Fictive Mastication Research Articles

Discharge patterns of trigeminal commissural last-order interneurons during fictive mastication in the rabbit

1. The aim of these experiments was to examine the physiological properties and patterns of firing of trigeminal interneurons during fictive mastication in anesthetized and paralyzed rabbits. Antidromic stimulation was used to show that the 82 interneurons projected to the area of the contralateral fifth nerve motor nucleus (NVmot). 2. Straight-line conduction velocities calculated from stereotaxic coordinates of the stimulating and recording electrodes for 63 interneurons were found to range between 3.7 and 16.3 m/s (mean, 9.5 m/s). 3. Histological reconstructions of recording electrode tracks showed that the interneurons observed in this study were located in the lateral brain stem in or just medial to the rostral trigeminal sensory nuclei, including the intertrigeminal (NVint) and supratrigeminal (NVs) areas, the main sensory nucleus of the fifth nerve (NVsnpr), the rostral subdivision of the oral nucleus of the spinal trigeminal tract (NVor tau), and the rostral part of the parvocellular reticular nucleus (NRpc alpha). 4. Forty-six interneurons were shown to have low-threshold (LT) peripheral receptive fields, and 41 of these (88%) were in the oral cavity. Most of the responses were rapidly adapting. 5. Twenty-eight interneurons changed their pattern of firing during cortically induced fictive mastication. The discharge frequency of 20 neurons varied in phase with the fictive masticatory motor output, which was recorded from central ends of cut hypoglossal nerves (XII) and/or from the NVmot. Others were briefly excited and then inhibited (n = 2), only inhibited (n = 4), or tonically excited during fictive mastication (n = 2). Fifteen others were unaffected by this test. 6. It was found that the rhythmically active neurons could be further subdivided into two categories: those receiving short-latency excitatory input from the masticatory area of the cortex (n = 11) and those that did not (n = 9). No obvious differences in peripheral receptive fields for neurons in these categories were found. 7. We suggest that these phasically active premotor neurons are part of the circuitry generating the rhythmic masticatory pattern, specifically those that directly control the bursts of firing of the trigeminal motoneurons (burst generators, BGs). Their properties allow them to integrate sensory information and descending commands with the masticatory rhythm that is probably generated in midline brainstem reticular nuclei.

Modulation of activity of spindle afferents recorded in trigeminal mesencephalic nucleus of rabbit during fictive mastication

1. These experiments were based on the findings that antidromic firing is observed in first-order sensory afferents during fictive locomotion and were designed to test the hypothesis that a similar central modulation of afferent discharge occurs during mastication. To do this, spindle afferents were recorded in the trigeminal mesencephalic nucleus (Mes V) of anesthetized and paralyzed rabbits during fictive mastication. The cortical masticatory area was stimulated to induce mastication, and activity of the XIIth or the Vth nerves were recorded to monitor the masticatory motor rhythm. 2. Although we could find little evidence that antidromic discharges invade the somatic region of this class of sensory afferents, we did discover a previously unrecognized type of modulation of afferent firing. 3. Of 83 slowly adapting muscle spindle afferents, 33 were modulated during fictive mastication. In 28 cases, the modulation consisted of a phasic inhibition, whereas for the remaining units it could be either a phasic excitation (n = 2) or an excitation alternating with an inhibition (n = 3). 4. Rapidly adapting units were also tested when encountered. Tonic or phasic excitation was never observed. The presence of inhibition could not be verified for this population because tonic activity could not be maintained by passive stretch. 5. The main electroneurogram (ENG) burst of the XIIth and Vth cranial nerves occurred during the opening phase of the masticatory cycle, and in all cases where the records were clear (22 out of 33), phasic inhibition of the afferents coincided with the ENG burst. 6. There was no difference in the distributions of the modulated and of the unmodulated units along the length of the Mes V nucleus. 7. Approximately 40% of trigeminal spindle afferent cell bodies have dendrites, and we suggest that these are the ones rhythmically modulated during fictive mastication. The possible role of this modulation is discussed.

Synaptic bases of cortically-induced rhythmical hypoglossal motoneuronal activity in the cat

Intracellular recordings were made from hypoglossal motoneurons during cortically-induced fictive mastication in paralyzed encéphale isolé cats. Repetitive stimulation of the masticatory area of the cerebral cortex induced rhythmical tongue movements coordinated with jaw movements. After the animal was immobilized, the cortical stimulation still induced rhythmical burst activities in the hypoglossal nerve and the digastric nerve. The burst activities in the medial and lateral branches of the hypoglossal nerve alternated rhythmically, and were in and out of phase with the burst activities of the digastric nerve, respectively. All hypoglossal motoneurons showed rhythmical intracellular potentials during repetitive cortical stimulation. The rhythmical depolarizing potentials superimposed by spike bursts appeared in phase with rhythmical bursts in either the lateral or medial branch of the hypoglossal nerve. No hyperpolarization was present between consecutive depolarizing potentials. Synaptic activation noise increased coincidentally with the depolarizing potential, indicating that EPSPs were involved in the generation of the depolarizing potential. No evidence was obtained for the existence of IPSPs during the inter-depolarizing phase by intracellular current injection. It was concluded that rhythmical bombardment of excitatory impulses to hypoglossal motoneurons was responsible for the rhythmical activity induced by repetitive stimulation of the cortical masticatory area.

