HT2C receptor on cAMP accumulation. When expressed at low density (~150 fmol/mg of membrane protein), the 5-HT2C receptor could increase forskolin-stimulated cAMP production by twofold (Lucaites et al. 1996).

These results demonstrate that 5-HT2C receptor density may determine the signaling pathway(s) to which the receptor couples. At the same time, the 5-HT2C receptor endogenously expressed in pig choroids plexus has not been linked either to stimulation of AC or to inhibition of forskolin-stimulated cyclase activity (Palacios et al. 1986). Thus, it is not clear whether the 5-HT2C receptor can modulate cAMP levels in native tissues.

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Defeat Drugs and Live Free

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