Identification of Uridine 5'-triphosphate Receptor mRNA in Rat Cochlear Tissues

Abstract

Previous investigations have reported the presence of uridine 5'-triphosphate (UTP) and adenosine 5'-triphosphate (ATP) receptors triggering phospholipase C (PLC) activation in the frog semicircular canal. The aim of this work was to characterize the molecular subtypes of these nucleotide receptors. Due to the lack of molecular tools for purinoceptors in amphibia, this study was performed on the rat. The stria vascularis, organ of Corti and spiral ligament were microdissected from Long Evans rat cochlea. RNA was extracted from four cochleas and polymerase chain reaction (PCR) was performed after reverse transcription (RT) using oligonucleotides for sequences of P2Y₁, P2Y₂, P2Y₄ and P2Y₆ receptors. Various tissues were used as negative controls (testis for P2Y₁ and P2Y₆ receptors, brain for P2Y₂ and P2Y₄ receptors and liver for P2Y₄ receptors). Data show the expression of the four transcripts in the stria vascularis, organ of Corti and spiral ligament. When results were normalized to the signal obtained with S14 mRNA, a ribosomal protein used as an internal standard, expressions were similar in the three structures. In conclusion, these results demonstrate the mRNA expression of the three UTP receptors (P2Y₂, P2Y₄ and P2Y₆) and of the P2Y₁ ATP receptor in both sensory and secretory structures of the rat inner ear. Their functional roles remain to be defined.