Phase-linked modulation of excitability of presynaptic terminals of low-threshold afferent fibers in the inferior alveolar nerve during cortically induced fictive mastication in the guinea pig

Excitability of presynaptic terminals of low-threshold primary afferent fibers in the inferior alveolar nerve was tested in the trigeminal spinal nucleus of the ketamine-anesthetized, paralyzed guinea pig, by Wall's method. Fictive mastication was induced by repetitive stimulation of the cortical masticatory area, and was monitored by rhythmical burst activity in the jaw-opening anterior digastric motoneuron pool. The excitability was rhythmically modulated in a phase-linked manner during the masticatory cycle: it was decreased coincidentally with the digastric burst activity (jaw-opening phase) and increased during the middle and late periods of the interburst phase (jaw-closing phase) of the masticatory cycle. The results imply that presynaptic modulation of synaptic transmission of peripheral inputs from primary afferents to interneurons in the jaw-opening reflex pathway may contribute to the rhythmical modulation of the jaw-opening reflex evoked by innocuous stimulation of the intraoral structures during mastication; presynaptic inhibition contributing to the depression of the jaw-opening reflex during the jaw-closing phase and presynaptic facilitation to its enhancement during the jaw-opening phase.

The modulation of sensory transmission through the medullary dorsal horn during cortically driven mastication.

During mastication, reflexes are modulated and sensory transmission is altered in interneurons and ascending pathways of the rostral trigeminal sensory complex. The current experiment examines the modulation of sensory transmission through the most caudal part of the trigeminal sensory system, the medullary dorsal horn, during fictive mastication produced by cortical stimulation. Extracellular single unit activity was recorded from the medullary dorsal horn, and multiple unit activity was recorded from the trigeminal motor nucleus in anesthetized, paralyzed rabbits. The masticatory area of sensorimotor cortex was stimulated to produce rhythmic activity in the trigeminal motor nucleus (fictive mastication). Activity in the dorsal horn was compared in the presence and absence of cortical stimulation. Fifty-two percent of neurons classified as low threshold and 83% of neurons receiving noxious inputs were influenced by cortical stimulation. The cortical effects were mainly inhibitory, but 21% of wide dynamic range and 6% of low threshold cells were excited by cortical stimulation. The modulation produced by cortical stimulation, whether inhibitory or excitatory, was not phasically related to the masticatory cycle. It is likely that, when masticatory movements are commanded by the sensorimotor cortex, the program includes tonic changes in sensory transmission through the medullary dorsal horn.

Single unit activity in lateral reticular nucleus during cortically evoked masticatory movements in rabbits

The activity pattern of the lateral reticular nucleus (LRN) neurones was analyzed during cortically evoked masticatory movements in anesthetized rabbits. Antidromic activation from the cerebellum and histological reconstruction of recorded neurones location from electrode tracks and microdrive readings were the criteria for neuronal identification. Tonic changes as well as rhythmic modulation of neuronal activity were found in a subpopulation of LRN cells during mastication. The same results were observed also in curarized rabbits during fictive mastication. These data support the view that LRN neurones are involved in a central mechanism controlling the masticatory movements.

Phase-linked variations in the amplitude of the digastric nerve jaw-opening reflex response during fictive mastication in the rabbit.

The diagastric nerve reflex response to stimulation of the upper lip was studied in urethan-anesthetized rabbits paralysed with pancuronium bromide. Rhythmic bursts of masticatory activity were evoked in the nerve by repetitive electrical stimulation of the motor cortex. The amplitude and latency of the reflex responses during fictive mastication were compared with preceding control values. When stimuli close to threshold were given, the largest and earliest responses occurred during the digastric burst. When intense stimuli were employed, the largest responses were out of phase with the burst, although the latency was still shortest when the motoneurons were rhythmically active. Since the pattern is essentially the same as that seen during normal mastication, we conclude that the cyclical modulation of reflex amplitude and latency is not the result of sensory feedback generated by the movements themselves but is instead governed by the central motor program.

Intracellular analysis of synaptic mechanisms controlling spontaneous and cortically induced rhythmical jaw movements in the guinea pig.

