In vivo release of substance P in cat dorsal horn studied with microdialysis.
Variations in the extracellular concentration of substance P (SP) were measured in cat dorsal horn in vivo by microdialysis and radioimmunoassay. Electrical unilateral stimulation of the sciatic nerve was used to evoke release of SP. At high-intensity stimulation, activating slowly conducting (approx. 0.9 m/s) fibres, there was an increase in substance P-like immunoreactivity (SP-LI) to 338% of the preceding control value (P less than 0.05, n = 5) in the dialysates collected at levels L6-L7 at the stimulated side. A less pronounced increase, to 164% of the basal level, was found at the contralateral side. More cranially (L1-L5) in the dorsal horn at the stimulated side, only a moderate or no increase in SP-LI was seen. Stimulation with low intensity, sufficient to activate fast (greater than 20 m/s), but not slowly conducting fibres, evoked no increase in SP-LI. The results indicate that unilateral peripheral C-fibre activation induces a local SP release in the dorsal horn present also on the side not stimulated.
D000200:Action Potentials; D000818:Animals; D002415:Cats; D003956:Dialysis; D004558:Electric Stimulation; D005260:Female; D008297:Male; D009412:Nerve Fibers / Q000502:physiology; D010525:Peripheral Nerves / Q000378:metabolism / Q000502:physiology*; D011863:Radioimmunoassay; D012584:Sciatic Nerve / Q000502:physiology; D013116:Spinal Cord / Q000378:metabolism*; D013373:Substance P / Q000378:metabolism*
D013373:Substance P