Suppression of dental pulp-evoked trigeminal responses by nucleus reticularis gigantocellularis in the cat.

The temporal effect of electrical stimulation of the nucleus reticularis giganto-cellularis (NRGC) on the dental pulp-evoked field potential in the subnucleus oralis of the spinal trigeminal complex (oralis potential) and on the jaw-opening reflex was investigated in precollicular decrebrate cats using the conditioning-testing technique. NRGC activation invariably elicited suppression of the oralis potential, the degree and duration of which were related to the reticular stimulus parameters. When activated at optimal stimulus parameters, NRGC was found to exert parallel inhibition of oralis potential and jaw-opening reflex lasting 500 to 800 ms in many instances. The possibility that NRGC may interrupt the transmission of noxious signals from the dental pulp by promoting a depolarization of pulpal afferents is discussed in light of the current concepts on opiate receptors and their ligands and parallel studies in this laboratory.