Integration in trigeminal premotor interneurones in the cat. 2. Functional characteristics of neurones in the subnucleus-gamma of the oral nucleus of the spinal trigeminal tract with a projection to the digastric motoneurone subnucleus.
Seventy-one (n = 71) premotor interneurones have been localized by extracellular recordings within the subnucleus-gamma of the oral nucleus of the spinal trigeminal tract (NVspo-gamma) in nineteen chloralose anaesthetized cats. The neurons were antidromically activated by microstimulation (minimum = 3 microA) applied to the digastric motoneurone subnucleus of the trigeminal motor nucleus. Fifty-one (n = 51) of the interneurones were discharged from the ipsi- and nineteen (n = 19) from the contralateral digastric subnucleus. One neurone out of four tested was antidromically activated from both stimulation sites suggesting a bifurcated axon. The identified premotor neurones had a unique convergence profile of oral and perioral primary afferents. Latency calculations indicated that at least 55% of these interneurones were monosynaptically activated by low stimulus strength applied to the inferior alveolar (minimum = 1.0 T) and/or the lingual nerve (minimum = 1.0 T). The thresholds for evoking the neuronal discharges coincided statistically with those required to evoke a jaw opening reflex response by stimulation of the same nerves. It is suggested that the specific group of NVspo-gamma interneurones under different contexts mediates the disynaptic reflex and participates in the centrally and reflexly evoked "patterning" adjustments of the digastric jaw opening motoneurones during ongoing jaw movements. A companion paper reports the convergence of descending cortical, tectal and ascending cervical inputs, as well as of oro-facial and neck primary afferent inputs onto an unselected population of interneurones in the NVspo-gamma (Westberg and Olsson 1991).
Olsson
K A
KA
Department of Physiology, University of Umeå, Sweden.
Westberg
K G
KG
D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001933:Brain Stem / Q000502:physiology; D002415:Cats; D004558:Electric Stimulation / Q000379:methods; D005071:Evoked Potentials; D005260:Female; D007839:Functional Laterality; D007395:Interneurons / Q000502:physiology*; D008297:Male; D009046:Motor Neurons / Q000502:physiology; D009334:Neck Muscles / Q000294:innervation*; D009431:Neural Conduction; D012018:Reflex; D014276:Trigeminal Nerve / Q000502:physiology*; D014278:Trigeminal Nuclei / Q000502:physiology; D014279:Trigeminal Nucleus, Spinal / Q000033:anatomy & histology / Q000502:physiology*