The inhibitory effect of substance P antagonist, CP-96,345, on the late discharges of nociceptive neurons in the rat superficial spinal dorsal horn.
The effects of local spinal applications of the substance P antagonist, CP-96,345, on the electrically-evoked discharges of nociceptive neurons were examined in the superficial spinal dorsal horn of adult rats anesthetized with sodium pentobarbital. Extracellular single-unit recordings were made from lumbar spinal dorsal horn neurons which were excited by noxious mechanical stimulation and had early and late discharges evoked by A- and C-fiber inputs, respectively, following transcutaneous electrical stimulation. CP-96,345 was applied directly onto the surface of the spinal cord close to the recording sites. A dose of 50 nmol of CP-96,345 drastically inhibited the late discharges of 80% of neurons, without affecting early discharges significantly. This study demonstrated the specific inhibitory effect of CP-96,345 on the late discharges of a restricted population of spinal dorsal horn neurons. These results illustrate the important role of substance P in nociceptive transmission mediated by primary afferent C-fibers in normal acute pain.
Toda
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T
Department of Physiology, School of Dentistry, Tohoku University, Sendai, Japan.
Hayashi
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H
D000818:Animals; D001713:Biphenyl Compounds / Q000494:pharmacology*; D004558:Electric Stimulation; D004594:Electrophysiology; D005260:Female; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D009412:Nerve Fibers / Q000187:drug effects; D009413:Nerve Fibers, Myelinated / Q000187:drug effects; D009474:Neurons / Q000187:drug effects*; D009619:Nociceptors / Q000187:drug effects*; D010812:Physical Stimulation; D051381:Rats; D017208:Rats, Wistar; D013116:Spinal Cord / Q000166:cytology* / Q000187:drug effects; D013373:Substance P / Q000037:antagonists & inhibitors*
D001713:Biphenyl Compounds; D006993:Hypnotics and Sedatives; D013373:Substance P; C066892:CP 96345