Evidence for the presence of the spinal pattern generator involved in the control of the genital ejaculatory pattern in the female rat

Substantial progress has been made during recent years in elucidating the control of male ejaculatory function by the central nervous system. These efforts have revealed the participation of a central pattern generator in the control of ejaculation. There is a strong similarity in the neural organization of male and female sexual functions. In the present study, the hypothesis that the spinal generator for ejaculation was present and functional in the female rat was evaluated. To this purpose, the expression of the ejaculatory motor pattern and its pharmacological activation in spinally transected female rats were investigated. Results revealed the presence in females of the already described rhythmic ejaculatory motor pattern of male rats. This ejaculatory motor pattern could be registered in the urethralis muscle of the female rat after mechanical stimulation of the urethra, vagina and clitoris and consisted, as in the male rat, of a first ejaculatory motor train followed by an after-discharge component. Besides, the female genital ejaculatory motor pattern could be pharmacologically induced by the systemic injection of sodium nitroprusside with similar motor characteristics. No significant differences between the sensorial and pharmacologically induced female genital motor patterns were found. Present findings provide evidence for the presence of the genital motor pattern of ejaculation in female rats and suggest that the spinal generator for ejaculation is also present and functional in this gender.