Yoshida, M. and Koeda, T. Effects of aminobenzyl penicillin (AB-PC), methyl-chlorophenyl isoxazolyl penicillin (MCI-PC) and 6-aminopenicillanic acid (6-APA) on the contractile response of guinea-pig urinary bladder. Japanese Journal of Smooth Muscle Research, 1984, 20 (1), 1-12. The present study was undertaken to investigate the effects of aminobenzyl penicillin (AB-PC), methylchlorophenyl isoxa-zolyl penicillin (MCI-PC), and 6-aminopenicillanic acid (6-APA) on the contractile response of guinea-pig urinary bladder. AB-PC, MCI-PC, and 6-APA, respectively, diminished the intramural electrical stimulation-induced contractile response. AB-PC had almost no effect on the contractile response to exogenous acetylcholine, while MCI-PC remarkably reduced it. The reducing effect of MCI-PC was greater on the intramural electrical stimulation-induced contractile response than it is on the exogen-ous acetylcholine-induced contractile response. 6-APA slightly reduced the exogen-ous acetylcholine-induced contractile response. The reducing effect of 6-APA was a little weaker on the exogenous acetylcholine-induced contractile response than it is on the intramural electrical stimulation-induced contractile response. By the addition of AB-PC, the amplitude of spontaneous contractile response of the tissue was reduced gradually with slight lowering of the tonus level of the tissue. By the addition of MCI-PC, the spontaneous contractile response of the tissue was almost prevented with a little lowering of the tonus level of the tissue. The effects of AB-PC and MCI-PC on the spontaneous contractile response of the tissue mentioned above were also observed in the presence of tetrodotoxin. On the other hand, by the addition of 6-APA, the reducing effect on the amplitude of spontaneous contractile response of the tissue and increasing effect on its frequency were recognized with remarkable raise of the tonus level of the tissue. These phenomena which were induced by 6-APA were also observed in the presence of tetrodotoxin. From these results, the conclusion comes as follows: 1) AB-PC may affect not only on the muscle but also on the intramural cholinergic nerves. 2) MCI-PC may affect on the muscle, but its effect on the intramural nerves is also not likely to be negligible at this time. 3) 6-APA may affect mainly on the muscle.

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Simultaneous 24hrs' polygraphic recording of the electrical potentials and the contractions of the stomach and duodenum was done in the unanesthetized state of mongrel dogs with chronically implanted electrodes and their interrelationship between these two organs was studied. The results obtained were as follows:
1) In contrast to the diurnal rhythm of gastric activity after feeding, the frequency of the duodenal basic electric rhythm (BER) once increased immediately after feeding and thereafter gradually decreased during the fed state. A negative correlation was found with statistical significance between the frequencies of the gastric and duodenal BERs during the fed state.
2) Tachygastria exhibiting the high frequency BER appeared in the antrum at the silent period of the fasting state, while any similar phenomena were not observed in the duodenum.
3) In the fasting state, the interdigestive migrating contraction (IMC) occurred periodically and synchronously with each other of the two organs. Regarding each contraction, the duodenal contraction was inhibited at a strong contraction of the stomach.
These results suggest that the BERs of the stomach and duodenum are not directly propagated to each other and that some reciprocal interaction between the two organs may come out in the fed state probably by reflexes via intramural nerve plexuses.

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Sunano, S. Stimulating and potentiating effects of sodium nitroprusside on the guinea-pig was deferens and their comparison with the effects on the portal vein and the taenia coli. Japanese Journal of Smooth Muscel Research, 1984, 20 (1), 25-33.-The effects of sodium nitroprusside on the electrical and mechanical properties of the guinea-pig was deferens were studied and compared with those on the portal vein and the taenia coli. Sodium nitroprusside at concentrations higher than 0.5mM caused depolarization of the membrane of the was deferens and initiated spontaneous contrac-tions, while spontaneous contractions of the portal vein were blocked by similar concentration of the drug. Noradrenaline-and carbachol-induced contractions of the was deferens were markedly potentiated by sodium nitroprusside, whereas the nora-drenaline-induced contraction of the portal vein was suppressed by the same concentration of the drug. Increasing the K⁺ concentration by 15 to 30mM caused a similar potentiation of the contraction by noradrenaline or carbachol in the was deferens.
When sodium nitroprusside was applied during the course of noradrenalineor carbachol-induced contracture, contraction was observed in the was deferens, while relaxation was induced in the portal vein and taenia coli. In either case, however, the addition of Ca caused a relaxation of the preparations.
These results suggest that the membrane depolarization may be involved in the stimulating effects sodium nitroprusside in the guinea-pig was deferens.

