Splanchnic afferent input to the lateral reticular nucleus of the cat.

The afferent input from splanchnic nerves to the lateral reticular nucleus (LRN) was studied in anesthetized cats. The activity of neurons of the parvi- and magnocellular regions of the nucleus was recorded by means of extracellular microelectrodes. The LRN neurons were stereotaxically located and identified by their response to antidromic stimulation of the cerebellar cortex. Activity of the LRN neurons studied was modified by electrical stimulation of the ipsi- and contralateral splanchnic nerves, and by mechanical stimulation of peritoneal receptors. Response latencies to stimulation of the splanchnic nerves were measured, and conduction velocities of peripheral fibers were determined; most of them were myelinated fibers with a small diameter (sub-groups of A- A gamma delta) and were connected with 'peritoneal movement mechanoreceptors'. Numerous convergences were observed. All of the tested neurons which responded to stimulation of the homolateral splanchnic nerve also responded to stimulation of the contralateral splanchnic and to diverse somatic stimulations. In 90% of the neurons tested, a splanchno-cortical convergence (sensory-somatic cortex) was observed. Two possible roles of splanchnic afferents that activate neurons of the LRN were considered: (1) they might, like other spinal inputs, influence LRN and cerebellar control of motor activity; and (2) they might also participate in cardiovascular regulations in which the LRN is involved.