Effects of rapid cooling on the electrical properties of the smooth muscle of the guinea-pig urinary bladder

Influence of urodynamic conditions on bladder sensations and detrusor activity in patients with multiple sclerosis

AIMS

The study aimed to assess the impact of bladder filling rate and fluid temperature during urodynamics on bladder sensations and volume of apparition of detrusor overactivity in patients with multiple sclerosis (PwMS).

METHODS

Consecutive PwMS assessed with a standardized urodynamic test including three consecutive cystometries (20 ml/min, 100 ml/min, and 100 ml/min with 4°C fluid (Ice water test [IWT]) between June 2020 and March 2022 were included in this retrospective study. Data collected were bladder sensation with first desire to void (FDV) and strong desire to void (SDV). The presence of detrusor overactivity (DO) and the volume of the first uninhibited detrusor contraction were recorded.

RESULTS

One hundred and fifty-seven patients (mean age 47.4 ± 11.8 years, median EDSS 3 IQR[2-5], 73.9% of women) were included. Increased filling rate induced delayed bladder sensations (FDV 219 ± 109 ml vs. 194 ± 100 ml; SDV 349 ± 113 ml vs. 322 ± 124 ml for 100 ml/min and 20 ml/min filling rate, respectively, p < 0.001). Ice water increased bladder sensations with earlier reports of needs to void (FDV 163 ± 99 ml vs. 218 ± 117 ml; SDV 263 ± 104 ml vs. 351 ± 112 ml respectively; p < 0.001). Thirty-four patients had DO during both 20 ml/min and 100 ml/min fillings, without difference in the volume of apparition (p = 0.78). Forty-four patients had DO during both 100 ml/min and IWT. Detrusor overactivity appeared for a reduced volume during IWT compared with room temperature fluid perfusion (-68 ml [-95 to -41]; p < 0.001).

CONCLUSION

Filling rate and fluid temperature impact bladder sensations during cystometry in PwMS. Ice water decreased the volume of the first uninhibited detrusor contraction.

Role of Ca(2+) in the rapid cooling-induced Ca(2+) release from sarcoplasmic reticulum in ferret cardiac muscles

Rapid lowering of the solution temperature (rapid cooling, RC) from 24 to 3°C within 3 s releases considerable amounts of Ca²⁺ from the sarcoplasmic reticulum (SR) in mammalian cardiac muscles. In this study, we investigated the intracellular mechanism of RC-induced Ca²⁺ release, especially the role of Ca²⁺, in ferret ventricular muscle. Saponin-treated skinned trabeculae were placed in a glass capillary, and the amount of Ca²⁺ released from the SR by RC and caffeine (50 mM) was measured with fluo-3. It was estimated that in the presence of ATP about 45% of the Ca²⁺ content in the SR was released by RC. The amount of SR Ca²⁺ released by RC was unchanged by the replacement of ATP by AMP-PCP (a non-hydrolysable ATP analogue and agonist for the ryanodine receptor but not for the Ca²⁺ pump of SR), suggesting that the suppression of the Ca²⁺ pump of SR at low temperature might not be a major mechanism in RC-induced Ca²⁺ release. The free Ca²⁺ concentration of the solution used for triggering RC-induced Ca²⁺ release was estimated to be only about 20 nM with fluo-3 or aequorin. When this solution was applied to the preparation at 3°C, only a small amount of Ca²⁺ was released from SR presumably by the Ca²⁺-induced Ca²⁺ release (CICR) mechanism. Thus, in mammalian cardiac muscles, RC releases a part of the (<50%) stored Ca²⁺ contained in the SR, and the mechanism of RC-induced Ca²⁺ release may differ from that of CICR, which is thought to play a role in frog skeletal muscle fibres that express ryanodine receptors of different types.