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Sunano, S. The effects of sodium nitroprusside on the phasic and tonic contraction of the potassium contracture of the smooth muscle of guinea-pig was deferens and portal vein. Japanese Journal of Smooth Muscle Research, 1984, 20 (1), 35-43.- The effects of sodium nitroprusside on potassium-induced phasic and tonic contraction of the guinea pig was deferens and portal vein were studied. Sodium nitroprusside at concentrations higher than 10^-4M potentiated the phasic contraction of potessium contracture of the was deferens, while it showed no or slight depressing effect on the tonic contraction. Sodium nitroprusside at the same concentration depressed both the phasic and tonic contractions of the portal vein.
Sodium nitroprusside depolarized the membrane of the was deferens but did not alter the depolarization by K-Tyrode's solution. Potentiation of the phasic contraction was also observed following the pretreatment with 20mM K⁺.
When sodium nitroprusside was applied during the course of the tonic contraction, marked relaxation was observed in the portal vein, while only slight relaxation was induced in the was deferens even by high concentrations of the drug. Residual tension in the presence of sodium nitroprusside was completely abolished by the application of verapamil of the concentration higher than 10^-6M. Relaxations of preparation by sodium nitroprusside were counteracted by increases in Ca concentration. When sodium nitroprusside was applied in the presence of moderately elevated-K⁺ (15 to 30mM), an icrease in tension was observed in the was deferens and a decrease in tension Sodium nitroprusside on potassium contracture was observed in the portal vein.
The differences in the action of sodium nitroprusside on the was deferens and on the portal vein may be explained by the differences in the action of the drug on cell membrane, especially on the membrane potential.

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Two types of experiments were performed in dogs to clarify physiological state during vesico-ureteral reflux (VUR). In the first experiment, VUR was established by performing operations to disturb the VUR protecting mechanism. In the second experiment, a tube was inserted into the uretero-vesical junction to prepare VUR model and using this model VUR was induced experimentally. In these experiments, recordings of ureteral myogram, intravesical pressure and intrapelvic pressure as well as macroscopic observations of the ureter were made and the following results were obtained.
1) Functional failure of the ureteral orifice was the most important factor for the development of VUR.
2) When the ureteral orifice showed functional failure, VUR appeared at a mean intravesical pressure of 20cmH₂O.
3) During VUR developed, ureteral peristalsis occurred frequently, whereas no ureteral contraction was observed macroscopically.
4) Antiperistalsis was not an immediate factor responsible for the induction of VUR.
5) In the presence of VUR, intrapelvic pressure became lower than intravesical pressure.
These findings seemed to have properly reflected the physiological states in patient with VUR.

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Electrical field stimulation (EFS), transmural nerve stimulation, was utilized to investigate autonomic nerve innervation of cat pulmonary artery. EFS (duration; 0.8 msec or 1.0 msec, frequency; 20 Hz, voltage; 70 V, for 15 sec) induced small fast constriction followed by large prolonged relaxation on prostaglandin H2 analog-precontracted cat pulmonary arterial strip which was suspended in a 10ml organ bath. The small fast constriction was blocked or considerably reduced by addition of phenoxybenzamine. The relaxation was partially blocked in some strips by addition of atropine and/or propranolol. Teterodotoxin or lidocaine not only blocked relaxation which was not blocked by atropine or propranolol, but also farther reduced or completely blocked the relaxation which was partially blocked by atropine and/or propranolol. It is concluded that (1) α-adrenergic nerve regulates pulmonary arterial constriction, (2) β-adrenergic and cholinergic regulations may be present, but their roles may be substantially small and (3) non adrenergic non cholinergic nerve may play major roles in inhibitory regulation of cat pulmonary circulation.

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Influeces of pH change in the medium on actions of papaverine were investigated in the intestinal smooth muscle of guinea pigs and compared with those of verapamil, a Ca²⁺ entry blocker. Papaverine contracted the ileal longitudinal muscle and inhibited the CaCl₂ -induced contraction of depolarized taenia coli. When the external pH was varied stepwise within the range of 6.8 to 7.6, both actions were equally facilitated with a lowering of the pH. A good correlation between these facilitated responses and the amount of ionized papaverine molecules was observed. Meanwhile, verapamil also induced the smooth muscle contraction and the inhibition of CaCl₂-induced contraction. Although the dual action of verapamil were facilitated with a drop in the pH, the magnitudes of these facilitation were less than those of papaverine. Moreover, verapamil was less effective in inducing the smooth muscle contraction, but more potent in inhibiting the CaCl₂ -induced contraction, as compared to papaverine. These results indicate the possibility that ionized papaverine may displace bound calcium on the cell membrane of smooth muscle and this displacement may result in transient inward movement of Ca²⁺, leading to contraction and that subsequent blockade of Ca²⁺ entry by papaverine may block the contraction. These results also suggest that papaverine and verapamil may cause the dual action through a different mechanism.

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In the present study, the effects of prostaglandin I₂ (PGI₂) on the vasoconstrictor response to adrenergic nerve relating agents was examined using the perfused arterial preparations, i.e., the isolated perfused central artery of a rabbit ear and its perfused arterial segment. The following results were obtained.
1. PGI₂, 3.0 to 9.0ng/m/, slightly enhanced not only the vasoconstrictor response to electrical stimulation of the perivascular sympathetic nerve (VSNS), and that to the exogenously applied noradrenaline, but also the noradrenaline-induced contracture.
2. In the experiment examining the effect of VSNS on 6-keto-PGF_1α, a main metabolite of PGI₂, levels in the effluent perfusate, it was clarified that 6-keto-PGF_1α levels following VSNS were lower than those before VSNS.
These results seem to suggest that PGI₂ is a weak vasoconstrictor in a rabbit ear and the endothelium of vascular wall would be inclined to be damaged by the mobilization of an adrenergic nerve transmitter.

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