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E Bülbring

Publications and source records attributed to E Bülbring.

At least 37 records · Page 2Linked to original sources
PubMed1969

The effect of temperature on the membrane conductance of the smooth muscle of the guinea-pig taenia coli.

1. The effect of temperature on the membrane conductance of the smooth muscle of guinea-pig taenia coli was investigated electrophysiologically, using the double sucrose gap method, and by ion-flux determinations.2. In the range between 19 degrees C and 37 degrees C, the membrane conductance increased with rising temperature and decreased with cooling (Mean Q(10) about 2.5).3. When the Cl concentration in the external medium was low (Cl(-) substitution with benzene-sulphonate), the effect of changing the temperature was smaller (Mean Q(10) about 1.5).4. In muscle depolarized by excess K (27 mM) in a solution containing low Cl, cooling repolarized the membrane and markedly increased membrane resistance.5. The slow phases of the (42)K- and (36)Cl-exchange were greatly slowed by cooling which did not change the rate constants of the (24)Na-efflux curve. Thus observations on the rate of exchange of ions agreed with the electrophysiological findings indicating a reduction of K- and Cl-conductance of the cell membrane at low temperature.6. The depolarization produced by lowering the external Ca-concentration was greatest at high temperature (37 degrees C). With cooling the membrane was repolarized and membrane resistance increased.7. The sustained state of depolarization observed when the external Ca was replaced by Ba (2.5 mM) at high temperature (37 degrees C) was terminated by cooling.8. The observations may be interpreted by the hypothesis that Ca, located at two different membrane sites, controls, independently, at the outer layer mainly Na- (and Ba-) permeability and at the inner layer mainly K-permeability, the Ca-binding at these sites being affected by temperature in the opposite direction.

Animals↗
PubMed1969

The effect of sodium and calcium on the action potential of the smooth muscle of the guinea-pig taenia coli.

1. Spontaneous spike activity and action potentials evoked by external field stimulation were recorded, intracellularly and with the double sucrose gap method, from the smooth muscle of guinea-pig taenia coli.2. Replacement of external NaCl with sucrose (leaving 10 mM-Na in the buffer) caused hyperpolarization and stopped spontaneous activity within 10 min. Spikes could, however, be evoked for 2-3 hr. The amplitude, the overshoot and rate of rise of the spike were increased.3. In 10 mM-[Na](o) the intracellular Na concentration was reduced from 35 to 24 mM, shifting the Na-equilibrium potential from +34 to -22 mV.4. Excess Ca (12.5 mM) caused hyperpolarization and increased membrane conductance. The amplitude and the rate of rise of the spike were increased, the threshold was raised and the latency of the spike evoked by threshold stimulation became shorter.5. The effect of reducing the external Ca concentration depended on the Na concentration present, being greater with higher external [Na](o). When the membrane was depolarized and spikes deteriorated in low Ca (0.2-0.5 mM) reduction of Na to 10 mM caused repolarization and recovery of the action potential.6. Mn (0.5-1.0 mM) blocked spontaneous spike discharge after 20 min. Higher concentrations (more than 2.0 mM) were required to block the evoked action potential.7. The results indicate that the smooth muscle spike in taenia is due to Ca-entry and that Na influences spike activity indirectly by competing with Ca in controlling the membrane potential.

Action Potentials↗
PubMed1968

Membrane potential and ion content in cat and guinea-pig myometrium and the response to adrenaline and noradrenaline.

1. Cats, virgin and 17 days pregnant, and guinea-pigs, virgin and 14-60 days pregnant, or treated for 1-8 days with oestradiol+progesterone, were used. The response of the uterus to adrenaline and noradrenaline was observed and, in pieces from the same tissues, the resting and active membrane potentials were recorded and the ionic content was determined.2. Adrenaline and noradrenaline relaxed the virgin cat uterus, adrenaline being 20-100 times more potent in vivo and about 10 times or less in vitro.3. Adrenaline and noradrenaline caused contraction of the early pregnant cat uterus, the ratio of potency being about 1.4. Adrenaline and noradrenaline had a biphasic effect on the guinea-pig uterus in all conditions. The ratio of potency was about 1.5. The mean membrane potential was 48 mV in virgin cat uterus and 64 mV on the seventeenth day of pregnancy.6. In guinea-pigs the average membrane potential increased from 38 mV in the virgin uterus to 58 mV on the thirtieth day of pregnancy. A similar increase was produced by eight daily injections of 5 mug oestradiol and, on the last 4 days, additional 1.5 mg progesterone.7. In the cat, no significant change in K and Na content was observed during pregnancy. The intracellular chloride content, however, rose from 51.5 m-moles/1. fibre water in the virgin uterus to 89 m-moles in the early pregnant uterus. As a result, the calculated chloride equilibrium potential changed from - 25 mV in virgin uterus to - 11 mV in pregnant uterus.8. In the guinea-pig no significant change in ion content was observed and the calculated potassium and chloride equilibrium potentials remained both unaltered during pregnancy.9. In contrast to guinea-pig uterus in all conditions, and to virgin cat uterus, early pregnant cat uterus was not spontaneously active and excess calcium caused no hyperpolarization.10. The reversal of the uterine response to adrenaline as a result of pregnancy is discussed in relation to the increase of the intracellular chloride content which was only observed in the cat.

Action Potentials↗
PubMed1967

Properties of the inhibitory potential of smooth muscle as observed in the response to field stimulation of the guinea-pig taenia coli.

