Toyohiko Satoh

Electrophysiological study on tooth-grinding during sleep

Abstract In order to gain an insight into the central mechanism of tooth-grinding (TG) during sleep, polygraphic recordings were performed on fifteen tooth-grinders. Two hundred and ninety-one episodes of spontaneous TG and 34 episodes of artificially induced TG were observed. The TG commenced at any stage of sleep, but mainly during light sleep. It seldom occurred during deep slow wave sleep, and never during rapid eye movement (REM) bursts of REM sleep. It sometimes occurred on the background of recurring α-waves in drowsy subjects. The termination of TG was usually followed by a sleep stage lighter than that before the episode, and never by a deeper sleep. The episodes of TG were frequently preceded by a K-complex and followed by α-waves. Vasoconstriction of the finger tip and tachycardia were the invariable concomitants of TG. Skin potential changes on the forearm and, less frequently, on the palm were often associated with TG. These changes in the sympathetic activity preceded, in general, the onset of TG. The H-wave was strikingly depressed in amplitude or completely abolished during TG as well as during gross body movements unassociated with TG. Signs of lightening of sleep without gross muscular activities were, in contrast, associated with an increase in the H-wave amplitude. The episodes of TG which could be induced by giving arousing stimuli to sleeping subjects were identical in all their features to the spontaneous episodes. It was concluded that the TG is triggered by an abrupt lightening of sleep and manifests itself during transition from sleep to wakefulness; that is, it appears as an arousal reaction. The hypothetical neuronal mechanisms underlying TG were discussed.

Tissue distribution, developmental profiles and effect of denervation of enolase isozymes in rat muscles

The tissue distribution of muscle-type alpha beta and beta beta enolases in rats were determined with the sandwich-type enzyme immunoassay method which utilized the purified antibodies specific to the alpha and to the beta subunit of enolase, and beta-D-galactosidase from Escherichia coli as label. All the tissues examined contained detectable levels of both alpha beta and beta beta enolases. The beta beta enolase was found at high levels in the skeletal muscle tissues (tongue, esophagus, diaphragm and leg muscles) and in the cartilages (xipoid process and auricular cartilage). The alpha beta enolase was distributed at a relatively high concentration in the heart and in the above-mentioned tissues. The beta beta enolase in the leg muscles, diaphragm and tongue was present on the day of birth at a concentration higher than that of the alpha alpha and alpha beta enolases, and its concentration further increased in a manner apparently related to the functional state of each tissue. Denervation of the leg muscles by cutting the sciatic nerve in adult rats resulted in a drastic change in the isozymes profile. The concentration of beta beta enolase in the tibialis anterior gastrocnemius lateralis and extensor digitorum longus (about 800 pmol/mg protein) decreased to about a half in a few weeks after denervation. In contrast, the concentrations of alpha alpha (2 pmol/mg) and alpha beta (80 pmol/mg) usually showed a slight increase by the treatment (alpha alpha, 7 pmol/mg; alpha beta, 100 pmol/mg after 2 weeks). As compared with these three muscles, the soleus had normally a low enolase level and the effect of denervation was less drastic. These results seem to suggest that the concentration of beta beta enolase is closely correlated with the functional state of the muscle tissue.

Changes in the Concentration of Enolase Isozymes and S‐100 Protein in Degenerating and Regenerating Rat Sciatic Nerve

Levels of enolase isozymes (ãã, ãγ, and γγ forms) and S‐100 protein in rat sciatic nerves were determined during their degeneration and regeneration processes. The sciatic nerves were unilaterally crushed or severed. The rats were killed 1,2,6, and 8‐9 weeks later, and both the proximal and distal portions of the damaged nerves were dissected. Control samples were obtained from the untreated contralateral hindlimbs. Enolase isozymes and S‐100 protein in the nerve segments were determined with the enzyme immunoassay method. The control nerves contained about 40, 90, and 30 pmol/mg protein of ãã, ãγ, and γγ enolases, respectively, and 0.85 μg/mg protein of S‐100 protein. These levels were not affected by repetitive electrical stimulation of the nerve fibers in vivo. The levels of the nervous system‐specific forms of enolase (ãγ and γγ) and S‐100 protein decreased markedly within a week in the distal portion of the crushed nerve (ãγ, 27 pmol/mg; γγ, 5.5 pmol/mg; S‐100 protein, 0.36 μg/mg) with apparently no change in the concentration of aa enolase. These levels in the proximal portion of the crushed nerve remained unaltered. The sensory and motor functions impaired by the sciatic nerve crush showed a recovery more or less after 4‐9 weeks. This recovery was accompanied by a gradual regaining of the specific proteins in the distal portion of injured nerves (ãγ, 64 pmol/mg; γγ, 13 pmol/mg; S‐100 protein, 0.63 μg/mg at the 8‐9th week).

Characterization of the neurons in the region of solitary tract nucleus during sleep.

Abstract Single-unit recording was made from neurons in the region of solitary tract nucleus (NTS) of cats. Neurons discharging in correlation with cardiac or respiratory cycle were identified outside the NTS. They showed no obvious change in discharge rate during sleep-wakefulness cycle, and were unresponsive to electrical stimulation of the mesencephalic reticular formation (MRF), suggesting that they are not involved in slow wave sleep (SS) mechanism. More than half of the neurons recorded in the NTS showed an increase in discharge rate during, but not prior to, SS. Most of non-NTS neurons had during SS a discharge rate similar to that during wakefulness. The NTS neurons may be more related to SS mechanism than non-NTS neurons. The effectiveness of electrical stimulation of the MRF in driving or inhibiting the neurons of the NTS region was measured to be expressed by an index. Generally speaking, responses with greater S/W index ratio were excitatory, while those with smaller were inhibitory. During paradoxical sleep the effectiveness was usually reduced.

