Nociceptin/Orphanin FQ Modulation of Ionic Conductances in Rat Basal Forebrain Neurons

Abstract

Nociceptin/orphanin FQ (N/OFQ) is an endogenous opioid-like heptadecapeptide that plays an important role in a variety of physiological functions. N/OFQ and its receptor opioid receptor-like orphan receptor-1 are abundant in the diagonal band of Broca (DBB), a basal forebrain nucleus where the loss of cholinergic neurons is linked to memory and spatial learning deficits. In the whole animal, central injections of N/OFQ have been shown to disrupt spatial learning. In this study, we investigated the basis for these behavioral observations by examining the cellular effects of N/OFQ on chemically identified DBB neurons. Whole cell patch-clamp recordings were performed on enzymatically dissociated DBB neurons. Under voltage-clamp conditions, bath application of N/OFQ (10 pM-1 M) resulted in a dose-dependent depression of whole cell currents. Single cell reverse transcription-polymerase chain reaction analysis identified cholinergic and fewer GABAergic cells to be N/OFQresponsive.[Nphe 1 ]nociceptin-(1-13)-NH 2 and CompB (J-113397) antagonized the N/OFQ response, but both compounds also displayed partial agonist activity. Using a combination of channel blockers we determined that the effects of N/OFQ were mediated via a suite of Ca 2ϩ (N-and L-type) and Ca 2ϩ -dependent K ϩ (iberiotoxin-sensitive) conductances. In addition, biophysical analysis of voltage subtraction protocols revealed that N/OFQ reduces transient outward and the delayed rectifier K ϩ currents. Because N-type and L-type Ca 2ϩ channels are important in the context of neurotransmitter release, our observations indicate that N/OFQ inhibition of Ca 2ϩ -dependent conductances in cholinergic neurons would be expected to result in depression of acetylcholine release, which may explain the behavioral actions of N/OFQ in the brain.

The NOP (ORL1) receptor antagonist Compound B stimulates mesolimbic dopamine release and is rewarding in mice by a non‐NOP‐receptor‐mediated mechanism

“… Bigoni et al ., 2000 ; Ozaki et al ., 2000a ; 2000b ; Ichikawa et al ., 2001 ) or those employing CompB for verifying that actions of N/OFQ are mediated through the NOP receptor (e.g. Chin et al ., 2002 ; Mela et al ., 2004 ). In vivo studies employing CompB are fewer, although an appreciable number have recently accumulated.…”

β-Amyloid enhances intracellular calcium rises mediated by repeated activation of intracellular calcium stores and nicotinic receptors in acutely dissociated rat basal forebrain neurons

“…The protocol for preparation of tissue was reviewed and approved by the University of Alberta Health Sciences Laboratory Animal Services (Protocol number 154/04/05). Details of the procedure for acute dissociation of neurons from the DBB have been previously described (Chin et al, 2002). Briefly, brains were quickly removed from decapitated male Sprague Dawley rats (21-25 days postnatal) and placed in cold artificial cerebrospinal fluid (ACSF) that contained (in mM) 140 NaCl, 2.5 KCl, 1.4 CaCl 2 , 5 MgCl 2 , 10 HEPES, and 33 Dglucose (pH 7.4).…”

“…Dissociated cells were then plated on poly-L-lysine (0.005% w/ v)-coated cover slips and viewed under an inverted microscope (Zeiss Axiovert 35). Neurons were identified based upon previously established visual criteria (Chin et al, 2002). Basal forebrain neurons could be differentiated from glia based upon the presence of truncated dendrites at the conspicuously larger neurons.…”

GIRK channel-mediated inhibition of melanin-concentrating hormone neurons by nociceptin/orphanin FQ

“…In addition, N/OFQ was found to inhibit voltage-gated calcium currents. Although we cannot rule out an effect on other ionic currents known to be modulated by N/OFQ such as BK and delayed rectifier currents (Chin et al 2002;Qu et al 2007), we conclude that the majority of the observed inhibition of MCH neurons results from modulation of GIRK and calcium channel activity.…”