Organization of the nervous control of urethral sphincter. A study in the anaesthetized cat with intact central nervous system.

The electromyographic response of the striated urethral sphincter has been evoked following stimulation of its motor nerve, the pudic nerve. Stimulation of the intact nerve fires the muscular fibres directly with a latency of approximately 1.2 msec and also in a reflex manner via the ipsilateral and contralateral pathways. The two paths transmit the reflex responses with a minimal latency of 8--10 msec (chloralose). During Halothane anaesthesia the reflex appears with a longer latency (up to 26 msec). The variability of this latency and the central delay of around 5 msec agree well with a polysynaptic central pathway. The reflex response is generally composed of an early wave of large amplitude followed by an afterdischarge lasting (between 30--60 msec) and of higher threshold. This response is triggered by the fastest afferents in the pudic nerve. The excitability of the motoneurones controlling the sphincter was tested by the double shock method and was shown to be analogous to other somatic motoneurones. The electrically evoked reflex response is slightly inhibited by bladder distension. A more powerful type of inhibition of the sphincter activity is associated with activation of the bladder motor centre.