On the excitation and inhibition of the inspiratory neuron in the respiratory centers

In decerebrated cats the impulse discharges were detected by means of an unipolar microelectrode from a single inspiratory neuron in the respiratory centers, and the change in discharge produced by administration of stimulating, as well as depressant agents, was studied. The results were summarized as follows. 1) Inhalation of the air containing all. excess of carbon dioxide, as well as the air deficient of oxygen and the intravenous administration of a small dose of caffeine, aminocordine and lobeline produced a) a remarkable increase of frequency of impulses in the stage of constant frequency of the volley, b) a rapid increase of frequency of impulses in the stage of crescent frequency of the volley and c) a shortening of the duration of the volleys, as well as of silent periods. 2) In narcosis by a moderate dose of morphine, as well as in the recovery stage from apnea produced by over-ventilation, there were observed the phenomena which were exactly opposite to those described in 1). 3) It was concluded that a most essential sign by which one can discern whether the activity of the respiratory Genters is raised or depressed, is the changes of the frequency of impulses produced from an inspiratory neuron. The expense of this research was defrayed from the grant in aid of the Ministry of Education.</p

On the Behavior of the Respiratory Muscles During Vomiting

In order to produce vomiting in the dogs decerebrated and unanesthetized, apomorphine or copper sulfate was administered. The behaviors of both the inspiratory and the expiratory muscles were studied through the course of the act of vomiting by the electromyographic technique. The results are summarized as follows: (1) The most significant signs of vomiting seems to be the recurrent vomiting volleys from the vomiting center each of which is produced abruptly and transiently. (2) The peculiarities of the vomitng volley consist in the simultaneous discharges of both the inspiratory and the expiratory muscles, resulting in the so-called retching movement. (3) The vomiting volleys, in their rhythm, seem to arise independent of the respiratory center, but the former are capable of affecting the respiratory centers at any respiratory phase. (4) The acceleration of the breathings observed prior to the retching seems to be due to the invigorated activity of the respiratory centers affected directly by the administration of the vomiting agents without an intermediate step by the vomiting centers. (5) The simultaneous contraction of the diaphragm and the abdominal muscles are merely a component of a peculiar type of the respiratory movements, namely, that of the retching. (6) The glottis muscles are, however, ruled out from the principle described in (2): the closer of the glottis muscles contracts during the retching, while the opener is completely inhibited.</p

The action of atropine and acetylcholine on the pace maker ganglion cells of limulus heart

On the median nerve trunk-heart muscle preparation of Limulus the authors studied the effects of atropine and acetylcholine upon the pace maker ganglion cells. The results are summarized as follows: (1) Atropine exerts an excitatory action on the pace maker ganglion cells in a concentration of 1-2 per cent. resulting in an increase of the heart rate. No effect is recognized on the heart beats, where the drug is applied to the heart muscle. (2) Acetylcholine exerts an excitatory action in a lower concentration (0.001-0.10 %) and produces a transitory excitation followed by an inhibition in a higher concentration (1-5 %). No effect is perceptible on the heart beats, when the drug is applied to the heart muscle. (3) Where atropine has been previously applied to the median nerve trunk, acetylcholine applied to the same spot produces always an inhibition of the heart beats. Conversely, when the ganglion cells activated previously by acetylcholine, a subsequent administration of atropine suppresses the activity of the ganglion cells, resulting in an inhibition of the heart beats.</p

Automatic activies of the spinal cord concerned with the respiratory movements

1. After spinal transection at the medulla-spinal junction the thoracic respiratory movements no longer appear in the adult animals, nevertheless the sporadic spike discharges can be recorded from the intercostal muscles. 2. Both in the acute and chronic experiments the spinal cord is transected at the two levels of Th7 and Thl1 respectively and all the dorsal rootlets coming into that part of the cord lying between the transections are severed. The sporadic spike discharges with irregular intervals varying about 0.5 to 3.0 sec. can be recorded from intercostal muscles in the 8th to 10th segments of the spinal cord isolated. There can never be found any reflex influence of the skin stimulation upon the discharges, which also disappear provided the intercostal nerves innervating the muscles are severed. 3. From these results it may be concluded that the spinal cord is endowed with an ability to initiate the impulses autochthonously to excite the intercostal muscles, even though it is only poorly developed in the adult animals.</p

A Factor Condition­ing the Inhibitory Response of the Intestinal Motility to the Peripheral Stimulation of the Cervical Vagus Nerves

Recording the motility of the stomach as well as the small intestine by the balloon method in the dogs decerebrated and unanesthetized, we found a factor conditioning the inhibitory effect of the intestinal motility to the stimulation of the perpheral cut-end of cervical vagus nerves. The results may be summarized as follows: (1) The stimulation of the peripheral cut-end of the cervical vagus nerve frequently produces the yarious patterns and degrees of inhibition of the intestinal motility of the stomach as well as of the small intestine. (2) The inhibitory effect still appears after the severing of the vagus nerves at the caudal end of the esophagus, but is obliterated and reversed to the augmentory when the splanchnic nerves are bilaterally severed. (3) The cause of the inhibition is attributable to the strong excitation of the intestinal inhibitory centers brought about by the central stimulating action of the anoxemia resulting from the stimulation of the cervical vagus nerves, and the reversal of the response is due to the peripheral stimulating action of the anoxemia upon the intestinal muscles, its central action being excluded from the action on the intestine by the severing of the splanchnic nerves.</p

On the intestinal extrinsic reflexes elicited from the small in­testine

Effects of stimulation of the small intestine upon the gastric, small intestinal and colonic motility have been studied in dogs. The results are summarized as follows. 1. The movements of the stomach, small intestine, and proximal colon are always inhibited by the distension or the contracture of the muscular coats of the small intestine but no responses are produced by a mechanical or chemical stimulation of the mucosa; and those of the distal colon are in most cases also inhibited, whereas in rare instances are they augmented. 2. The afferent impulses are transmitted through the great and small splanchnic nerves and the lumbar sympathetic nerves to the inhibitory as well as the excitatory (pelvic nuclei) centers of the intestinal movements located within the spinal cord, whereas the vagal nuclei remain unaffected. The efferent impulses are transmitted through the thoraco-lumbar sympathetic nerves as well as through the pelvic nerves. The latter are involved in the augmentative effect produced in the distal colon. 3. The threshold producing the extrinsic muscular reflex is higher than that eliciting the intrinsic muscular reflex.</p

The effect of intraluminal pressure upon the frequency of intestinal contraction waves.

In guinea pigs the lumen of an excised jejunal segment was perfused to study the effect of intraluminal pressure on the frequency of rhythmic contraction waves. Within the range of 0 to 40 mmH2O, increases in intraluminal pressure caused increases in the frequency of contraction waves. At pressures of 10, 15, 20, 30 and 40 mmH2O the frequency was 7.9, 9.0, 10.9, 12.5 and 13.3 per min (mean of ten preparations), respectively. An exponential relationship was proved to exist between the pressure and the frequency.</p