Cortically evoked rhythmic mastication was variously modified by stimulation of the superior laryngeal nerve and by elicitation of reflex swallowing in rabbits under light ether anesthesia. The recording of the unitary activity was made from motoneurons in the motor nucleus of the trigeminal nerve or from motor fibers in the trigeminal nerve to study the neural mechanism subserving such modification.
1. In the absence of rhythmic mastication, spontaneous activity was consistently present in most masseteric (jaw closing) motor units, but was, however, scarce in the mylohyoid (jaw opener) units.
2. During stimulation of the superior laryngeal nerve, the activity in the masseteric motor units ceased, whereas that in the mylohyoid units discharged a continuous train of impulses.
3. When a swallow was elicited by a squirt of water into the pharynx or by stimulation of the superior laryngeal nerve, there ensued also a silence lasting 250 to 800 msec in the masseteric motoneurons, while a discharge of many impulses lasting 200 to 500 msec occurred in the mylohyoid motoneurons. The duration of these changes in both masseteric and mylohyoid motoneurons depended upon the duration of swallowing which varied with the amount of water or the intensity of stimulus applied.
4. During cortically evoked rhythmic mastication, the masseteric motor units discharged bursts of impulses in phase with jaw closing, whereas the mylohyoid motor units fired with jaw opening. When reflex swallowing was superimposed, the bursts of masseteric units were replaced by silence, while those of mylohyoid units discharged many impulses; and the rhythmic activity of mastication was interrupted.
5. Mechanical stimulation of the oral and pharyngeal mucosa produced a steady discharge of impulses in the mylohyoid motor units, whereas it produced a silence of spontaneous activity in the masseteric motor units.
6. The patterns of activity of the trigeminal motoneurons during rhythmic mastication and their changes both by reflex swallowing and by stimulation of the superior laryngeal nerve persisted after motoparalysis.
7. Based on these findings, the neural organizations involved in the phenomenon and their way of operation are discussed.

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1. Perfusion of isolated carp retina with a pure oxygen saturated standard solution used in this experiment permitted several continuous hours of ERG recordings showing a distinctive b-wave as well as the PIII isolated by sodium aspartate.
2.The dark-adapted threshold for the PIII required an absorption of 5 to 6 quanta per rod.The‘rod-cone break’in the increment threshold curve for the b-wave was induced at a background intensity of about 2.0×10^-2, μW/cm².
3.Both the b-wave and the PIII showed rapid and complete recovery of sensitivity after exposure to dim adapting lights.After bright light adaptation, the sensitivities went through a short‘fast phase’followed by a prolonged‘slow phase’of recovery.The rate of recovery during the fast phase was significantly faster for the PIII than for the b-wave. Neither a lowered temperature (9°C) nor the application of ouabain (10^-6 M) influenced the fast phase.This seems to prove that the visual pigment, photoproducts and the active transport hardly participate in its mechanism, if at all.
4.The prolonged slow phase that followed the fast phase was distinguished by the recovery of the rod activity, even in isolated retinas.

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In urethane-anesthetized rats, single unit recordings were made from intrinsic neurons (I-cells) of the dorsal lateral geniculatenucleus (LGN).
1. Among a total of 434 units recorded, 408 (94.0%) were identified as relay neurons (principal cells, P-cells) and 26 (6.0%) as I-cells. There was found no particular area of the LGN where the sampling ratio of I to P was relatively high or low. Neurons of the perigeniculate reticular nucleus which had previously been taken as the I-cells of the LGN were not encountered in these recordings.
2. The I-cells were fired once by single shock stimulation of the optictract (OT) at the optic chiasm. The latencies ranged from 1.35 to 4.60 msec (mean, 2.60 msec). Calculation with an assumption of monosynaptic excitation indicates that among the three groups of OT fibers with different conduction velocities, the slowest group constitutes an input to the I-cells almost exclusively.
3. In 15 out of 26 I-cells stimulation of the visual cortex caused orthodromic excitation. The threshold intensity was higher than for antidromic activation of the P-cells.
4. By stimulating the OT with double shocks of suprathreshold intensity, the I-cells were found to recover responsiveness within 3 msec after the first excitation.
5. Fifteen I-cells were examined of responses to diffuse light stimulation. Only stimulation of the contralateral eye was effective. The responses were of on-off-type in 8 units, of on-type in 6 units and of off-type in 1 unit.
6. Single shock stimulation of the mesencephalic reticular formation suppressed I-cell's responsiveness to OT stimulation.

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Effect of dantrolene sodium on the activation of potassium contracture in single fibers of frog semitendinosus muscle was studied. Dantrolene shifted the activation curve to the right without changing the depolarization produced by a given K⁺ concentration. The shift of mechanical threshold by dantrolene was dependent on the concentration of calcium in the medium and the effects of dantrolene and Ca⁺⁺ are additive to each other. On the other hand, the action of dantrolene is antagonized by Ca⁺⁺ with respect to the peak tension in 190mM K⁺. In addition, dantrolene did not release ⁴⁵Ca from the self-exchangeable Ca fraction and did not affect the exchange of ⁴⁵Ca in the self-exchangeable Ca fraction with ⁴⁰Ca. It was also observed that dantrolene had no appreciable influence on the ultrastructure of muscle fibers under our experimental conditions. On the basis of these results, the mechanism of action of dantrolene on the activation of excitation-contraction coupling, the relation between the drug and calcium actions and the drugeffect on the Ca movement in T-system membranes were discussed.

