The reactions of the urinary bladder of the cat under conditions of constant pressure

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Abstract
The urinary bladder exhibits a regular spontaneous rhythmic variation of vol. when the hydrostatic pressure is kept constant. The frequency of the rhythm is increased, and its amplitude diminished, by raising the pressure maintained in the bladder. The effect is reversible. At any given hydrostatic pressure, the bladder assumes a fixed vol. Any attempt to alter its volume also modifies the intravesical pressure. The rhythm may be abolished by deep ether anaesthesia. Contraction and relaxation of the isotonic bladder follow stimulation of the hypo-gastric nerves. Stimulation of the nervi ergentes produces contraction. Section of the hypogastric nerves often increases the amplitude of the rhythm, but never disturbs its regularity. In acute expts., section of the nervi ergentes destroys the regularity of the rhythm. Adrenaline in small doses produces contraction; in moderate doses, relaxation followed by contraction; and in large doses, relaxation alone. The response to adrenaline is not influenced to any extent by the intravesical pressure. Acetylcholine produces contraction or contraction followed by relaxation, the latter especially if the dose be large. The response to acetylcholine is modified by the intravesical pressure. Relaxation is best shown when the pressure is high. Atropine and ergotoxine produce a condition of immobility of the bladder. Expts. depending on the selective blocking of nerve impulses by these drugs are therefore of doubtful value.