Intrathecal co-administration of substance P and NMDA augments nociceptive responses in the formalin test.
The effects of intrathecal administration of substance P and N-methyl-D-aspartate (NMDA) were studied in the formalin test in mice. Both substances were administered 5 min before injection of formalin into the hind paw. Co-administration of substance P and NMDA intensified the response in both the 1st (0-10 min) and the 2nd phase (20-30 min) of the formalin test, and increased the duration of the response. The increase in the response to formalin depended on the formalin concentration and was significant with 1% and 5% concentrations of formalin but not with a 0.05% concentration. No increase in the response was observed when NMDA or substance P was given alone. These findings indicate that concurrent activation of spinal NMDA and substance P receptors induces an enhancement of spinal transmission of nociception, and that this enhancement is dependent on the intensity or the quality of the peripheral stimulus.
D000818:Animals; D005557:Formaldehyde; D007278:Injections, Spinal; D008297:Male; D051379:Mice; D016202:N-Methylaspartate / Q000008:administration & dosage / Q000494:pharmacology*; D009619:Nociceptors / Q000187:drug effects*; D010146:Pain / Q000139:chemically induced; D010147:Pain Measurement / Q000187:drug effects*; D013373:Substance P / Q000008:administration & dosage / Q000494:pharmacology*
D005557:Formaldehyde; D013373:Substance P; D016202:N-Methylaspartate