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

• Published in: Experimental brain research 1991, Vol.84 (1), p.115-124
• Main Authors: Olsson, K A, Westberg, K G
• Format: Article
• Language: English
• Subjects: Afferent Pathways - physiology; Animals; Brain Stem - physiology; Cats; Electric Stimulation - methods; Evoked Potentials; Female; Functional Laterality; Interneurons - physiology; Male; Motor Neurons - physiology; Neck Muscles - innervation; Neural Conduction; Reflex; Trigeminal Nerve - physiology; Trigeminal Nuclei - physiology; Trigeminal Nucleus, Spinal - anatomy & histology; Trigeminal Nucleus, Spinal - physiology
• ISSN: 0014-4819
• DOI: 10.1007/BF00231766

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).