title: Sensory neuropeptide interactions in the production of plasma extravasation in the rat.
abstract: We used an experimental model of neurogenic inflammation to study the contribution of the primary afferent peptides substance P, calcitonin gene-related peptide, galanin and somatostatin to plasma extravasation in rat synovium. Perfusion of the C-fiber excitotoxin, capsaicin (1.6 mM), through the knee joint of the pentobarbital anesthetized rat, increased plasma extravasation transiently (< 30 min). Perfusion of substance P (1 microM) or calcitonin gene-related peptide (100 nM), two primary afferent neuropeptides that are released by acute capsaicin administration, had no significant effect on plasma extravasation. Co-perfusion of these two neuropeptides, however, evoked an increase in plasma extravasation that was greater than that produced by capsaicin remaining above 250% of the baseline level by the end of the perfusion period (55 min). Capsaicin co-perfused with either galanin (100 nM) or somatostatin (1 microM) failed to increase plasma extravasation. Neither galanin nor somatostatin significantly affected increase in plasma extravasation induced by co-perfusion of substance P plus calcitonin gene-related peptide. Therefore, we suggest that galanin and somatostatin inhibit, presynaptically, the release of substance P and calcitonin gene-related peptide from primary afferent terminals. The interactions among these four neuropeptides provide a novel mechanism for the regulation of primary afferent neurogenic inflammation.
mesh_terms: D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000502:physiology; D002211:Capsaicin / Q000494:pharmacology; D019004:Galanin; D008297:Male; D009475:Neurons, Afferent / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism*; D010455:Peptides / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013004:Somatostatin / Q000502:physiology; D013373:Substance P / Q000502:physiology
chemical_list: D009479:Neuropeptides; D010455:Peptides; D013373:Substance P; D013004:Somatostatin; D019004:Galanin; D015740:Calcitonin Gene-Related Peptide; D002211:Capsaicin