URETHRAL BEHAVIORS DURING MICTURAL REFLEX ON THE DECEREBRATED FEMALE DOG

Abstract

Physiologic experiments were carried out on decerebrated female dogs for the purpose of studying the urethral behaviors during mictural reflex. The bladder pressure was recorded simultaneously with internal and external urethral sphincter pressures, internal urethral sphincter movements in both longitudinal and transverse directions with strain gauge force transducers and external urethral sphincter electromyography. The rectal pressure was also recorded as a monitor of intraabdominal pressure.
1) In the decerebrated preparation, a powerfull detrusor contraction was elicited by both slow filling of bladder with water and inflation of an intravesical latex balloon.
2) The pressure in the internal sphincter dropped simultaneously with detrusor contraction elicited by balloon inflation. This pressure change was still observed after vesicourethral separation. However, the degree of the pressure drop was significantly reduced by disconnection of the bladder and urethra.
3) The pressure drop in the internal sphincter was not diminished after treatment with succinylcholine chloride and was not so influenced by administration of propranolol (1mg i. a.). But, it could hardly be distinguished after transection of hypogastric nerves or administration of phentolamine (1mg. i. a.).
4) The movements of internal sphincter did not have a definite tendency when measured by a pair of extraluminal strain gauge force transducers.
5) The pressure drop in the external sphicter occurred gradually before any rise in the bladder pressure, at the initiation of voiding. The electromyography of external urethral sphicter also demonstrated prevoiding decrease of the electroactivity. After treatment with succinylcholine chloride the prevoiding pressure drop could not be observed.
These results demonstrate that the pressure drop in the internal sphincter is depended on the nerve reflex and further reinforced by the vesicourethral muscle continuity. In addition, it is suggested that the nerve reflex is mediated by the hypogastric nerve and mainly controlled by the alpha-adrenergic receptor mechanism.