Negative potentials evoked by nucleus reticularis gigantocellularis in the spinal trigeminal tract of the cat

Abstract

In cats that were precollicularly decerebrated, bilateral elactrical stimulation of the nucleus reticularis gigantocellularis (NRGC) evoked negative potentials in the spinal trigeminal tract at the level of the subnucleus oralis of the spinal trigeminal nuclear complex. These negative potentials exhibited two types of configurations that differed in the slope of the rising and declining phase, duration, and amplitude of the negative wave. They were also found to develop as a function of the reticular stimulus parameters. Thus, they possessed electrophysiologic characteristics similar to the dorsal root potentials induced by comparable reticular activation in the spinal cord. The time course of the NRGC-evoked negative potential paralleled the inhibition of dental pulp-elicited responses in the subnucleus oralis, promoted by the same reticular stimulation. As the dorsal root potential is generally taken to be a manifestation of primary afferent depolarization, it is suggested, by extrapolation, that the NRGC may, at least in part, suppress the transmission of nociceptive signals from the dental pulp by a depolarization of the pulpal afferent fibers.