Activation of pontine and bulbar reticulo-spinal neurons in the cat by somatosensory stimuli of different modalities

Abstract

The response pattern of reticulo-spinal (RS) neurons in two reticulo-spinal structures (n. reticularus pontis caudalis and n. reticularis gigantocellularis) to both electrical (somatic) nerve stimulation and natural mechanical innocuous (tapping with varying force) and noxious (pinch and prick) stimulation were investigated in chloralose-anesthetized cats. Bulbar and pontine neurons were found to vary considerably in their sensory characteristics: of the former 43% were activated only by high-threshold electrical nerve stimulation and noxious stimuli, while the remainder responded to innocuous stimuli as well. In the case of pontine neurons 81% produced a response to stimulation of low-threshold nerve fibers, and to innocuous as well as noxious stimuli. A relationship was found between the sensory characteristics of reticulo-spinal neurons and their axon conductance velocities. Various aspects and the likely functional significance of specialization in brainstem neurons of the pontine and bulbar reticular formation come under discussion.