Influence of temperature on activity of the isolated whole bladder preparation of neonatal and adult rats

The temperature sensitivity of in vitro whole bladder preparations from neonatal and adult rats with or without chronic partial urethral obstruction was investigated. After the bladder was filled to a volume eliciting isovolumetric contractions, temperature was changed between 19 and 38 degrees C. In all preparations, higher temperatures were associated with higher frequencies of spontaneous intravesical pressure waves (IVPW). In 1- to 2-wk-old neonates, IVPW amplitude increased as the temperature increased; however, in older neonates and normal adults, the opposite occurred. The transition period was at 3 wk of age when bladder volume also markedly increased. At this age as well as in adult rats with outlet obstruction, changing temperature had little influence on the amplitude of IVPW. Thus obstructed outlet bladders and 3-wk-old bladders had similar properties. It is concluded that the properties of bladder muscle are changed during postnatal maturation and that in 3-wk-old rats, when brain control of voiding is emerging, micturition is abnormal, leading to obstructive changes in bladder muscle.

The ice-water test--a simple and valuable supplement to routine cystometry

The results of cystometrograms and ice-water tests (IWTs) were retrospectively evaluated in 557 patients with overactive bladders, lower motor neuron lesions or pure stress incontinence. The IWT was considered positive when, following ice-water instillation, the fluid was expelled from the bladder within 1 min. The test was considered false negative when no fluid escaped despite a sustained detrusor contraction of the same magnitude as the micturition contraction. Ninety-seven percent of patients with complete and 91% of those with incomplete upper motor neuron lesions had a positive or a false negative IWT. About 75% of the patients with multiple sclerosis, Parkinson's disease or previous cerebrovascular accident had a positive IWT. All patients with lower motor neuron lesions or pure stress incontinence had a negative IWT. There was a significant correlation between a positive IWT and an abnormal sensation of bladder filling and inability to inhibit micturition voluntarily, as well as between a negative IWT and the occurrence of phasic detrusor contractions during cystometry. The study shows that the IWT is a sensitive test for differentiating upper from lower motor neuron lesions. It is also a useful parameter for functional subdivision of overactive bladders. In patients with voiding dysfunction in the absence of lower urinary tract inflammation, a positive test is an indicator of a silent or overt neurological disorder.

A bladder-to-bladder cooling reflex in the cat

1. Reflex effects of cold stimulation of the lower urinary tract were studied in cats anaesthetized with alpha-chloralose. The bladder and the urethra were catheterized for separate fluid instillations and the bladder pressure was monitored together with the evoked efferent nerve responses in pelvic nerve filaments. 2. A bladder cooling reflex could be evoked from both the bladder and the urethra. The response was an efferent discharge in preganglionic pelvic motor fibres to the bladder. 3. Bladder mechanoreceptors that drive the normal micturition reflex were not directly involved in the cooling reflex. Their tension sensitivity was decreased by cooling and the efferent reflex response typically occurred before any activation of these receptors. The efferent activity of the cooling reflex also survived an intentional unloading of the mechanoreceptors, a manipulation that abolishes the normal micturition reflex. 4. The dynamic threshold temperature of the cooling reflex was about 30-32 degrees C, which was at the thermal neutral point of the bladder in our experimental situation. 5. The bladder-evoked component of the reflex was greatly reduced or abolished by an intravesical infusion of the local anaesthetic Xylocaine. It was also abolished by total bladder denervation. 6. The vesical component of the reflex was unchanged by bilateral transections of the hypogastric nerves but abolished by pelvic nerve transection. The cooling reflex from the distal urethra was abolished by transection of the pudendal nerves. 7. It was proposed that the cooling reflex originates from cold receptors in the bladder and urethral walls and that the responsible afferent fibres are unmyelinated C fibres. The function of the reflex may be to rid the body of a thermal ballast when under cooling stress.

Carbachol contracture of stomach smooth muscle of the newt in calcium-free solution

A small muscle preparation of stomach circular muscle of the newt responded to carbachol (CCh) with a phasic contracture. At 20 degrees C, in Ca-free Ringer solution (+1 mM EGTA), the amplitude of CCh contracture was very rapidly inhibited to less than 10% of that in normal Ringer solution (1.8 mM Ca). The amplitude of this CCh contracture was markedly enhanced with increasing [K]0. CCh contracture in Ca-free Ringer solution was also enhanced after K contracture was induced once in the presence of 1.8 mM Ca, followed by soaking in normal Ringer solution. The amplitude of this enhanced CCh contracture persisted up to about 5 min, following rapid decrease to about 70%, and then gradually decreased to a steady level in Ca-free Ringer solution. This decrease in amplitude was prevented by increasing [K]0 during soaking in Ca-free solution; even when the temperature was elevated from 20 to 35 degrees C during the periods of soaking in Ca-free solution, CCh contracture was inhibited only by about 20% in Ca-free high K solution, whereas in Ca-free or Ca-free low Na (Tris) Ringer solution it was inhibited by more than 50%.

