Modulation of cat monosynaptic reflexes by substance P.
Substance P (SP) applied by iontophoresis at different current strengths to single motoneurons of cat spinal cord did not cause these units to discharge. SP produced a gradual and prolonged change in synaptic excitability as measured by response to dorsal root stimulation. The effect outlasted application of SP. The lowest effective dose of SP diminished motoneuron response to dorsal root stimulation (inhibitory modulation). Doses 2-4 times as great enhanced the response to dorsal root stimulation (facilitatory modulation) without causing the motoneuron to discharge spontaneously. These observations suggest that one physiological role of SP is modulation of synaptic transmission, i.e. alteration of efficacy of transmission without acting as a primary transmitter at the postsynaptic membrane.
D000818:Animals; D002415:Cats; D005071:Evoked Potentials / Q000187:drug effects; D009046:Motor Neurons / Q000187:drug effects; D009433:Neural Inhibition / Q000187:drug effects; D012023:Reflex, Monosynaptic / Q000187:drug effects*; D013116:Spinal Cord / Q000187:drug effects; D013373:Substance P / Q000494:pharmacology*; D009435:Synaptic Transmission / Q000187:drug effects
D013373:Substance P