Induction of the “stretching response” by vagino-cervical stimulation in the rat

This paper describes a “stretching response” which occurs in some female laboratory rats during the course of mating. It is most obviously characterized by an indentation of the abdominal wall and tonic limb and pelvic movements, which occur in irregularly spaced pulses of variable duration. The response was not seen in 10 rats in which intromissions had been prevented by a vaginal mask. In contrast, stretching was displayed by 9 of 10 non-masked subjects. This indicates that vagino-cervical stimulation is necessary for the induction of the stretching response. Vagino-cervical stimulation delivered by a plunger assembly was found to be sufficient to induce the response in 9 of 10 rats. Temporal summation of this stimulation was seen and ovarian hormones were found to increase the amount of stretching. Hypotheses concerning causes and effects of the stretching response are presented.