title: A biphasic excitability change in hindlimb motoneurons evoked by stimulation of the nucleus raphes magnus in the cat.
abstract: 1. The influence of electrical stimulation of the nucleus raphes magnus (RM) on spinal segmental systems were examined. 2. RM stimulation produced an initial increase and a subsequent suppression of the amplitude of both fiextor and extensor lumbar monosynaptic reflex potentials (MSRs). 3. Intracellular recordings were made from alpha-motoneurons of the common peroneal nerve (flexor) and the tibial nerve (extensor). RM stimulation evoked postsynaptic potentials with a time course similar to that of MSR facilitation. 4. RM stimulation inhibited the aggregate excitatory synaptic potential (EPSP) evoked by stimulation of group I afferent fibers without apparent changes in the motoneuronal membrane potential. 5. These data suggest that the RM-evoked biphasic effect on MSR consists of early facilitation due to EPSP, and late inhibition possibly due to presynaptic inhibition of group I afferent fibers.
authors.affiliation: Department of Physiology, Sapporo Medical College, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Edamura
authors.forename: M
authors.initials: M
authors.lastname: Aoki
mesh_terms: D000818:Animals; D002415:Cats; D004558:Electric Stimulation; D006614:Hindlimb / Q000294:innervation*; D008564:Membrane Potentials; D009046:Motor Neurons / Q000502:physiology*; D009433:Neural Inhibition; D011903:Raphe Nuclei / Q000502:physiology*; D012018:Reflex / Q000502:physiology; D013116:Spinal Cord / Q000502:physiology