EXPRESSION OF DOPAMINE D2-RECEPTOR MESSENGER-RNA ISOFORMS AT THE PERIPHERAL CHEMOREFLEX AFFERENT PATHWAY IN DEVELOPING RABBITS

The two isoforms of dopamine D2 receptor, D2 short (D2(s)) and D2 long , are generated by alternative splicing of premessenger RNA and differ in the length of their third cytoplasmic loop. Expression of these tw o isoforms has not yet been studied at the level of the peripheral art erial chemoreflex pathway. Using reverse transcriptase-polymerase chai n reaction, we evaluated the relative abundance of dopamine D2 recepto r mRNA by amplifying a common segment between both D2 receptor mRNA is oforms which reflects the total D2-receptor mRNA and the two isoforms in the carotid bodies, the petrosal ganglia, and the superior cervical ganglia of 1-, 10-, and 25-day-old and adult rabbits. GH4C1 cell line , which does not express D2 receptors, was used as negative control, w hereas GH4C1 19 cell line, which expresses only the D2(s) mRNA and the striatum of each age, were used as positive controls. Both D2-recepto r mRNA isoforms were found to be expressed in all organs studied of ne wborn and adult rabbits. The expression of total D2 receptor mRNA in 1 0- and 25-day-old and adult rabbits was found to be 3-, 5-, and 1.5-fo ld more, respectively, compared with 1-day-old rabbits for all organs studied. Our data suggest that the expression of D2-receptor mRNA is m odulated with age at the level of the peripheral arterial chemoreflex pathway.