Oxytocin receptor gene expression in rat mammary gland: structural characterization and regulation.

The differential, tissue-specific regulation of oxytocin (OT) binding sites allows the neurohypophysial nonapeptide OT to fulfill a dual role: to induce uterine contractions at parturition and to mediate milk ejection during lactation. Whereas uterine OT binding sites are up-regulated prior to parturition and are rapidly down-regulated thereafter, mammary gland OT binding sites gradually increase throughout gestation and remain up-regulated during the ensuing lactation period. Here, we structurally characterized OT receptor (OTR) mRNA in mammary gland and analyzed its expression during gestation and lactation and in response to steroid treatment.

Pharmacological characterization of oxytocin-binding sites in rat spinal cord membranes: comparison with embryonic cultured spinal cord neurones and astrocytes.

Detection and pharmacological characterization of OT-binding sites were performed on 12-day-old rat spinal cord membranes and on embryonic cultured spinal neurones and astrocytes after 12 days in culture. In neurone-enriched cultures, OT-binding sites were detected by autoradiography on cells morphologically comparable to neurone-specific enolase immunoreactive cells. In astrocyte cultures, as shown by combination of autoradiography and immunocytochemistry, OT-binding sites were detected on cells expressing the glial fibrillary acidic protein (a specific astrocytic marker).

Downregulation of the oxytocin receptor on cultured astroglial cells.

Cultured astroglial cells obtained from rat fetal hypothalamus express oxytocin (OT) receptors, which have been previously characterized (Di Scala-Guenot and Strosser. Biochem. J.

Increase of intracellular calcium induced by oxytocin in hypothalamic cultured astrocytes.

A recent study demonstrated oxytocin (OT) receptors on hypothalamic cultured astrocytes (Di Scala-Guenot and Strosser, 1992). The attempt in the present paper was to determine a possible intracellular calcium mobilization induced by OT receptor activation in these cells. Using the microspectrofluorimetric technique with fura-2, as calcium indicator, brief applications of OT on single astrocytes induced a transient and reversible dose-dependent increase of intracellular calcium concentration ([Ca2+]i) in most of the cells tested.