Modality Specific Analgesia Produced by Intrathecal Anti-Substance P Antibody

Abstract

Substance P (SP) is a putative primary afferent transmitter of nociceptive information [1]. Intrathecal injection of SP produces an increased sensitivity to heat [2,3] and pressure [4] in tests for nociceptive thresholds. Recently, SP was shown to be released from spinal cord by noxious pressure but not noxious thermal stimulation, while somatostatin (SST) was selectively released by noxious thermal stimulation [5] suggesting a modality specific role for these peptides in relation to pain. Previously, antibodies to SP (anti-SP) and SST (anti-SST) have been used to demonstrate the presence of SP and SST immunoreactive fibers in the dorsal horn of the spinal cord [6]. In this study we have used antibodies to SP and SST to determine whether a modality specific analgesia for these peptides could be demonstrated. The present experiments first tested the tail flick latency to heat and the paw withdrawal response to pressure in rats following intrathecal injections of anti SP, anti-SST or normal serum. In a second experiment, the behavioral effects of anti-SP serum were compared to normal serum in rats which were tested prior to injection.