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Involvement of PACAP receptor in primary afferent fibre‐evoked responses of ventral roots in the neonatal rat spinal cord
Author(s) -
Sakashita Yoshihiko,
Kurihara Takashi,
Uchida Daigaku,
Tatsuno Ichiro,
Yamamoto Tatsuo
Publication year - 2001
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0703980
Subject(s) - spinal cord , depolarization , vasoactive intestinal peptide , saphenous nerve , nociception , receptor , agonist , medicine , nociceptor , receptor antagonist , dorsal root ganglion , endocrinology , chemistry , anatomy , neuroscience , antagonist , biology , neuropeptide
The role of PACAP receptor in nociceptive transmission was investigated in vitro using maxadilan, a PACAP receptor selective agonist and max.d.4, a PACAP receptor selective antagonist. Potentials, from a ventral root (L3 – L5) of an isolated spinal cord preparation or a spinal cord – saphenous nerve – skin preparation from 0 – 3‐day‐old rats, were recorded extracellularly. In the isolated spinal cord preparation, single shock stimulation of a dorsal root at C‐fibre strength induced a slow depolarizing response lasting about 30 s (slow ventral root potential; slow VRP) in the ipsilateral ventral root of the same segment. Bath‐application of max.d.4 (0.01 – 3 μ M ) inhibited the slow VRP in a concentration‐dependent manner. In the spinal cord – saphenous nerve – skin preparation, application of capsaicin (0.1 μ M ) to the skin evoked a depolarization of the ventral root. This response was also depressed by max.d.4 (1 μ M ). Application of maxadilan evoked a long‐lasting depolarization in a concentration‐dependent manner in the spinal cord preparation. In the presence of max.d.4 (0.3 μ M ), the concentration response curve of maxadilan was shifted to the right. Reverse transcription‐polymerase chain reaction (RT – PCR) experiments demonstrated the existence of PACAP receptor and VPAC 2 receptor in the neonatal rat spinal cord and [ 125 I]‐PACAP27 binding was displaced almost completely by maxadilan and max.d.4, but not by vasoactive intestinal peptide (VIP). These data indicate that PACAP receptor is dominantly distributed in the neonatal rat spinal cord. The present study suggests that PACAP receptor may play an excitatory role in nociceptive transmission in the neonatal rat spinal cord.British Journal of Pharmacology (2001) 132 , 1769–1776; doi: 10.1038/sj.bjp.0703980