• Yi Yan and Long-Chuan Yu.
• Laboratory of Neurobiology, College of Life Sciences, and National Laboratory of Biomembrane and Membrane Biotechnology, Peking University, Beijing, Peoples Republic of China.
• J. Neurosci. Res. 2004 Jul 1; 77 (1): 148-52.

AbstractThe present study was performed to explore the involvement of opioid receptors in the calcitonin gene-related peptide 8-37 (CGRP8-37, an antagonist of CGRP receptor)-induced inhibition of the activity of wide-dynamic-range (WDR) neurons in the spinal dorsal horn of rats. Extracellular recording was performed with a multibarrelled glass micropipette, and the chemicals were delivered by micro-iontophoresis. The discharge frequency of WDR neurons was evoked by subcutaneous electrical stimulation applied to the ipsilateral hindpaw. Iontophoretic application of CGRP8-37 by an ejection current of 160 nA induced significant inhibition of the discharge frequency of WDR neurons. The inhibitory effect of CGRP8-37 on the activity of WDR neurons was attenuated by later iontophoretic application of the opioid antagonist naloxone. Furthermore, the effect of CGRP8-37 was attenuated by either iontophoretic application of the kappa-receptor antagonist nor-binaltorphimine (nor-BNI) or the mu-receptor antagonist beta-funaltrexamine (beta-FNA) but not by the delta-receptor antagonist naltrindole. The results indicate that kappa- and mu-opioid receptors on the membrane of WDR neurons are involved in the modulation of CGRP8-37-induced antinociception in dorsal horn of the spinal cord in rats.Copyright 2004 Wiley-Liss, Inc.

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