Involvement of CGRP and CGRP1 receptor in nociception in the nucleus accumbens of rats

The present study was performed to investigate: the role of calcitonin gene -related peptide (CGRP) and its antagonist CORP8-37 on nociception in the n ucleus accumbens of rats. Hindpaw withdrawal latencies (HWLs) to noxious st imulation induced by hot plate and Randall Selitto tests were measured. The HWL to both thermal and mechanical stimulation increased significantly aft er intra-nucleus accumbens administration of 0.5 or 1 nmol of CGRP, but nor 0.1 nmol, indicating that CGRP plays an anti-nociceptive effect in the nuc leus accumbens of rats. The anti-nociceptive effect induced by intra-nucleu s accumbens administration of 1 nmol of CGRP was blocked significantly by f ollowing intra-nucleus accumbens administration of 1 nmol of CGRP8-37, a se lective antagonist of CGRP1 receptor. Furthermore, the HWLs to both thermal and mechanical stimulation decreased significantly after intra-nucleus acc umbens administration of 0.02, 0.1 and 0.5 nmol of CGRP8-37 alone. The hype ralgesic effect of intra-nucleus accumbens administration of CGRP8-37 laste d for more than 60 min after the injection, suggesting that CGRP1 receptor is involved in anti-nociception in the nucleus accumbens of rats. The resul ts indicate that CGRP and CGRP1 receptor have important roles in nociceptiv e modulation in the nucleus accumbens of rats. (C) 2001 Elsevier Science B. V. All rights reserved.