Cell‐Specific Expression of the Rat Oxytocin Gene in Transgenic Mice

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Abstract
The genes for the posterior pituitary hormones oxytocin (OT) and vasopressin (VP) are expressed in magnocellular neurons of the hypothalamus. Previous attempts to obtain cell‐specific expression of OT and VP transgenes in mice have been unsuccessful using constructs containing only the OT or VP genes. As the endogenous genes are located near each other on the same chromosome, we investigated four transgenic mouse lines incorporating a single 5.2 k bp construct of rat genomic deoxyribonucleic acid with 1.63 k bp and 3.55 k bp of the OT and VP genes, respectively. Rat OT transcripts were detected only in transgenic mouse OT neurons of the paraventricular and supraoptic nuclei in two lines. The levels of endogenous and transgene OT transcripts increased in response to 10 days of lactation. Furthermore, rat OT‐associated neurophysin immunoreactivity was detected in magnocellular cell bodies as well as in the posterior pituitary of the transgenic but not the control mice. Cell‐specific rat VP expression was not detected in these transgenic mice.