An ionophoretic study of the responses of rat caudal trigeminal nucleus neurones to non‐noxious mechanical sensory stimuli.

Publisher Website
Google Scholar
Abstract
Extracellular recordings of the repsonses of single caudal trigeminal nucleus neurons to non-noxious and noxious facial stimuli and to ionophoretically applied L-glutamate, L-aspartate and acetylcholine [ACh] were made in urethane anesthetized rats. Neurons excited by non-noxious mechanical stimuli were located primarily in the magnocellular part of nucleus caudalis; neurons excited by both noxious and non-noxious stimuli were located either ventromedially to the magnocellular part of nucleus caudalis or superficially to the substantia gelatinosa. Both L-aspartate and L-glutamate excited all neurons tested in nucleus caudalis, while ACh excited only 31% of the neurons tested. Responses of nucleus caudalis neurons to non-noxious sensory stimulation were not antagonized by the excitatory amino acid antagonist D-.alpha.-aminoadipate, but were antagonized by cis-2,3-piperidine dicarboxylate and .gamma.-D-glutamylglycine, 2 excitatory amino acid antagonists with a broader spectrum of action. The chemical synaptic transmitter of non-nociceptive mechanoreceptive primary afferent fibers to nucleus caudalis may be a ligand for an excitatory amino acid receptor other than a D-.alpha.-aminoadipate-sensitive receptor. The synaptic receptor may thus be of the kainate or quisqualate type, and the transmitter possibly L-glutamate, L-aspartate or an as yet unidentified substance.