Molecular cloning and tissue distribution of an avian D2 dopamine receptor mRNA from the domestic Turkey (Maleagris gallopavo)

The reverse transcriptase-polymerase chain reaction (RT-PCR), in combination with 5' and 3' rapid amplification of cDNA ends (RACE), was used to clone a G protein-coupled receptor from turkey brain mRNA. This cDNA clone has an open reading frame of 1,311 base pairs encoding a 436-residue protein with seven transmembrane-spanning domains and exhibits high homology with previously cloned mammalian D2 dopamine receptors. Northern blot analysis of turkey brain mRNA detected an approximate 2.4-kb transcript. RT-PCR and subsequent nucleotide sequence analysis of turkey brain and peripheral tissue mRNA also demonstrated the presence of an alternatively spliced mRNA corresponding to the predicted D2 short isoform. RT-PCR experiments demonstrated a widespread distribution of alternatively spliced D2 dopamine receptor transcripts throughout the turkey brain and in select peripheral tissues as well. In situ hybridization experiments detected strong autoradiographic signals over much of the turkey telencephalon, diencephalon, mesencephalon, cerebellum, pituitary, and pineal gland. Dopamine has several important functions as a neurotransmitter and hormone in mammals and may have similar actions in avian species. The cloning and tissue distribution of the D2 receptor subtype should enable the investigation of any functional role dopamine and dopamine receptors exert on the physiology and behavior of birds.