Substance P and calcitonin gene-related peptide synergistically modulate the gain of the nociceptive flexor withdrawal reflex in the rat.
A comparison has been made between the effects of intrathecally administered L-glutamate, L-aspartate, substance P and calcitonin gene-related peptide (CGRP) on the excitability of rat flexor alpha-motoneurons activated monosynaptically by Ia afferents and polysynaptically by high mechano-threshold cutaneous afferents. At doses that do not modify the monosynaptic reflex, substance P, CGRP and some factor released from sural C-fibres increase the excitability of the nociceptive flexion reflex for prolonged periods in a multiplicative fashion. The excitatory amino acids have no such action. We suggest that one role for C-afferent neuropeptides is a long-acting gain modulation of nociceptive inputs into the spinal cord.
D000818:Animals; D001224:Aspartic Acid / Q000494:pharmacology; D015740:Calcitonin Gene-Related Peptide; D004357:Drug Synergism; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D007278:Injections, Spinal; D007866:Leg; D009046:Motor Neurons / Q000187:drug effects; D009132:Muscles / Q000294:innervation / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000494:pharmacology*; D009619:Nociceptors / Q000502:physiology*; D010812:Physical Stimulation; D051381:Rats; D012018:Reflex / Q000502:physiology*; D013373:Substance P / Q000494:pharmacology*; D014034:Toes
D005971:Glutamates; D009419:Nerve Tissue Proteins; D001224:Aspartic Acid; D013373:Substance P; D018698:Glutamic Acid; D015740:Calcitonin Gene-Related Peptide