STIMULATION OF α1-ADRENOCEPTORS FACILITATES GABAergic TRANSMISSION ONTO PYRAMIDAL NEURONS IN THE MEDIAL PREFRONTAL CORTEX

Whereas activation of alpha(1)-adrenoceptors (alpha(1)-ARs) modulates glutamatergic transmission, the roles of alpha(1)-ARs in GABAergic transmission in the medial prefrontal cortex (mPFC) are elusive. Here, we examined the effects of the alpha(1)-AR agonist phenylephrine (Phe) on GABAergic transmission onto pyramidal neurons in the deep layers of the mPFC. We found that bath application of Phe dose-dependently increased the amplitude of evoked IPSCs (eIPSCs). Phe increased the frequency but not the amplitude of miniature IPSCs (mIPSCs). Ca2+ influx through T-type voltage-gated calcium channels is required for Phe-induced increases in GABA release. Phe increases GABA release probability and the number of releasable vesicles. Phe depolarizes the fast-spiking (FS) interneurons without effects on the firing rate of action potentials (APs) of interneurons. Phe-induced depolarization is independent of extracellular Na+, Ca2+ and T-type calcium channels, but requires inward rectifier K+ channels (Kirs). The present study demonstrates that Phe enhances GABAergic transmission onto mPFC pyramidal neurons through inhibiting interneurons Kirs, which further depolarizes interneurons leading to increase in Ca2+ influx via T-type calcium channels. Our results may provide a cellular and molecular mechanism that helps explain alpha(1)-AR-induced PFC dysfunction. (C) 2015 IBRO. Published by Elsevier Ltd. All rights reserved.