Prolonged electrical stimulation of the nipples evokes intermittent milk ejection in the anaesthetised lactating rat

Intermittent and continuous electrical stimulation of the nipples elicited milk-ejection responses in the lactating rat. The responses occurred intermittently, with similar amplitudes and periodicity as those seen in suckled rats. The responses were always associated with synchronization of the electroencephalogram (EEG), but some rats with synchronized EEG activity did not milk eject during stimulation. Since continuous stimulation also resulted in intermittent milk ejection it seems unlikely that the periodicity of the reflex in suckled rats depends upon changes in the intensity of sensory stimulation. The techniques of nipple stimulation may be a useful method with which to study neural pathways and other phenomena such as gating involved in oxytocin release and milk ejection. The success of the technique depends on a variety of factors such as parameters of the stimulation and state of anaesthesia.