Lack of a bilateral projection of individual spinal neurons to the lateral reticular nucleus in the rat: a retrograde, non-fluorescent, double labeling study.

The projection of spinal neurons to the lateral reticular nucleus of the rat was investigated with a non-fluorescent double retrograde tracing technique. Either a gold-lectin tracer or cholera toxin-b-subunit was injected into the lateral reticular nucleus on each side of the brain. Retrogradely labeled neurons were encountered bilaterally throughout the spinal cord. Double labeled neurons, however, were seldom seen (< 2% of the total number of labeled neurons) and those that were of passing fibers. It is concluded that most spinoreticular neurons project to either the ipsi- or contralateral lateral reticular nucleus, suggesting that each side receives a unique spinal input.