The 5-hydroxytryptamine (5-HT)1A receptor system plays a prominent role in a variety of physiological functions and behaviors and regulation of the responsiveness of this receptor system has been implicated in the therapeutic mechanism of action of the selective serotonin reuptake inhibitor class of antidepressant drugs. Here we report that the responsiveness of the 5-HT1A receptor system is regulated by consequences of activation of the phospholipase A2 (PLA2) and phospholipase C effector pathways. In Chinese hamster ovary cells stably expressing the human 5-HT1A receptor, 5-HT1A receptor-mediated inhibition of forskolin-stimulated cAMP accumulation was reduced by a cyclooxygenase-dependent arachidonic acid (AA) metabolite produced in response to exogenously applied AA or activation of PLA2 directly with melittin or indirectly by receptor activation. This effect of the AA metabolite was sensitive to the activation state of adenylyl cyclase suggesting that the target of the AA metabolite-induced reduction in 5-HT1A responsiveness was adenylyl cyclase. Activation of protein kinase C with a phorbol ester also reduced 5-HT1A receptor function. In contrast, increases in intracellular calcium levels via a calcium ionophore or thapsigargin enhanced 5-HT1A responsiveness. The net effect of activation of phospholipid-coupled receptors on 5-HT1A agonist efficacy depended upon the relative capacity to produce these positive (calcium) and negative (AA) regulators. These data demonstrate that the responsiveness of the 5-HT1A receptor system can be enhanced or depressed by consequences of activation of phospholipid-coupled receptor systems. An understanding of the cellular mechanisms for regulation of 5-HT1A function may lead to novel targets for development of psychotherapeutic drugs.
|Original language||English (US)|
|Number of pages||11|
|Journal||Journal of Pharmacology and Experimental Therapeutics|
|State||Published - Jun 2001|
ASJC Scopus subject areas
- Molecular Medicine