Efferent projections from the subnucleus reticularis dorsalis (SRD): a Phaseolus vulgaris leucoagglutinin study in the rat.

Small iontophoretic applications of Phaseolus vulgaris leucoagglutinin (PHA-L) were used in rats to study the efferent projections from a restricted region in the reticular formation of the caudal medulla: the subnucleus reticularis dorsalis (SRD). It was found that fibres from SRD project mainly to the spinal cord, the oral motor nuclei, the dorsal accessory inferior olive, the giganto- and parvo-cellular nuclei of the reticular formation and the parafascicular and ventromedian nuclei of the thalamus. Together with our previous electrophysiological findings, this study suggests that the SRD could be involved both in the control of pain processing and in motor reactions elicited by noxious events.