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The effect of dantrolene sodium on “inactivation 1 and 2”(see below) of potassium contracture in single fibers of frog semitendinosus muscle was studied. Dantrolene (2.5-10μM) clearly shortened the plateau duration and increased the rate of spontaneous relaxation of the contracture induced by 190mM K⁺, without appreciably affecting the peak tension; we tentatively termed these changes of contracture “inactivation 1.”On the other hand, in the presence of dantrolene at subthreshold K⁺ concentration, the time course of the inhibition of the peak contracture tension induced by 190mM K⁺ was markedly accelerated; we tentatively termed this inhibition “inactivation 2.” Similar results were obtained by dantrolene in the presence of some inactivationfacilitating factors, i. e., in the absence of Ca⁺⁺ or at or low Ca⁺⁺ concentrations, in the presence of 1-3mM procaine, or in the presence of both procaine and K⁺ in subthreshold concentrations (15 and 20mM). From these results, it is suggested that dantrolene has a marked facilitating effect on the mechanical inactivation (“inactivation 1”) which is considered to be related to spontaneous relaxation, whereas it has little effect on another type of inactivation (“inactivation 2”) related to the inhibition of peak tension which changes with time and that dantrolene has a potentiating effect on these two types of inactivations in the presence of the above inactivation-facilitating factors. It was also suggested that the sites of the mechanical inactivation in twitch muscle fibers may be localized at the transverse tubular membrane.

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The half decay time of the K-induced contracture of rabbit main pulmonary artery following pretreatment with Ca-free EGTA containing solution was 110sec. A Ca-free K-solution did not generate contraction while noradrenaline, acetylcholine and prostaglandin F_2α-containing solution did evoke contracture. The decays of the chemically induced mechanical response in Ca-free solution against the exposure times could be classified into three components (2min, 28min and over 100min, respectively).When the membrane depolarization produced by excess K⁺ was simulated in Krebs solution by application of current, the generated mechanical response was smaller than that produced by 118mM K⁺. When the membrane potential was clamped at the resting level before, during and after application of the excess K⁺, and excess K⁺ still evoked contracture. The amplitudes of contracture depended on [K]₀ The effects of various [K]₀ on the length constant of the tissue were also observed in relation to the clamping condition. It is postulated that the mechanical response of the pulmonary artery induced by excess K is mainly due to influx of Ca⁺⁺and the depolarization plays only a minor role. This means that release of stored Ca by depolarization is not an essential factor in generation of K-induced contracture in this tissue.

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The membrane potential of mucous epithelial cells of isolated newt stomach was -23mV on the average at 7°C.The potential decreased when the temperature was lowered further, the normal external solution was replaced with K⁺-free solution, or ouabain or DNP was applied.The decreased membrane potential level of the cells in K⁺- free solution was not changed any more by adding ouabain to the solution. The membrane potential increased transiently beyond the control level when the stomach was returned to the normal solution after being exposed to isotonic NaCl solution with EGTA.The transient potential increase was blocked by ouabain.These results suggest that, even at such a low temperature as 7°, the active ion transport mechanism (s) of mucous epithelial cells in the newt stomach is still capable of functioning to some extent.

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Squid giant axons were intracellularly perfused with a solution containing 100mM K⁺and 5mM tetraethylammonium (TEA) to obtain action potentials with a long-lasting plateau. Effects of intracellular divalent cations on the plateau of the action potentials were examined by introducing 0.1-10mM Ca²⁺, Sr²⁺, Mg²⁺, Ba²⁺, or Mn²⁺ into the perfusate under these conditions. Ca²⁺, Sr²⁺ and Mn²⁺ were found to shorten the plateau duration drastically. Upon removal of the divalent cations in the perfusate, there was a recovery in the plateau duration. The recovery was imperfect in the case of Ca²⁺, nearly perfect in the case of Sr²⁺, and perfect in the case of Mn²⁺. Voltage-clamp experiments carried out on axons intracellularly perfused with the control (i. e., divalent cation free) perfusate revealed the existence of a late inward current through the membrane. Intracellularly administered Mn²⁺ (1-3mM) blocked this late inward current and decreased the membrane conductance during the late period of voltage clamping.Intracellular Mg²⁺ (1-10mM) prolonged the action potential plateau produced by TEA reversibly in some axons; however, this effect was masked by an opposing (i. e., irreversibly plateau-shortening) effect in most axons. Ba²⁺ applied intracellularly prolonged the action potential duration regardless of the presence or absence of TEA in the perfusate. We emphasize that the effects of divalent cations applied internally are very similar to those observed when these cations are applied externally, except that the effective concentration is far lower in the case of internal application. It is suggested that the primary site of action of divalent cations might be on or near the internal surface of the axonal membrane.

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In spontaneously hypertensive rats and normotensive control rats the spinal cord was transected between the vertebrae C7 and Th 1 under ether anesthesia. When the animals recovered from anesthesia in two hours, the blood pressure was significantly higher in the hypertensive rats, indicating that the hypertensive factors are not confined to the supraspinal centers. The blood pressure was also significantly higher in spontaneously hypertensive rats than in normotensive control rats even after pithing the spinal cord below the vertebra of Th 1. In either case subsequent pentobarbital anesthesia abolished the significant difference in pressure between the two groups of rats. The blood pressure after either cord section or pithing tended to increase with age in spontaneously hypertensive rats but not in normotensive control rats. These findings indicate the presence of certain age-dependent peripheral hypertensive factors which are susceptible to pentobarbital and probably myogenic in nature.

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