Projection to the lateral reticular nucleus from neurons located in C6-C7 segments of the spinal cord. An electrophysiological study in the cat.

Spinoreticular neurons projecting to the lateral reticular nucleus (LRN) were investigated electrophysiologically in the cervical enlargement of the cat spinal cord. Experiments were performed on alpha-chloralose anaesthetized animals. Antidromic action potentials were recorded extracellularly from cells located in C6 and C7 segments following stimulation of the ipsilateral LRN. The total sample included 50 neurons. Their cell bodies were found to be distributed in Rexed's laminae VI-VIII of the gray matter. Axonal conduction velocities ranged from 14.7 to 89.7 ms-1. Considerable differences between particular cases enabled two separate groups of slower and faster conduction to be distinguished. Values for these two groups were 14.7-44.3 ms-1 and 52.2-89.7 ms-1, respectively. Discrete differences with regard to the location of these groups were also pointed out. Such differentiation suggests that a proportion of axons from the slower conducting pool may be in fact collaterals of neurons that project to other brainstem centers or to lower levels of the spinal cord.