Comparison of the two methods of electroejaculation in the Japanese monkey (Macaca fuscata)

Electrical parameters in two methods of stimulation, i. e. the rectal probe method under anesthesia and the penile method in consciousness, were examined in the Japanese monkey (Macaca fuscata). In rectal probe method, ejaculation occurred in almost all animals by the stimulation of intermittent charges of 10-15 volts at a frequency of between 3-5 impulses per second by using a monophasic alternating current of 60 cycles. In penile method, good results were obtained by a DC, square wave stimulus applied with a frequency of 18-20 pulses per second and a duration of 20 milli-seconds per pulse. Animals required some training period for the penile method initially, but they responded well after sufficient practices. Although the semen samples obtained by the penile method showed spontaneous liquefaction partially at all times, samples by the rectal probe method frequently stayed in absolute coagulum. The fluid portion in the specimen by the penile method contained free, motile and rich spermatozoa in contrast with the rectal probe method that included little sperm in it. The details of stimulation and the observation of liquefaction are presented and discussed.