Influence of lowered temperature upon the response of prostatic and epididymal portion of the rat isolated vas deferens to field stimulation

This paper reports the effects of lowering (bath) temperature upon contractile responses of prostatic and epididymal ends of the rat isolated vas deferens to electrical field stimulation. Responses to field stimulation with single pulses at 60 s intervals were potentiated by lowering the bath temperature. This effect was maximal at temperatures of 25-27 degrees C and was reduced in preparations treated with phentolamine (5 mumol/l). Field stimulation with trains of 50 pulses at 5 Hz every 5 min produced biphasic contractions of preparations. The initial, twitch-like component, prominent at the prostatic end and resistant to blockade by phentolamine (5 mumol/l) was little affected by lowering the bath temperature from 37.5 degrees C to 19 degrees C. In contrast, the second, more prolonged, component of the response to pulse trains, which was prominent at the epididymal end of the tissue was decreased by lowering the bath temperature and by phentolamine. In the epididymal segment, responses to exogenous noradrenaline were enhanced by lowering the bath temperature. It is concluded that lowering the bath temperature enhances the contractility of the vas deferens in response to the release of neurotransmitters and to the application of exogenous noradrenaline via a postsynaptic action. In addition, via a presynaptic action, lowering the bath temperature depresses or delays the release of the noradrenergic transmitter from the sympathetic nerve terminals.

Effects of rapid cooling on mechanical and electrical responses in ventricular muscle of guinea-pig

The effect of rapidly lowering bathing solution temperature from 36.5 +/- 0.5 degrees C to various low temperatures was examined in guinea-pig ventricular muscle to explore the possible role of intracellular Ca2+ store sites in excitation-contraction coupling. Rapid cooling from 36.5 +/- 0.5 degrees C to below 18 degrees C caused contracture (rapid cooling contracture, r.c.c.) with subthreshold depolarization for contraction, if electrical stimulation was applied before cooling. R.c.c. peak tension depended on cooling temperature, and pre-cooling stimulation frequency and duration. R.c.c. induced after pre-cooling stimulation was enhanced by increased extracellular Ca2+ ( [Ca2+]o) and decreased by reduction of [Ca2+]o. Co2+ (2-4 mM) added to the HEPES-buffered Krebs solution, which suppressed the action potential plateau and inhibited twitch response, did not abolish r.c.c. after pre-cooling stimulation at high frequency. Reduction of extracellular Na+ concentration ( [Na+]o) before cooling enhanced r.c.c., and even in non-stimulated preparations, incubation in low [Na+]o below 68.8 mM for 20 min produced r.c.c. R.c.c. was superimposed on the tonic component of the K+ contracture, after a quiescent preparation has been depolarized beyond -40 mV by addition of solid KCl to normal Krebs solution. The relation between r.c.c. tension and membrane potential was shifted to the left along the voltage axis by reducing [Na+]o and shifted to the right by decreasing [Ca2+]o. Results suggest that well-developed intracellular Ca2+ store sites could sequester enough Ca2+ to generate tension by an energy-dependent process which had been loaded mainly by a voltage-dependent Na+-Ca2+ exchange mechanism and Ca2+ current, and that rapid cooling could cause Ca2+ release from the intracellular store sites with little contribution to membrane excitation in the guinea-pig ventricular muscle.

