Substance P and somatostatin modulate spinal cord excitability via physiologically different sensory pathways.
The effect of intrathecally injected substance P and somatostatin on spinal flexion reflex excitability was examined in decerebrate, spinalized, unanaesthetized rats. Substance P increased the excitability of the spinal cord to mechanical and thermal stimuli suprathreshold for C-afferents. Somatostatin had a similar effect with thermal, but not with mechanical stimuli. It is suggested that both peptides are released in association with C-afferent activation. Substance P may be released by polymodal nociceptors whereas somatostatin may be released by thermosensitive C-afferents.
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Wiesenfeld-Hallin
D000200:Action Potentials; D000344:Afferent Pathways / Q000187:drug effects / Q000502:physiology; D000818:Animals; D004558:Electric Stimulation; D006358:Hot Temperature; D009475:Neurons, Afferent / Q000187:drug effects* / Q000502:physiology; D010146:Pain / Q000503:physiopathology; D051381:Rats; D012018:Reflex / Q000187:drug effects / Q000502:physiology; D013004:Somatostatin / Q000494:pharmacology*; D013116:Spinal Cord / Q000187:drug effects* / Q000502:physiology; D013373:Substance P / Q000494:pharmacology*
D013373:Substance P; D013004:Somatostatin