Whole‐cell recordings of inwardly rectifying K+ currents activated by 5‐HT1A receptors on dorsal raphe neurones of the adult rat.

Abstract

SUMMARY1. An inwardly rectifying K+ current activated by serotonin (5-HT) was recorded from acutely isolated adult dorsal raphe (DR) neurones using the whole-cell recording mode of the patch clamp technique.

Serotonin reduces synaptic excitation in the superficial medial entorhinal cortex of the rat via a presynaptic mechanism

“…The effect is mediated by a pertussis toxin-sensitive G-protein and the opening of a Ca¥-independent K¤ channel (Clarke, De Vivo, Beck, Maayani & Goldfard, 1987;Colino & Halliwell, 1987;Kelly, Larkman, Penington, Rainnie, McAllister-Williams & Hodgkiss, 1991;Penington, Kelly & Fox, 1993). Our findings in the EC neurons are consistent with an intrinsic mechanism as described by others (Segal, 1980;Andrade & Nicoll, 1987;Colino & Halliwell, 1987;Andrade, 1991).…”

How Much Serotonin in the CNS is Too Much?

“…For instance, 5HT at the concentration of approximately 10 -9 M could competitively displace 50% of competitors at the 5HT 1A R site, implying that a sub-nM concentration is able to activate 5HT 1A Rs. In support of this, as demonstrated in vitro in dorsal raphe slices, the inward current indicative of 5HT 1A R activity can be elicited by 5HT at concentration less than 1 nM with the EC 50 at 30 nM (Penington et al, 1993), closely in line with results obtained by radioligand binding assays. By contrast, other subtypes such as 5HT 2A Rs are unlikely to be affected by 5HT at such a low concentration.…”

Differential Effects of the 5-Hydroxytryptamine (5-HT)1AReceptor Inverse Agonists Rec 27/0224 and Rec 27/0074 on Electrophysiological Responses to 5-HT1AReceptor Activation in Rat Dorsal Raphe Nucleus and Hippocampus in Vitro

“…5-HT 1A receptors are G protein-coupled receptors (GPCR) expressed throughout the central nervous system (Pompeiano et al, 1992). Stimulation of 5-HT 1A receptors activates Gi/o proteins, leading to at least two different cellular responses: inhibition of adenylate cyclase and opening of inwardly rectifying K ϩ channels (Andrade and Nicoll, 1987;Fargin et al, 1989, Penington et al, 1993. 5-HT 1A receptors mediate the hyperpolarization of neurons in almost all the brain regions (see Barnes and Sharp, 1999), thereby exerting an inhibitory action on cell discharge, including the rhythmic firing of serotonergic cells in the raphe nuclei.…”