Santa Ichikawa

Facilitation of inspiration by intracerebroventricular injection of thyrotropin-releasing hormone in rabbits

Effects of fourth cerebroventricular injection of thyrotropin-releasing hormone (TRH) on respiration were studied in vagotomized rabbits. Phrenic neural activity was recorded and integrated. TRH (1.0 microgram) injection facilitated phrenic neural activity and increased respiratory rate. Peak phrenic nerve activity increased slightly or showed no apparent changes when tonic activity appeared. Tidal phrenic neural activity either increased or decreased, depending on relations between peak phrenic activity and tonic activity. Results suggest that TRH facilitates central respiratory activity to induce tonic activity and increase respiratory rate.

Long term observation of micturition by spinal cord transected rabbits

Neurogenic bladder was observed in chronic spinalized animals. Since these animals are difficult to maintain for long periods, there are few reports of systemic study of these preparations. We have recently observed micturition by spinalized rabbits over a period of 4 weeks. In thoracic or lumbar spinalized rabbits, urinary bladder contraction and external urethral sphincter activity were initially recorded from 1-2 days postoperative. Contraction coincided with appearance of hind-limb spasticity. This micturition was the so-called detrusor-external urethral sphincter dyssynergy with residual urine. In sacral spinalized rabbits, no micturition reflex, external urethral sphincter activity, or hind-limb spasticity were observed and the flaccid state continued for 4 weeks. It is suggested that a segmental micturition reflex pathway exists initially in the rabbit sacral cord, because reappearance of the micturition reflex was extremely quick (1-2 days) compared to that of cats (2-3 weeks). Animal hypnosis enabled immobilization during measurement without anesthetic or decerebration. Chronic spinalized rabbits, which are very intolerant to spinal damage, can be maintained alive by intensive care at and post operation and are useful for systemic study of spinal cord injury.

The effects of high-frequency inflation and high-frequency deflation on respiration in rabbits

High-frequency inflating and deflating triangular pulses of pressure were applied to air in the trachea of urethane-chloralose-anesthetized rabbits. Expiratory time was increased by high-frequency inflation (HFI) and decreased by high-frequency deflation (HFD). Both had little effect on inspiratory time or tidal phrenic nerve activity. HFD provoked more tonic type phrenic activity, with discharges being evident during the expiratory phase. It was demonstrated that HFI, which probably stimulates pulmonary stretch receptors, inhibits the initiation of inspiration and HFD, which probably stimulates irritant receptors, facilitates inspiration.

Demarcation of Ca2+ transport processes in guinea pig stomach smooth muscle

SummaryMicrosomal fractions were isolated from gastric antrum and fundus smooth muscle of guinea pigs. Ca2+ uptake into and Ca2+ release from the membrane vesicles were studied by a rapid filtration method, and Ca2+ transport properties of the different regions of the stomach were compared. ATP-dependent Ca2+ uptake was similar in microsomes isolated from both regions. This uptake was increased by oxalate and was not affected by NaN3. Oxalate affected Ca2+ permeability of both antrum and fundus microsome vesicles similarly. Fundus microsome vesicles preincubated in 100mm NaCl and then diluted to 1/20 concentration with Na+-free medium had significantly higher ATP-independent Ca2+ uptake than vesicles preincubated in 100mm KCl and treated the same way. This was not true for antrum vesicles. Monensin abolished Na+-dependent Ca2+ uptake, and NaCl enhanced Ca2+ efflux from fundus microsome vesicles. The halflife values of Ca2+ loss from fundus vesicles in the presence of NaCl were significantly smaller than those in the presence of KCl. The release of Ca2+ from the vesicles within the first 3 min was accelerated by NaCl to three times that by KCl. However, NaCl had ro effect on Ca2+ release from antrum microsome vesicles.Results suggest two distinct mechanisms of stomach membrane Ca2+ transport: (1) ATP-dependent Ca2+ uptake and (2) Na+−Ca2+ exchange; the latter in the fundus only.

EFFECTS OF ENZYMES ON INTESTINAL SLOW WAVE

Effects of several enzymes on the slow wave of rabbit jejunum were examined. Nagarse, α-chymotrypsin and pronase which are protease reduced the amplitude of slow wave but did not affect on the frequency. Lipase and lysozyme, which catalyze the hydrolysis of triglyceride and mucopolisaccharide, respectively, had no effect on the amplitude and frequency of slow wave. The contributions of proteins, lipids and hydrocarbons in smooth muscle cell membrane to slow wave were discussed.

the action of mebeverine on rabbit colon

1. The spontaneous contraction of the isolated colon was inhibited by mebeverine at doses greater than 1×10-7g/ml. The effect of mebeverine was stronger than that of papaverine or buscopan. Two kinds of movement occur in the rabbit colon, peristaltic movement and the local tonic wave. The local tonic wave is produced mainly by the ring muscle. Papaverine mainly inhibited the peristaltic contractions but the effect of mebeverine and that of buscopan were the inhibition of tonic contractions. These drugs showed greater inhibitory effects on the colonic activity than on the small intestinal one.2. The antispasmodic properties of mebeverine against the evoked contractures yb acetylcholine 10-5 g/ml or BaCl2 10-3g/ml were stronger than those of papaverine and buscopan.3. When mebeverine 10-5g/ml was applied on the isolated colon the spontaneous contractions were enhanced about 50% of the cases. The phasic and tonic contractions were enhanced with the increase of spike discharge. The mechanisn of this phenomenon is obscure.4. When 5mg/kg mebeverine was induced intravenously, the movement of the colon was slightly inhibited. But sometimes colonic movement enhanced, tachycardia appeared, respiration became irregular, tonic convulsion appeared and the animal died. But when mebeverine was given orally no significant alteration of colonic motility was observed.