In the previous papers two antagonistic areas in the pons concerning micturition, the pontine detrusor nucleus (PDN) and the pontine urine-storage nucleus (PUSN), were reported. In the present paper the interference between these two pontine areas was investigated by means of electromyogram of the external urethral sphincter. The conclusions are as follows:
1. PDN stimulation elicits strong vesical contraction with simultaneous disappearance of discharge from the external urethral sphincter.
2. In the resting bladder, stimulation of PUSN results in an increase of discharge from the external urethral sphincter despite the absence of recognizable change in the intravesical pressure.
3. If during the long-lasting PDN stimulation PUSN is stimulated for a while, sphincter discharge reappears with the inhibition of the rise of the intravesical pressure corresponding to the period of PUSN stimulation. This phenomenon can be observed also in bladderless preparations.
4. The significance of this interference for micturition and urine-storage was discussed in detail.