THE SENSORY BUT NOT MUSCULAR PELVIC NERVE BRANCH IS NECESSARY FOR PARTURITION IN THE RAT

In the rat the pelvic nerve consists of a viscerocutaneous (sensory) b ranch which receives information from pelvic viscera and the midline p erineal region, and a somatomotor (muscular) branch which innervates t he ilio-and pubococcygeous muscles. To investigate the contribution of these branches to the parturition process, the length of gestation an d course of delivery were closely monitored in 43 pregnant, Wistar-str ain rats randomly assigned to five groups: untreated control animals, animals in which the somatomotor branch of the pelvic nerve was bilate rally sectioned on Day 14 of gestation, animals in which the viscerocu taneous branch of the pelvic nerve was bilaterally sectioned on Day 14 of gestation, animals treated similarly to the previous group but wit h young delivered by C-section at term, and sham-operated controls. Se ctioning the viscerocutaneous branch seriously disrupted parturition a nd resulted in major dystocia and a high percentage of stillbirths in all females. In contrast, sectioning the somatomotor branch had no app arent effect on parturition and no significant differences were found between females of this group and sham or control dams on any of the m easures recorded. IL is concluded that the viscerocutaneous branch of the pelvic nerve is vital for the normal course of parturition in the rat but that the somatomotor branch plays little role, if any. (C) 199 8 Elsevier Science Inc.