QUANTITATIVE-ANALYSIS OF DOPAMINE-RECEPTOR MESSAGES IN THE MOUSE COCHLEA

Dopamine receptor isoforms were examined in the cochlea of the CBA, mo use by RT-PCR analysis and nucleotide sequencing, utilizing primers sp ecific for known dopamine receptor isoforms. Cochlear cDNA sequences c orresponding to dopamine D-2(long) and D-3 receptors were amplified, w hereas those representing D-1A, D-1B, D-2(short), and D-4 were not det ected. Utilizing quantitative competitive PCR analysis, relative level s of dopamine receptor transcripts were found to be 0.002, 0.014, 0.01 6, and 1.000 for D-2(long) cochlea, D-3 cochlea, D-3 brain, and D-2(lo ng) brain, respectively. In the context of previously published findin gs, the current work provides key quantitative evidence necessary to e stablish that dopamine is a neurotransmitter in the auditory inner ear .