**Oxytocin and Myometrial Contractility in Labor**

N. Vrachnis1, F.M. Malamas2, S. Sifakis3, A. Parashaki4, Z. Iliodromiti1, D. Botsis1 and G. Creatsas1 *12nd Department of Obstetrics and Gynecology, University of Athens Medical School, Aretaieio Hospital, Athens, 21st Department of Obstetrics and Gynecology, University of Athens Medical School, Alexandra Hospital, Athens, 3Department of Obstetrics and Gynaecology, University Hospital of Heraklion, Crete, 4Health Center of Thira, Thira, Greece* 

### **1. Introduction**

242 From Preconception to Postpartum

Quenby S et al. (2004). "Dysfunctional labor and myometrial lactic acidosis." Obstet Gynecol

Akerud H et al. (2009), 'Lactate distribution in culture medium of human myometrial

Endocrinology and metabolism, 297 (6), E1414-9.

biopsies incubated under different conditions', American journal of physiology.

103(4): 718-23.

Oxytocin (OT), a hormone exerting central and peripheral actions, plays an essential role in the mechanisms of parturition and lactation. It acts through its receptors, the number of which increases in the uterus towards labor, thus augmenting the uterotonic effect. Activated oxytocin receptors (OTR) by oxytocin, signal via a large number of intracellular pathways causing increased myometrial contractions by means of increased intracellular Ca+2 ion, increased myosin light chain phosphorylation and increased production of prostaglandins.

Molecules that antagonize the action of oxytocin have been developed for use as tocolytic agents in the treatment of preterm labor. One presently available tocolytic, the oxytocin receptor antagonist atosiban, acts on both myometrial and decidual OTRs. However, research is in progress aimed at the development and clinical application of new oxytocin receptor antagonists with an enhanced pharmacological profile translating as higher affinity for the receptor as well as better bioavailability and improved safety. In this chapter we describe the function of oxytocin in labor and review the use of atosiban for the treatment of preterm labor, while also evaluating the current development of other OTR antagonists that are potential candidates as tocolytic drugs in the future.
