Chapter 24 Oxytocin in parturition of guinea pigs, humans, and other species

Abstract

This chapter discusses oxytocin in parturition of guinea pigs, humans, and other species. Oxytocin is unlikely to have a regulatory role in the onset of labor in guinea pigs. This is suggested by the lack of any influence of oxytocin receptor blockade on the timing of the onset of labor, the lack of any significant change in the binding characteristics of myometrial oxytocin receptors, and the gradual, and not sudden, increase in the oxytocin dose-response toward term. The fact that oxytocin is an unlikely trigger of labor is not limited to guinea pigs. In rats, oxytocin receptor blockade had no effect on gestational length at doses that inhibited the response to exogenous oxytocin. In women, oxytocin receptor density in myometrium does not increase significantly, plasma concentrations of oxytocin do not increase markedly, and oxytocin peptide in intrauterine tissues do not change at the onset of labor. Birth is a vital event for both offspring and parturient. Although oxytocin is not the trigger of labor in guinea pigs, it is indispensable for the normal progress of labor. Without oxytocin, the survival of this species would be in jeopardy.