LACK OF A BILATERAL PROJECTION OF INDIVIDUAL SPINAL NEURONS TO THE LATERAL RETICULAR NUCLEUS IN THE RAT - A RETROGRADE, NONFLUORESCENT, DOUBLE-LABELING STUDY

The projection of spinal neurons to the lateral reticular nucleus of t he rat was investigated with a non-fluorescent double retrograde traci ng technique. Either a gold-lectin tracer or cholera toxin-b-subunit w as injected into the lateral reticular nucleus on each side of the bra in. Retrogradely labeled neurons were encountered bilaterally througho ut the spinal cord. Double labeled neurons, however, were seldom seen (<2% of the total number of labeled neurons) and those that were could , at least partly, be ascribed to inadvertent labeling of passing fibe rs. 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.