Intracellular analysis of synaptic mechanisms controlling spontaneous and cortically induced rhythmical jaw movements in the guinea pig.S H Chandler, and L J GoldbergS H Chandler, and L J GoldbergPublished Online:01 Jul 1982https://doi.org/10.1152/jn.1982.48.1.126MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByInvolvement of histaminergic inputs in the jaw-closing reflex arcChikako Gemba*, Kiyomi Nakayama*, Shiro Nakamura, Ayako Mochizuki, Mitsuko Inoue, and Tomio Inoue9 June 2015 | Journal of Neurophysiology, Vol. 113, No. 10Development of Inward Rectification and Control of Membrane Excitability in Mesencephalic V NeuronsSusumu Tanaka, Nanping Wu, Chie-Fang Hsaio, Jack Turman, and Scott H. Chandler1 March 2003 | Journal of Neurophysiology, Vol. 89, No. 3Multiple Effects of Serotonin on Membrane Properties of Trigeminal Motoneurons In VitroC. F. Hsiao, P. R. Trueblood, M. S. Levine, and S. H. Chandler1 June 1997 | Journal of Neurophysiology, Vol. 77, No. 6Immunohistochemical localization of glutamate and glutaminase in guinea pig trigeminal premotoneuronsBrain Research, Vol. 634, No. 1Diverse firing properties of single motor units in the inner and outer portions of the guinea pig anterior digastric muscleArchives of Oral Biology, Vol. 38, No. 2Monosynaptic connections between neurons of trigeminal mesencephalic nucleus and jaw-closing motoneurons in the rat: an intracellular horseradish peroxidase labelling studyBrain Research, Vol. 559, No. 2Effects of lingual nerve and chewing cortex stimulation upon activity of the swallowing neurons located in the region of the hypoglossal motor nucleusBrain Research, Vol. 548, No. 1-2Mastication and its Control by the Brain Stem1 December 2016 | Critical Reviews in Oral Biology & Medicine, Vol. 2, No. 1The effects of nanoliter ejections of lidocaine into the pontomedullary reticular formation on cortically induced rhythmical jaw movements in the guinea pigBrain Research, Vol. 526, No. 1Effects of chewing frequency and bolus hardness on human incisor trajectory and masseter muscle activityArchives of Oral Biology, Vol. 35, No. 4Evidence for excitatory amino acid transmission between mesencephalic nucleus of V afferents and jaw-closer motoneurons in the guinea pigBrain Research, Vol. 477, No. 1-2Synaptic bases of cortically-induced rhythmical hypoglossal motoneuronal activity in the catNeuroscience Research, Vol. 5, No. 5Phase-linked modulation of excitability of presynaptic terminals of low-threshold afferent fibers in the inferior alveolar nerve during cortically induced fictive mastication in the guinea pigBrain Research, Vol. 446, No. 1Cortically induced masticatory rhythm in masseter motoneurons after blocking inhibition by strychnine and tetanus toxinNeuroscience Research, Vol. 4, No. 5Neural basis for initiation of rhythmic digastric activity upon midbrain stimulation in the guinea pigBrain Research, Vol. 411, No. 1A hierarchy of neural control of mastication in the ratNeuroscience, Vol. 19, No. 2Effects of a serotonin agonist and antagonist on cortically induced rhythmical jaw movements in the anesthetized guinea pigBrain Research, Vol. 334, No. 2The relationship between cortically induced mandibular movements and lateral pterygoid and digastric muscle EMG activity in the anesthetized guinea pigBrain Research, Vol. 329, No. 1-2Peripheral influences on the central pattern-rhythm generator for tongue movements in the ratArchives of Oral Biology, Vol. 30, No. 5The effects of a glycine antagonist (strychnine) on cortically induced rhythmical jaw movements in the anesthetized guinea pigBrain Research, Vol. 325, No. 1-2The effects of orofacial sensory input on spontaneously occurring and apomorphine-induced rhythmical jaw movements in the anesthetized guinea pigNeuroscience Letters, Vol. 53, No. 1Differentiation of the neural pathways mediating cortically induced and dopaminergic activation of the central pattern generator (CPG) for rhythmical jaw movements in the anesthetized guinea pigBrain Research, Vol. 323, No. 2Masticatory movements and EMG activity following electrolytic lesions of the trigeminal motor nucleus in growing guinea pigsAmerican Journal of Orthodontics, Vol. 86, No. 2Masticatory muscle activities during rhythmic jaw movement associated with tooth contact in lightly anesthetized ratsExperimental Neurology, Vol. 85, No. 1Activity during active sleep of bulbar reticular neurons firing rhythmically during mastication in catsExperimental Neurology, Vol. 85, No. 1Characterization of synaptic potentials in hindlimb extensor motoneurons duringl-DOPA-induced fictive locomotion in acure and chronic spinal catsBrain Research, Vol. 303, No. 1 More from this issue > Volume 48Issue 1July 1982Pages 126-38 https://doi.org/10.1152/jn.1982.48.1.126PubMed7119841History Published online 1 July 1982 Published in print 1 July 1982 Metrics