Correlated discharges of two neurons in rat gustatory cortex during gustatory stimulation

During application of tastants into the oral cavity correlated activities were observed in 27 of 64 neuron pairs recorded simultaneously in the gustatory cortex of anesthetized rats. The mean frequency of correlated discharges as assessed from the size of the peak appearing in the cross-correlogram was lower (0.2-0.33 spikes/s) and the mean width of the peaks was wider (8 ms) as compared to those reported in the gustatory relay stations in the brainstem. In a few cases troughs were formed or peaks appeared with a long delay.

Relationship between positive sharp wave bursts and unitary discharges in the cat hippocampus during slow wave sleep.

In the cat hippocampus bursts of positive sharp waves (PSWs) appeared sporadically almost exclusively during slow wave sleep. The PSW burst was most often found in cell-rich areas in the CA1 and subiculum, and its occurrence was almost synchronized in different regions. An individual burst was usually composed of 3-5 PSWs of about 10 msec duration and showed a considerable fluctuation in amplitude. It was occasionally followed by a negative-going deflection of large amplitude and long duration (post-PSW negativity). The amplitude of PSWs and post-PSW negativity in the CA1 was high in the area giving a large sized-evoked response after stimulation of the contralateral CA3. The spike discharge rate during the burst was two or three times higher than that during the period just preceding the burst, but the discharge never occurred in the positive phase of the PSWs. During the initial part of the post-PSW negativity the high firing probability was maintained. Even when the PSW burst was not followed by a detectable post-PSW negativity, the firing probability during the period corresponding to the post-PSW negativity was still significantly higher than the pre-PSW period. It was suggested that the PSW bursts and post-PSW negativity were triggered off in cell-rich areas by diffuse excitatory inputs impinging possibly upon the hippocampal pyramidal cells and subicular principal cells. The rhythmic PSWs may be post-synaptic inhibitory potentials produced on the somata of those cells after activation of recurrent interneuronal circuits.

Muscle-specific β-enolase concentrations after cross- and random innervation of soleus and extensor digitorum longus in rats

The concentration of beta-enolase, a highly specific marker of the skeletal muscle of rats, was determined in a slow-twitch muscle, the soleus (SOL) and a fast-twitch muscle, the extensor digitorum longus (EDL) after cross-innervation, random reinnervation, or denervation. The beta-enolase concentration is normally high in EDL and low in SOL. When the nerves entering into these muscles were cross-sutured, the beta-enolase concentration in EDL decreased and that in SOL increased to reach an almost equal value in 20 weeks and by the 35th week the SOL ultimately had a higher beta-enolase concentration than the EDL. When the sciatic nerve trunk was completely transected and sutured immediately, the beta-enolase concentration in EDL decreased and that of SOL increased; in 20 weeks SOL had a beta-enolase concentration similar to that of the EDL. When these muscles were denervated by cutting the sciatic nerve trunk, their beta-enolase concentrations were markedly lowered, but EDL still retained on the 12th week a beta-enolase value comparable to the normal SOL. Possible mechanisms behind the observed changes in beta-enolase concentration are discussed.

Depression of the H-reflex during tooth grinding in sleep

Abstract During tooth grinding the H-wave was always depressed in amplitude or abolished. Any gross body movement during sleep, unassociated with tooth grinding, also induced a similar depression of the H-wave. It was concluded that, in terms of the influence on the H-reflex arc, tooth grinding is equivalent to gross body movements commonly observed during an abrupt lightening of sleep.

Modulation during sleep of the cat trigeminal neurons responding to tooth pulp stimulation

Sleep-induced changes in the trigeminal neuron responses to electrical stimulation of the cat tooth pulp were studied. Two parameters were adopted: One was the evoked spike number at two times the threshold intensity (2 X T response magnitude), which would reveal the level shifting of the neuronal response by the sleep-regulatory system. Another was the rate of change in the response intensity when the stimulus was raised to a level of 0.7 time the arousal threshold during light slow wave sleep (sensitivity gradient), which would reflect the influences of the pain-modulatory system driven by strong noxious inputs. It was found that during sleep the two indexes tended to show a correlated change; the neurons which came to have a greater 2 X T response magnitude tended to have a smaller sensitivity gradient than during wakefulness, and vice versa. It was suggested that two contrasting populations of tooth pulp neurons might be differentiated, and that the sleep-regulatory system and the pain-modulatory system would have differential but correlated controls over these two kinds of neurons.

Functional relationship between cat brainstem neurons during sleep and wakefulness.

Abstract The mode of interaction between so-called sleep-wakefulness centers in the cat lower brainstem was studied on 100 neurons. The magnitude of the spike response of a neuron in one center to electrical stimulation of another center was measured to calculate the index of responsiveness. During REM sleep the index was, in a great majority of cases, significantly smaller as compared with that during wakefulness and slow wave sleep. This reduction in the effectiveness of information transmission between different centers might be the basis of characteristic events occurring during REM sleep. From the behavior of the indexes during sleep-wakefulness cycle, it is suggested that different phases of sleep and wakefulness are realized by a complicated interplay of many sleep-wakefulness centers which would be communicating with one another not only through channels which are activated in a phase-specific manner, but also through a larger number of channels of which activity is modulated differentially during different phases.