Postnatal expression of V2 vasopressin receptor splice variants in the rat cerebellum

The V2 vasopressin receptor gene contains an alternative splice site in exon-3, which leads to the generation of two splice variants (V2a and V2b) first identified in the kidney. The open reading frame of the alternatively spliced V2b transcript encodes a truncated receptor, showing the same amino acid sequence as the canonical V2a receptor up to the sixth transmembrane segment, but displaying a distinct sequence to the corresponding seventh transmembrane segment and C-terminal domain relative to the V2a receptor. Here, we demonstrate the postnatal expression of V2a and V2b variants in the rat cerebellum. Most importantly, we showed by in situ hybridization and immunocytochemistry that both V2 splice variants were preferentially expressed in Purkinje cells, from early to late postnatal development. In addition, both variants were transiently expressed in the neuroblastic external granule cells and Bergmann fibers. These results indicate that the cellular distributions of both splice variants are developmentally regulated, and suggest that the transient expression of the V2 receptor is involved in the mechanisms of cerebellar cytodifferentiation by AVP. Finally, transfected CHO-K1 expressing similar amounts of both V2 splice variants, as that found in the cerebellum, showed a significant reduction in the surface expression of V2a receptors, suggesting that the differential expression of the V2 splice variants regulates the vasopressin signaling in the cerebellum.