The role of the ORL1 receptor in the modulation of spinal neurotransmission by nociceptin/orphanin FQ and nocistatin

Nociceptin/orphanin FQ and nocistatin are two neuropeptides with opposing effects on spinal neurotransmission and nociception. Nociceptin/orphanin FQ selectively suppresses excitatory glutamatergic neurotransmission, while nocistatin selectively interferes with glycinergic and gamma -aminobutyric acid (GABA)-ergic transmission. Here, we performed whole-cell patch-clamp recordings from superficial rat spinal cord dorsal horn neurons to investigate the role of the opioid receptor-like (ORL)1 receptor for modulatory actions of these peptides. The partial ORL1 receptor antagonist [phe(1)Psi (CH2-NH)Gly(2)]nociceptin-competitively reversed the effects of nociceptin/orphanin FQ on excitatory neurotransmission (estimated pA(2) 6.43), but left the suppression of inhibitory synaptic transmission by nocistatin unaffected. These results indicate that the inhibitory action of nociceptin/orphanin FQ on glutamatergic transmission is mediated via ORL1 receptors, while nocistatin acts via a different so far unidentified receptor. (C) 2001 Published by Elsevier Science B.V.