Sympathoadrenal preganglionic neurons in the adult rabbit send their dendrites into the contralateral hemicord

Sympathetic preganglionic neurons projecting to the adrenal medulla of the adult rabbit were retrogradely labelled with horseradish peroxidase. Preganglionic neurons were located in thoracic spinal cord segments T3-T12, peaking in number at T8, and only ipsilateral to the side of injections. However, retrogradely labelled dendritic processes of preganglionic neurons in the intercalated nucleus pars paraependimalys, the intercalated nucleus, and possibly even in the intermediolateral cell column, were observed in the contralateral hemicord. This suggests that the activity of sympathoadrenal preganglionic neurons could be modulated by both ipsilaterally and contralaterally descending pathways.