Spontaneous Bladder Contractions Research Articles

Motility of the urinary bladder in cats during filling at physiological rates. III. Spontaneous rhythmic bladder contractions in the conscious and anesthetized animal. Influence of distension and innervation.

Spontaneous rhythmic bladder contractions were studied in conscious and anesthetized cats. Rhythmic activity was absent in the awake state, but appeared during deep relaxation or sleep. Usually, marked rhythmic bladder activity was present in the anesthetized cat, showing a differentiated reaction to distension. In response to physiological filling rates and various bladder volumes the spontaneous rhythmic contractions of the intact bladder had a frequency of 1-4/min, amplitudes up to 20 cm H2O (majority between 5-15 cm H2O) and a duration of 10-20 sec. The smallest increase in the rate of filling necessary to cause a rise in frequency was 0.08 ml/min (~1.5 hour-diuresis). When the entire collecting phase was recorded during a gradual rise in filling rate, a typical pattern often occurred. The first response of the rhythmic contractions was a rise in amplitude followed by increased frequency. Towards the micturition the amplitude decreased while the frequency continued to increase. The volume threshold of...

Evoked responses in the anterior brain stem of cats during urinary bladder contractions

Neural activity in various regions of the anterior brain stem were studied during spontaneous bladder contractions using evoked potential techniques in awake, immobilized cats. Potentials were evoked in diencephalic and mesencephalic regions by stimulation of the sciatic nerve. Each potential was classified into one of five categories depending on the bladder pressure. Compared to control, some potentials in other categories were either enhanced or suppressed during the contraction or, in some cases, a combination of both occurred. The latter triphasic responses consisted of either an increase or a decrease during the pre- and postcontraction periods with the opposite effect during the contraction. Responses were particularly evident in red nucleus, superior colliculus, substantia nigra, central gray, and mesencephalic reticular formation. These results were interpreted with respect to previous studies which associate these structures with bladder function and in terms of brain stem integration of multiple sensory inputs.

Mechanosensitive afferent units in the hypogastric nerve of the cat.

1. Recordings have been made from ninety single afferent units in the hypogastric and lumbar splanchnic nerves of the cat. 2. The majority of units examined had properties similar to those previously described in the splanchnic nerve: they were slowly adapting mechanoreceptors with one to six punctate mechanosensitive sites distributed mainly along blood vessels as they approached the viscera in peritoneal ligaments; they had a wide range of mechanical thresholds and conduction velocities in the range 0.5-24 m s-1. 3. Receptive fields were found over the bladder base or its peritoneal ligaments or both, on the uterus or broad ligament or both, on the colon or mesocolon or both, and in association with the ureter, vas deferens, prostate or pelvic fat pads. 4. Discharges from afferent units associated with the bladder were investigated during spontaneous (or reflex) bladder contractions, passive distensions, and tetanic contractions induced by electrical stimulation of the sacral spinal cord. The mean spike rates of the adapted (tonic) discharges, observed during distensions and induced tetani, differed over part of the range of intravesical pressures examined. Their behaviour is discussed in relation to the concept of 'in series' tension receptors within the bladder wall.

Mechanisms underlying recurrent inhibition in the sacral parasympathetic outflow to the urinary bladder.

1. In cats with the sacral dorsal roots cut on one side electrical stimulation (15-40 c/s) of the central end of the transected ipsilateral pelvic nerve depressed spontaneous bladder contractions. The depression was abolished by transecting the ipsilateral sacral ventral roots. 2. Electrical stimulation of acutely or chronically transected ('deafferented') sacral ventral roots depressed spontaneous bladder contractions and the firing of sacral parasympathetic preganglionic neurones innervating the bladder. The depression of neuronal firing occurred ipsilateral and contralateral to the point of stimulation, but only occurred with stimulation of sacral roots containing preganglionic axons and only with stimulation of sacral roots containing preganglionic axons and only at intensities of stimulation (0-7-4V) above the threshold for activation of these axons. 3. The inhibitory responses were not abolished by strychnine administered by micro-electrophoresis to preganglionic neurones, but were blocked by the intravenous administration of strychnine. 4. The firing of preganglionic neurones elicited by micro-electrophoretic administration of an excitant amino acid (DL-homocysteic acid) was not depressed by stimulation of the ventral roots. 5. It is concluded that the inhibition of the sacral outflow to the bladder by stimulation of sacral ventral roots is related to antidromic activation of vesical preganglionic axons. Collaterals of these axons must excite inhibitory interneurones which in turn depress transmission at a site on the micturition reflex pathway prior to the preganglionic neurones.

Imipramine and Enuresis

To the Editor.— Great speculation concerning imipramine's mechanism of action in enuresis continues. Some describe augmentation of internal urethral sphincter tone as the primary effect.1Studies of micturition and sleep patterns during continuous monitoring2of intravesical pressure describe the following: Increase in bladder pressure during sleep stages III and IV. Increase in uninhibited spontaneous bladder contractions in sleep stages III and IV. Decrease in contractions and low intravesical pressure in REM sleep and in NREM sleep stages I and II. A unifying hypothesis suggests a fundamental defect in enuretic children in subcortical centers controlling micturition, in maturation of neural pathways, and in the level of sleep. Initiation of the enuretic episode from stage IV sleep suggests the loss of voluntary control over micturition, possibly due to generalized cortical depression.3The greater frequency of spontaneous bladder contractions in both infants and enuretic children suggests a

Reflex effects of slow bladder filling on the blood pressure in cats.

The effect of slow bladder distension on mean arterial blood pressure has been studied in the cat anawsthetized with chloralose. In fifteen cats out of eighteen, slow bladder filling was associated with a steady rise in blood pressure of not more than 30 mm.Hg.; this rise was slowly adapting or compensated, and was unaffected by baroreceptor denervation. In eleven out of fourteen cats, spontaneous isometric bladder contractions were associated with a rise in blood pressure of more than 20 mm. Hg which was rapidly compensated, and was accentuated after baroreceptor denervation. In fifteen cats out of eighteen, bladder emptying was associated with a fall in blood pressure, the blood pressure returning to the basal level after an initial overshoot. No changes in blood pressure were observed in response to direct pressure on the bladder or to bladder ischæmia. Three cats out of a total of twenty‐nine showed depressor or biphasic blood pressure responses to slow bladder filling and to spontaneous isometric bladder contractions. Possible afferent receptors for these bladder viscero‐vascular reflexes are discussed; and consideration is given to the rôle of the cardiovascular stabilizing reflexes in partially compensating the spinal viscerovascular reflexes in the intact animal.