The electrical activities of three peri-anal muscles; internal anal sphincters, external anal sphincters and anal longitudinal muscles in decerebrate dogs and cats, were recorded by single, bipolar, macro-electrodes with identical methods, as those described by Ihara & Takahira (1984) and by Tamura & Takahira (1985). The overwhelming activity could vary in different experiments, however, the activity of internal sphincters-slow spikes, was mostly revealing in majority of experiments.
The waxing and waning amplitudes of internal sphincter-slow spikes were seen in almost all records, but their waxing cycles were not synchronized between different recording foci in single animals. Further, such alteration of spike size did not directly correlate with detectable change of anal canal pressure. Rather, the waxing and waning of slow spikes seem to be due to a ‘beating’ of pacemaker waves, originated from multiple generators in internal sphincters. Intravenous injection of ‘somatic’ neuro-muscular blocking agent; suxamethonium chloride, did not cause any alteration of pressure level and of internal sphincter-slow spike rate, indicating that the anal canal pressure was primarily dependent on sustained activity of internal sphincters, not on tonic discharge of external sphincters.
The graded increase of distension volume in rectum brought about progressive lengthening of inhibition of internal sphincters, in turn, causing prolongation of falling phase of pressure in the recto-anal reflex. Although the tonic discharge of external sphincters in decerebrate animals was also completely inhibited by rectal distension, this silence did not induce any significant change in anal canal pressure. It is concluded that the external sphincter is not a tonic pressure-yielding element except a transient squeeze of anal canal, instead, it is a resistive element against complete relaxation of tonic pressure-yielding internal sphincter.

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Cisapride is a novel gastrointestinal prokinetic drug.
The aim of the present study was to investigate gastric emptying time and secretion of gastrointestinal hormones (Gastrin, Motilin, Glucagon) after single oral intake of 5 mg or 10 mg cisapride. The healthy men aged 23-55 years participated the study. The gastric emptying time and gastrointestinal hormones were measured by γ-camera radioisotopic technique and radioimmunoassay, respectively. The half time of emptying phase was reduced from 31.78 min to 29.88 min, and emptying rate increased in 10 mg cisapride group.There was a tendency that cisapride accelerated a stimulation of Motilin secretion.

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The inner circular muscle (ICM) of the cat duodenum at the choledocho-duodenal junction is thickened, surrounding the choledochus at its proximal portion within the duodenal wall. Such a thickened portion of ICM is considered to be a main partwhich serves as a sphincter of the choledochus. This portion of the ICM was referred to as ‘sphinter of choledochus’ in the present study. The sphincter of choledochus and the adjacent ICM were studied by freeze-fracture and conventional thin sectioning methods by electron microscopy in order to clarify themorphological characteristics of smooth muscle cells in the sphincter of choledochus in comparison with ICM.
Smooth muscle cells of the sphincter of choledochus were smaller (3-5μm in diameter) in size, and had less developed dense patches and dense bands. However, they were richly innervated and had numerous gap junctions for electric coupling between cells. These findings indicate that sphincter of choledochus, though its contraction ability may be weaker than the ICM, can exhibit a highly synchronized contraction needed for the sphincter function.

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Masayuki Hasegawa, Mamoru Kobayashi, Hideto Oyamada, Tomoko Kamishima, Chieko Yoshida, Hisayuki Ohata, Ikuo Maruyama, Kazutaka Momose and Yasuo Gomi. Studies on isolated smooth muscle cells. IX. Application of papain for isolation of single smooth muscle cells from guinea pig taenia coli. Jpn. J. Smooth Muscle Res. 1987, 23 (1), 35-46.-To prepare single smooth muscle cells from the taenia coli of guinea pig, the application of papain to the enzymatic solution was examined under two conditions: 1) the isolation in a modified Tyrode solution (containing 0.18 mM Ca²⁺: 0.18mM Ca²⁺-Tyrode solution) and 2) the isolation in a high-K⁺ Tyrode solution (Na+ was replaced by K⁺, and Ca²⁺ was not added: high-K⁺ Tyrode solution). The presence of papain during collagenase digestion reduced contamination of broken cells and cell debris. In the case of the high-K⁺ Tyrode solution, papain increased the yield of single cells significantly. The cells were contracted in a dose-dependent manner by Ca²⁺ in the high-K⁺ Tyrode solution and by carbachol in 0.18 mM Ca²⁺-Tyrode solution; furthermore, the contractions were antagonized by verapamil and atropine, respectively. Treatment with papain did not affect cell sensitivity to the stimulants. Therefore, our results suggest that the addition of papain is useful for the isolation of single cells to investigate the physiological and pharmacological characteristics of smooth muscle.

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Shimizu, K., Hori, M., Mitsui, M., Hayashi, Y., Nakajyo, S. and Urakawa, N. The properties of a high K⁺-induced contraction in the ileal longitudinal and circular muscles of cat. Japanese Journal of Smooth Muscle Research 1987, 23 (1), 47-53. Hypertonic 60 mM KC1 (H 60K⁺) solution induced a phasic contraction followed by tonic one in the longitudinal (long.) and circular (circ.) muscles of cat ileum. Verapamil inhibited the tonic contraction in the long. or circ. muscle with IC₅₀ of 2.0×10^-8 M or 1.0×10^-7 M, respectively. The sensitivity of the long. muscle to verapamil was higher than that of the circ. muscle. Ouabain (10^-5 M) increased or did not change the tonic contraction, and increased intracellular Na+ contents in the long. and circ. muscles in H 60K+ solution. Li⁺-substituted (1/5-1/2) solutions decreased the H 60K⁺-induced contraction in the long. muscle, but potentiated or did not change the contraction in the circ. one. The results with glucose removal, hypoxia, DNP application and a measurement of oxygen consumption showed that the H 60K⁺-induced contractions in the long. and circ. muscles are probably dependent on aerobic metabolism utilizing external glucose as well as endogenous substrates. In summary, properties of the H 60K⁺-induced contraction in the ileal long. of cat was not entirely similar to those of circ. muscles, but they were different from those of the ileal of other animal species and had some similarities to those of the guinea-pig portal vein.

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