1. The inhibitory potential evoked by field stimulation of the guineapig taenia coli was studied in hypertonic solution in which the spontaneous electrical and mechanical activity was slowed or abolished.2. There was no direct correlation between the inhibitory potential and the muscle membrane polarization in response to the stimulating current. The chronaxie for the inhibitory potential was less than 1 msec and that for the muscle spike 20-30 msec.3. The inhibitory potential decreased in size along the tissue when one end of the tissue was stimulated, but its spatial decay was slower than that of the electrotonic potential in the muscle bundle.4. Tetrodotoxin (5 x 10(-7) g/ml.) abolished the inhibitory potential without affecting the electrical properties of the muscle membrane. It was concluded that the inhibitory potential was the result of stimulation of intrinsic inhibitory nerves.5. The following properties of the intrinsic nerve fibres were deduced from the experimental results: The length of the nerve fibres is probably only a few mm and the space constant of the order of 0.1 mm. No repetitive firing is produced by a long current pulse. The absolute refractory period is 3-4 msec.

Animals↗
PubMed1967

5-hydroxytryptamine participation in the vagal inhibitory innervation of the stomach.

1. Intraluminal pressure was recorded from the isolated guinea-pig and mouse stomach with the vagus and sympathetic nerves attached.2. The response to vagal stimulation, which consists of an excitatory and an inhibitory component, resembled the response to 5-hydroxytryptamine (5-HT), which has no direct action on the muscle but acts on intrinsic excitatory and inhibitory ganglia.3. In the presence of hyoscine, the effect of vagal stimulation, of nicotinic compounds and of 5-HT were all purely relaxant. Competitive block of ganglionic receptors for acetylcholine reduced the vagal relaxation without antagonizing 5-HT. Specific desensitization of ganglionic receptors for 5-HT reduced the vagal relaxation without antagonizing nicotinic compounds.4. During the early phase of the blocking action of nicotine, responses to vagal stimulation and to 5-HT were both abolished. As the non-specific antagonism changed to the later phase of specific antagonism to acetylcholine, the inhibitory (but not the excitatory) component of the vagal response recovered partially, in parallel with the recovery of the relaxant effect of 5-HT.5. The vagal inhibitory effect was completely abolished only when competitive block of acetylcholine receptors was combined with desensitization of 5-HT receptors.6. Stimulation of the mouse stomach (after asphyxiation of the mucosa and exclusion of the luminal content) in the presence of hyoscine caused the release of 5-HT; this release was blocked by tetrodotoxin.7. The results, together with previous observations that 5-HT is contained within preganglionic nerve fibres in the myenteric plexus, are consistent with the hypothesis that 5-HT, with acetylcholine, may be a neurotransmitter in the vagal inhibitory innervation of the stomach.

Acetylcholine↗
PubMed1967

The effect of adrenaline on the adenosine otriphosphate and creatine phosphate content of intestinal smooth muscle.

1. The smooth muscle of guinea-pig taenia coli was used to investigate the relation between metabolic and physiological effects of adrenaline. Electrical and mechanical activity was recorded with the sucrose gap technique and, in parallel experiments, the concentration of energy-rich phosphate compounds, adenosinetriphosphate and creatine phosphate, (ATP and CP) in the tissue was determined.2. Adrenaline (in concentrations from 2 x 10(-9) g/ml. to 5 x 10(-8) g/ml.) increased the tissue content of energy-rich phosphate compounds. This effect was coincident with the physiological, inhibitory effect on electrical and mechanical activity.3. After anaerobic exposure of the tissue to substrate-free medium, the biochemical and the physiological effects of adrenaline were both abolished; both recovered after readmission of oxygen and/or substrate.4. In muscles depleted of glycogen in substrate-free medium, either by anoxia or by high temperature, adrenaline produced its stabilizing effect on the cell membrane and the increase in ATP and CP content when beta-hydroxybutyrate was the substrate, i.e. in the complete absence of carbohydrate from the medium and from the tissue.5. When adrenaline was applied simultaneously with the readmission of substrate, the ATP and CP content of pieces treated with adrenaline was greater than of control pieces, though the tension of both was zero. This indicates that the effect was not secondary to the muscle relaxation but was the result of increased ATP synthesis.6. The physiological and biochemical effects of adrenaline were both abolished by the same concentration of imidazole (0.05 M).7. Low concentrations of ATP (1 x 10(6)-5 x 10(-6)M)-like adrenaline-inhibited electrical and mechanical activity of the taenia. This effect was also abolished by imidazole.

Journal Article↗
PubMed1967

Oxygen consumption by the isolated smooth muscle of guinea-pig taenia coli.

1. An apparatus is described for simultaneous measurement of oxygen consumption and electrical and mechanical activity of isolated smooth muscle preparations.2. The mean oxygen uptake by the isolated taenia coli of the guinea-pig was 10-20 mul./g/min.3. In spontaneously active preparations, adrenaline (10(-8)-10(-7) g/ml.) caused, with the inhibition of electrical and mechanical activity, a reduction in oxygen uptake.4. After prolonged exposure to substrate free solution spontaneous activity ceased periodically. Adrenaline, when applied during a silent period, had no detectable effect on resting oxygen consumption, while readmission of substrate, either glucose or beta-hydroxybutyrate, increased oxygen uptake.5. Adrenaline did not modify the increased oxygen uptake during the initial recovery period when it was given simultaneously with the substrate. However, adrenaline shortened the time interval which elapsed from the addition of substrate until spontaneous activity was resumed, indicating an acceleration of the recovery process.

Journal Article↗