Formalin-induced nociceptive responses in diabetic mice.
In non-diabetic mice, s.c. injection of formalin to the hindpaw had a biphasic effect: an immediate nociceptive response (first-phase) followed by a tonic response (second-phase). However, only the immediate nociceptive response was observed in diabetic mice. The duration of the first-phase response was significantly longer in diabetic mice than in non-diabetic mice. In diabetic mice, when spantide, an antagonist of substance P, reduced the duration of the nociceptive response in the first-phase to the levels that were observed in non-diabetic mice, the second-phase response appeared. The second phase also became apparent in diabetic mice after pretreatment with naltrindole (3 mg/kg), an antagonist of delta-opioid receptors. These results suggest that a negative control system, which is mediated by delta-opioid receptors and links substance P with somatostatin-mediated nociceptive transmission, may inhibit the formalin-induced second-phase of the nociceptive response in diabetic mice.
Kamei
J
J
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Hoshi University, Tokyo, Japan.
Hitosugi
H
H
Kasuya
Y
Y
D000700:Analgesics / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005557:Formaldehyde / Q000494:pharmacology*; D007278:Injections, Spinal; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009271:Naltrexone / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D009619:Nociceptors / Q000187:drug effects*; D017465:Receptors, Opioid, delta / Q000187:drug effects; D013373:Substance P / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology
D000700:Analgesics; D009292:Narcotic Antagonists; D017465:Receptors, Opioid, delta; D005557:Formaldehyde; D013373:Substance P; D009271:Naltrexone; C042867:spantide; C055382:naltrindole