Summary
Seventy-one (n = 71) premotor interneurones have been localized by extracellular recordings within the subnucleus-γ of the oral nucleus of the spinal trigeminal tract (NVspo-γ) in nineteen chloralose anaesthetized cats. The neurons were antidromically activated by microstimulation (minimum = 3μA) applied to the digastric motoneurone subnucleus of the trigeminal motor nucleus. Fifty-one (n = 51) of the interneurones were discharged from the ipsiand 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-γ 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-γ (Westberg and Olsson 1991).
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Abbreviations
- AD:
-
Antidromic
- Alv inf:
-
Inferior alveolar nerve
- Co:
-
Contralateral
- D:
-
Dorsal
- Dig:
-
Digastric nerve
- Fp:
-
Focal potential
- m Dig:
-
Digastric muscle
- Ggl V:
-
Trigeminal ganglion
- Ip:
-
Ipsilateral
- Ling:
-
Lingual nerve
- M:
-
Medial
- Mass:
-
Masseteric nerve
- Mn:
-
Mandibular nerve
- Mx:
-
Maxillary nerve
- Mxw:
-
Maxillary nerve, branch to whiskers and lip
- O:
-
Opthalmic nerve
- NVmt-dig:
-
Digastric subnucleus of the trigeminal motor nucleus
- NVsnpr:
-
Main sensory trigeminal nucleus
- NVspo-γ :
-
Subnucleus-γ of the oral nucleus of the spinal trigeminal tract
- OD:
-
Orthodromic
- V:
-
Trigeminal tract
- VII:
-
Facial nerve
- Vrm:
-
Trigeminal motor root
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Olsson, K.Å., Westberg, KG. Integration in trigeminal premotor interneurones in the cat. Exp Brain Res 84, 115–124 (1991). https://doi.org/10.1007/BF00231766
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DOI: https://doi.org/10.1007/BF00231766