[en] Ontogenesis of oxytocin (OT) and vasopressin (VP) gene expression and function were investigated in murine thymus. OT and VP transcripts were detected in the thymus on embryonic days 13 and 15, respectively. Corresponding messenger RNAs were evidenced in thymic epithelial cells by in situ hybridization with a neurophysin probe. From all OT and VP receptors, only OTR was expressed by all T-cell subsets, while V1bR was found in double positive and single positive CD8 cells. In fetal thymic organ cultures, OTR antagonist d[DTyr(Et)(2), Thr(4)]OVT increased early apoptosis of CD8 cells, while V1bR antagonist (Sanofi SSR 149415) inhibited T-cell differentiation, and favored CD8 T-cell commitment. (C) 2004 Elsevier B.V. All rights reserved.