[Some newer findings concerning oxytocin receptor signaling]

Nonapeptide oxytocin (OT) is known primarily as an inducer of uterine contraction and milk ejection. Recently, there have been described its regulatory actions on various brain functions and on many peripheral actions including regulation of cell growth. The diversity of OT actions produced by the stimulation of OT receptors (OTR) is paralleled by a diversity of its signaling pathways. OTR belongs to the G-protein coupled receptors (GPCR) and unlike the receptors for vasopressin its actions are mediated by only one type of receptor. However, its actions are influenced by the location of OTR in the plasma membrane and its relationship to the membraneous lipid rafts. The occupation of OTR in different locations in plasma membrane determines the signaling pathway. Persistent activation of MAP kinases leads through nuclear mechanisms to the inhibition of cell growth while the transient activation is responsible for stimulation of cell growth. The review covers many areas of OTR signaling, including activation of orthosteric and allosteric sites on receptors, new signaling pathway utilizing various MAP kinases, stimulation of prostaglandine synthesis etc. The elucidation of the novel signaling pathways will help to develop new drugs influencing specific sites on OT signaling that may be used as agonists or antagonists in clinical therapy. Moreover, these new discoveries may represent a contribution for the knowledge of physiology and pharmacology not only of oxytocin receptor but also other GPCR.