Early expression of D-3 dopamine receptors in murine embryonic development

In order to determine Whether the D-2 and D-3 dopamine receptors may have a role in prenatal development, we have studied the mRNA expression and distribution of these receptors during murine embryonic development, Using RT-PCR on RNA from embryos taken at progressive stages of development, we have shown that the D-3 receptor is expressed significantly earlier than the D-2 receptor, being detectable at day 9.5 post-conception (p.c.), compared with day 13.5 p.c. for the D-2 subtype. We have also examined the mRNA distribution of the two receptors by,whole mount in situ hybridisation. In agreement with the PCR assays, the D-3 receptor was expressed earlier than the D-2 sybtype. D-3 receptor transcripts were first detected at day 9.5 p.c, in the ventral aspect of the anterior neural tube, whereas D-2 receptor transcripts first appeared a day later. By day 10.5-11.5 p.c. both D-3 and D-2 receptor transcripts were present in the developing forebrain, and later also in the branchial arches and along the prospective vertebral column, The early appearance of the D-3 subtype in murine development and its predominance over the D-2 subtype suggest that the D-3 receptor may have a functional role in prenatal development.