Spinal antinociceptive effect of substance P on the responses induced by intrathecally injected NMDA in mice.
Substance P (SP) has previously been shown to be involved in the transmission of nociceptive information in the spinal dorsal horn. In this study we investigated whether a functional interaction exists between SP and excitatory amino acids in the spinal cord of mice. Behavioral responses were observed after intrathecal co-administration of SP and N-methyl-D-aspartate (NMDA). The high dose (12 pmol) of SP potentiated NMDA (0.25 nmol)-induced behavior consisted of caudally directed licking and biting, while the low dose (1 pmol) of SP significantly reduced this behavior. This inhibitory effect of low dose of SP was blocked by intrathecal co-administration of opioid receptor antagonist naloxone (4 nmol). These results suggest that SP is also involved in the antinociception which is dependent on opioid mechanisms at the spinal level.
Masuyama
T
T
Department of Anesthesiology and Critical Care Medicine, Faculty of Medicine, Kagoshima University, Japan.
Shimizu
T
T
Iwashita
T
T
Yoshimura
N
N
Fukuda
T
T
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004357:Drug Synergism; D007278:Injections, Spinal; D008297:Male; D051379:Mice; D016202:N-Methylaspartate / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009619:Nociceptors / Q000187:drug effects*; D013116:Spinal Cord / Q000187:drug effects*; D013373:Substance P / Q000494:pharmacology*
D004338:Drug Combinations; D009292:Narcotic Antagonists; D013373:Substance P; D009270:Naloxone; D016202:N-Methylaspartate