Slow potential variations of small intestine

SUMMARYThe membrane properties of single cells of intestinal smooth muscle of duodenum, jejunum, ileum, caecum and rectum of guinea-pig have been studied.1. The membrane potentials of longitudinal muscles of the duodenum, jejunum, ileum, caecum and rectum varied from 54 to 56 mV and those of circular muscles of jejunum, ileum, caecum and rectum varied from 57 to 60 mV. The ablated longitudinal muscle had a slightly lower value (50 mV) than the intact one.2. The longitudinal muscle generated spontaneous discharges but these were rare in the circular muscles of the intestine except for the caecum. Overshoot potentials could be observed in all regions of the intestine. The maximum rate of rise of the spontaneously discharging longitudinal muscles varied from 11 to 18 V/sec.3. Not all of the slow potential changes (but at least some) were generated by the nervous elements distributed between the muscle layers and in them.4. The conduction velocities measured from the longitudinal muscles of jejunum and rectum in the presence of tetrodotoxin were 2*1 cm/sec and 4 0 cm/sec respectively. 5. Chronaxies of the longitudinal muscles of jejunum and rectum were 2-5 msec and 5-18 msec respectively.6. Intracellular stimulation of the single cells of the duodenum and caecum could trigger a spike, similar to that observed in the taenia coli. The spikes were mostly graded ones; a spike of full size was rarely elicited. When the spikes were triggered, the after-hyperpolarization appeared consistently presumably caused by the increased potassium conductance.7. The effective membrane resistance and the time constant were measured for the longitudinal muscles of the jejunum and rectum. When spikes were generated by intracellular stimulation the observed values were H. KURIYAMA, T. OSA AND N. TOIDA 40-50 MQ and 3-5 msec in both tissues. These values were the same as those observed in the taenia coli.8. When the time constant of the membrane was measured by the extracellular polarizing method, the longitudinal muscles of the jejunum especially and the rectum had smaller time constants than the taenia coli.9. The differences of conduction velocity and chronaxie of the different regions of the intestine are discussed in relation to the cable properties of the tissues which are directly influenced by the morphological arrangements of the tissues.

Section: Resultsmentioning

confidence: 94%

Electrophysiological study of the intestinal smooth muscle of the guinea‐pig

Kuriyama¹,

Osa²,

Toida³

1967

“…Barium prolongs the slow depolarization of the membrane in cat intestinal muscle (Bortoff, 1961), and prolongs the negative after-potential in rat and guinea-pig ureter (Bennett, Burnstock, Holman & Walker, 1962). In the taenia coli, barium depolarized the membrane and delayed the repolarization of the spike.…”

Section: Discussionmentioning

confidence: 99%

Effects of changes in the external sodium and calcium concentrations on spontaneous electrical activity in smooth muscle of guinea‐pig taenia coli

Bülbring¹,

Kuriyama²

1963

228

“…When the interval of the stimulation was shorter, the stimulation elicited the small depolarization directly, then the spike was generated (c-f). Effects of Ba2+ and tetrodotoxin on the membrane activity Ba2+ ion is known to increase frequenev and duration of the spike of the smooth muscle cell (Burmstock & Prosser, 1960;Bortoff, 1961;Biilbring & Kuriyama, 1963). In the ureter, 10-5 M-Ba2+ generated spike discharges like those of a spontaneously active cell.…”

Section: Membrane Potential and Spice Di8chargesmentioning

confidence: 99%

Membrane properties of the smooth muscle of guinea‐pig ureter

Kuriyama¹,

Osa²,

Toida³

1967

SUMMARY1. The membrane properties of the guinea-pig ureter were studied in physiological Krebs solution by intra-and extracellular stimulating methods.2. The mean membrane potential was 50 mV. Action potentials triggered by external stimulation were composed of repetitive spikes and a plateau phase.3. The effects of intracellular polarization on the membrane activity elicited by extracellular stimulation were observed. Anodal polarization enhanced the amplitude and the maximum rate of rise of the spike while cathodal polarization reduced them. The number of the spikes, the duration and amplitude of the plateau phase were not changed by polarization of any direction.4. The spikes triggered by intracellular stimulation were mostly graded, but repetitive spikes sometimes continued even after cessation of the stimulation. The effective membrane resistance was 15-23 MQ and the time constant was 2-3 msec.5. Conduction velocity (V), chronaxie, time constant (T) and space constant (A) of the tissue were measured by extracellular stimulation. These values were as follows: V, 3-6 cm/sec; chronaxie, 20-40 msec; r, 200-300 msec; A, 2-5-3 mm. The conduction of excitation might be related to the cable properties of the tissue.6. The relative refractory period measured by extracellular stimulation was as long as 30 sec. During the relative refractory period dissociation of the slow depolarization and the spikes was observed by successive stimuli.7. The plateau phase was prolonged and the frequency of the spontaneous discharges was increased by treatment with Ba2+. Tetrodotoxin had no effect on spike activity nor on the plateau phase, but Mn2+ blocked the membrane activity. Physiol. I9II5