Mechanisms of the temperature effect on airway smooth muscle

We studied the effect of sudden cooling and warming on the contractile response of tracheal segments (TS) isolated from guinea pigs. After a standardized incubation period in normal physiological salt solution (PSS) (t degree = 37 +/- 0.5 degree C, pH = 7.34 +/- 0.02, PCO2 = 24 +/- 2 Torr, PO2 = 430 +/- 5 Torr) TS were quickly (20 sec) exposed to cool (24 degrees, 26 degrees, or 29 degrees C) PSS and changes in isometric force were measured using a Grass 0.03 transducer. Following the cooling period, maintained for 10-15 min, tissues were exposed to 34 +/- 0.5 degree C warm PSS and contractile response was measured again. It was found that: (1) quick cooling (24, 26 and 29 degrees C) induced a contraction of TS followed by a slow relaxation. The magnitude of the contraction was a function of temperature; the highest contraction was observed at 24 degrees C; (2) cooling, lower than 22 degrees C induced only a relaxation of TS; (3) quick warming of TS induced a biphasic response, i.e., a small relaxation followed by a slow, large contraction; (4) contraction as induced by cooling and relaxation as induced by warming were dependent on the initial length of the TS; (5) Cooling-induced contraction and warming-induced relaxation were inhibited with ouabain (10(-5) M); (6) Warming-induced contraction was attenuated with aspirin (50 micrograms/ml); but aspirin potentiated (P less than 0.001) cooling-induced contraction; (7) warming-induced contraction was inhibited with FPL 55712 (10(-6) M) (P less than 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

Electrical and mechanical activity of the isolated lower urinary tract of the guinea-pig

1 Strips of urethra taken from guinea-pigs contracted in response to acetylcholine, noradrenaline (via alpha-adrenoceptors) and 5-hydroxytryptamine, and were relaxed by adenosine triphosphate (ATP) if the tone was raised. Isoprenaline produced relaxation of bladder strips (via beta-adrenoceptors) whereas ATP caused contraction. 2 Atropine completely blocked all responses to acetylcholine; quinidine failed to block ATP responses selectively; methysergide blocked responses of the urethra but not the bladder to 5-hydroxytryptamine. 3 Spontaneous electrical activity was recorded with intracellular microelectrodes from all regions: in the urethra infrequent bursts of spikes occurred at 1-7 min intervals; regular spikes at 6-30/min were recorded from the detrusor muscle. In the bladder base, bursts of spikes were superimposed on the regular pattern. 4 Bursts of spikes in the urethra were initiated by noradrenaline, phenylephrine or acetylcholine and inhibited by ATP; regular spikes in the bladder were accelerated by acetylcholine or ATP and slowed by noradrenaline or isoprenaline. 5 The intrinsic electrical activity and pharmacological properties of the urethra therefore differ from those of the bladder. This may account for the different responses of the two regions in normal function.

Adrenergic transmissions in the guinea-pig mesenteric artery and their cholinergic modulations

1. Neuromuscular transmission in the guinea-pig mesenteric artery and the effect of acetylcholine (ACh) on transmission were investigated by the micro-electrode method. 2. The membrane potential, length and time constant of the smooth muscle of the mesenteric artery were found to be -69.6 +/- 1.9 mV, 0.81 +/- 0.15 mm and 129 +/- 42 msec, respectively. 3. Perivascular nerve stimulation produced an excitatory junction potential (e.j.p.) and repetitive stimulation produced facilitation. When the amplitude of an e.j.p. reached threshold, a spike was evoked. 4. Very rarely, miniature e.j.p.s. were recorded. The amplitude histogram showed a skew distribution. Increases in the stimulus intensity enlarged the amplitude of e.j.p.s. as a stepwise manner. These results indicate multiple innervation to the muscle cells. 5. The time constant of the falling phase of an e.j.p. was consistently larger than that of the muscle membrane. 6. ACh, in concentrations of less than 10(-8) M, suppressed the e.j.p. amplitude without change in the membrane potential and resistance of the muscle membrane, but accelerated facilitation. These ACh actions were suppressed by pre-treatment with atropine. 7. ACh suppressed neither the conduction velocity of excitation of adrenergic nerves nor the number of nerves contributing to the generation of an e.j.p. 8. These results suggest that pre- and post-junctional muscarinic receptors possess different sensitivities to ACh, and a low concentration of ACh (less than 10(-8)M solely suppressed the release of noradrenaline by activating the pre-junctional muscarinic receptors.