The Journal of Neurophysiology Vol. 84 No. 2 August 2000, pp. 744-751
Copyright ©2000 by the American Physiological Society

Synaptic Actions of Neuropeptide FF in the Rat Parabrachial Nucleus: Interactions With Opioid Receptors

 ¹Division of Basic Medical Sciences, Memorial University of Newfoundland, St. John's, Newfoundland A1B 3V6; and  ²Department of Medicine (Neurology) and Division of Neuroscience, University of Alberta, Edmonton, Alberta T6G 2B7, Canada

Chen, Xihua, Jeffrey A. Zidichouski, Kim H. Harris, and Jack H. Jhamandas. Synaptic Actions of Neuropeptide FF in the Rat Parabrachial Nucleus: Interactions With Opioid Receptors. J. Neurophysiol. 84: 744-751, 2000. The pontine parabrachial nucleus (PBN) receives both opioid and Neuropeptide FF (NPFF) projections from the lower brain stem and/or the spinal cord. Because of this anatomical convergence and previous evidence that NPFF displays both pro- and anti-opioid activities, this study examined the synaptic effects of NPFF in the PBN and the mechanisms underlying these effects using an in vitro brain slice preparation and the nystatin-perforated patch-clamp recording technique. Under voltage-clamp conditions, NPFF reversibly reduced the evoked excitatory postsynaptic currents (EPSCs) in a dose-dependent fashion. This effect was not accompanied by apparent changes in the holding current, the current-voltage relationship or -amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-induced inward currents in the PBN cells. When a paired-pulse protocol was used, NPFF increased the ratio of these synaptic currents. Analysis of miniature EPSCs showed that NPFF caused a rightward shift in the frequency-distribution curve, whereas the amplitude-distribution curve remained unchanged. Collectively, these experiments indicate that NPFF reduces the evoked EPSCs through a presynaptic mechanism of action. The synaptic effects induced by NPFF (5 µM) could not be blocked by the specific µ-opioid receptor antagonist, D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH₂ (1 µM), but application of -opioid receptor antagonist Tyr-Tic-Phe-Phe (5 µM) almost completely prevented effects of NPFF. Moreover, the -opioid receptor agonist, Deltorphin (1 µM), mimicked the effects as NPFF and also occluded NPFF's actions on synaptic currents. These results indicate that NPFF modulates excitatory synaptic transmission in the PBN through an interaction with presynaptic -opioid receptors. These observations provide a cellular basis for NPFF enhancement of the antinociceptive effects consequent to central activation of -opioid receptors.