Somatosensory Systems, PainEffects of intrathecal nocistatin on the flexor reflex and its interaction with orphanin FQ nociceptinXu, Isabella S.1; Hashemi, Maryam1; Caló, Girolamo2; Regoli, Domenico2; Wiesenfeld-Hallin, Zsuzsanna1; Xu, Xiao-Jun1,3 Author Information 1Department of Medical Laboratory Sciences and Technology, Division of Clinical Neurophysiology, Karolinska Institute, Huddinge University Hospital, S-141 86 Huddinge, Sweden 2Department of Experimental and Clinical Medicine, Section of Pharmacology, University of Ferrara, Ferrara, Italy 3Corresponding Author: Xiao-Jun Xu ACKNOWLEDGEMENTS: The present study was supported by Swedish Medical Research Council (07913 to Z.W.-H. and 12168 to X.-J.X.), Astra Pain Control AB, research funds of the Karolinska Institute and resources of the Center for Clinical Research at Huddinge University Hospital. Received 15 September 1999; accepted 24 September 1999 NeuroReport: November 26, 1999 - Volume 10 - Issue 17 - p 3681-3684 Buy Abstract We studied the effects of intrathecal (i.t.) nocistatin, a peptide identified from the precursor of orphanin FQ/nociceptin (OFQ) on the spinal nociceptive flexor reflex in decerebrate, spinalized, unanesthetized rats and its interaction with i.t. OFQ. Nocistatin induced a moderate, non-dose-dependent facilitation of the flexor reflex without producing reflex depression whereas i.t. OFQ induced a biphasic dose-dependent facilitatory and inhibitory effect. The facilitatory effect of low dose (0.55 pmol) OFQ was significantly increased by nocistatin. On the other hand, the duration, but not magnitude, of reflex depression induced by a high (550 pmol) dose of OFQ was significantly shortened by 5.5 nmol nocistatin. Thus, nocistatin interacts with OFQ in a complex fashion, increasing excitation and reducing inhibition. No evidence was obtained for an antinociceptive effect of nocistatin in rat spinal cord. © 1999 Lippincott Williams & Wilkins, Inc.