Stimulation of 5-HT₂Receptors in Prefrontal Pyramidal Neurons Inhibits Ca_v1.2 L-Type Ca²⁺Currents Via a PLCβ/IP3/Calcineurin Signaling Cascade

Abstract

There is growing evidence linking alterations in serotonergic signaling in the prefrontal cortex to the etiology of schizophrenia. Prefrontal pyramidal neurons are richly innervated by serotonergic fibers and express high levels of serotonergic 5-HT(2)-class receptors. It is unclear, however, how activation of these receptors modulates cellular activity. To help fill this gap, whole cell voltage-clamp and single-cell RT-PCR studies of acutely isolated layer V-VI prefrontal pyramidal neurons were undertaken. The vast majority (>80%) of these neurons had detectable levels of 5-HT(2A) or 5-HT(2C) receptor mRNA. Bath application of 5-HT(2) agonists inhibited voltage-dependent Ca(2+) channel currents. L-type Ca(2+) channels were a particularly prominent target of this signaling pathway. The L-type channel modulation was blocked by disruption of G(alphaq) signaling or by inhibition of phospholipase Cbeta. Antagonism of intracellular inositol trisphosphate signaling, chelation of intracellular Ca(2+), or depletion of intracellular Ca(2+) stores also blocked this modulation. Inhibition of the Ca(2+)-dependent phosphatase calcineurin prevented receptor-mediated modulation of L-type currents. Last, the 5-HT(2) receptor modulation was robustly expressed in neurons from Ca(v)1.3 knockout mice. These findings argue that 5-HT(2) receptors couple through G(alphaq) proteins to trigger a phospholipase Cbeta/inositol trisphosphate signaling cascade resulting in the mobilization of intracellular Ca(2+), activation of calcineurin, and inhibition of Ca(v)1.2 L-type Ca(2+) currents. This modulation and its blockade by atypical neuroleptics could have wide-ranging effects on synaptic integration and long-term gene expression in deep-layer prefrontal pyramidal neurons.

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Evidence for association of schizophrenia with genetic variation in the 8p21.3 gene,PPP3CC, encoding the calcineurin gamma subunit

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