Masaya Funakoshi

Periodontal Jaw Muscle Reflexes in the Albino Rat

Pressing or tapping stimulation on the maxillary incisor activated the jaw muscles, especially the masseter muscle, in an anesthetized albino rat. Periodontal jaw muscle reflexes involved two reflex pathways passing through the mesencephalic tract nucleus and the main sensory nucleus of the trigeminal nerve. The mechanoreceptors in periodontal ligaments contributed to an increase in the jaw muscle activity.

A role of oral afferents in aversion to taste solutions

Abstract Relationships between drinking behavior and electrical responses of the chorda tympani and lingual nerves were investigated in albino rats. An unacceptable concentration of quinine hydrochloride solution was 0.14–0.2% w/v, and that of tartaric acid was 4–8% w/v. Daily intakes of quinine hydrochloride and tartaric acid solutions decreased in proportion to the increase of the magnitude of neural response of the chorda tympani. Sucrose solutions were acceptable in all concentrations. The most acceptable concentration was about 10% w/v. Neural responses of the chorda tympani to sucrose solutions increased exponentially as the concentration was increased. The most acceptable concentration of sodium chloride solution was 1–2% w/v. Unacceptable concentrations were 6–8% w/v and greater. Responses of the chorda tympani increased exponentially as the concentration was increased. A few fibers in the lingual nerve which responded to mono-valent but not di-valent salt solutions in high concentration were found in rat. The role of these nerves in aversion to strong salt solutions was discussed.

Effects of the Tonic Neck Reflex on the Jaw Muscles of the Rat

Effects of the tonic neck reflex on the jaw muscles were studied in rats with both ear labyrinths destroyed immediately after decerebration. Electric activities of the jaw muscles increased or decreased in response to rotation, tilting, and flexion of the head. The electromyographic responses to head position were abolished after the first three cervical nerves were cut. We concluded that the tonic neck reflex has an influence on the jaw muscles.

A possible brain mechanism for rejection behavior to strong salt solution.

Abstract Rats accept about 1 per cent sodium chloride in larger quantity than any other concentrations and reject about 6 per cent sodium chloride. The preference and aversion behavior to salt solution were abolished after bilateral ablation of the cortical taste area. Daily intake of 1 per cent sodium chloride increased markedly after bilateral lesions of the ventromedial (VM) hypothalamus of the rat, and even 6 per cent sodium chloride was accepted a little. When the rat drunk 1 per cent sodium chloride, EEG of the lateral hypothalamus was activated, and EEG of the medial hypothalamus was activated by application of 6 per cent sodium chloride to the tongue. Evoked potentials from the medial hypothalamus, induced by electrical stimulation of the tongue, were abolished after ablation of the cortical taste area. Spontaneous unit discharges of the lateral part of the posterior hypothalamus were inhibited by application of 6 per cent sodium chloride to the tongue surface, while spontaneous unit discharges of the medial part of the posterior hypothalamus were activated when 6 per cent sodium chloride was applied to the tongue. A possible brain mechanism of the linguo-cerebro-hypothalamic system for aversion behavior to strong salt solution were discussed.

ACTIVITIES OF THE SENSORY NERVE FROM THE SUBMANDIBULAR GLAND IN A DOG.

It is well known that the salivary glands are innervated by the autonomic secretary and vasomotor nerve, and the possibility of an existence of the sensory nerve fibers distributed from the salivary gland may also be considered morphologically. In this experiment, physiologic characters of the sensory nerve from the gland were studied by means of a neurophysiologic method, and the physiologic function of this nerve was also analyzed. Anesthetized dogs were used. A small polyethylene tube was inserted into the duct of the submandibular gland, and the other Y-shaped end of the tube was connected to a balloon pump (pressure

Effects of brain extracts on activity of the trigeminal motor and hypoglossal nuclei.

Alterations in trigeminal motor and hypoglossal nuclei discharges were noted following microinjections of ethanol and saline brain tissue extracts, ACh and γ-aminobutyric acid (GABA). Background activities of these nuclei were not affected by microinjection of 0.9% saline solution or tris buffer [tris (hydroxymethyl) amino methane] of pH 7.2. Solutions of pH 8.5 (tris buffer) or pH 5.8 (glycine buffer) gradually inhibited these discharges. Spontaneous discharges of the trigeminal motor nuclei were accelerated by the saline extract of the brain tissue and ACh, and they were inhibited by the ethanol extract of the brain tissue and GABA. Discharge of this nucleus accelerated by lower jaw depression was also inhibited by the ethanol brain extract and GABA. Background activity of the hypoglossal nuclei was mildly accelerated by the saline brain extracts and ACh, greatly accelerated by the ethanol brain extracts, and strongly inhibited by GABA. The saline extract of the brain tissue extracted from brain stem had a stronger activator than that extracted from cortical tissue.