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 h ave a role in prenatal development, we have studied the mRNA expressio n and distribution of these receptors during murine embryonic developm ent, Using RT-PCR on RNA from embryos taken at progressive stages of d evelopment, we have shown that the D-3 receptor is expressed significa ntly earlier than the D-2 receptor, being detectable at day 9.5 post-c onception (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 tr anscripts were first detected at day 9.5 p.c, in the ventral aspect of the anterior neural tube, whereas D-2 receptor transcripts first appe ared a day later. By day 10.5-11.5 p.c. both D-3 and D-2 receptor tran scripts were present in the developing forebrain, and later also in th e branchial arches and along the prospective vertebral column, The ear ly appearance of the D-3 subtype in murine development and its predomi nance over the D-2 subtype suggest that the D-3 receptor may have a fu nctional role in prenatal development.