Identification of multiple vasotocin receptor cDNAs in teleost fish: Sequences, phylogenetic analysis, sites of expression, and regulation in the hypothalamus and gill in response to hyperosmotic challenge

Vasopressin and its homolog vasotocin regulate hydromineral balance, stress responses, and social behaviors in vertebrates. In mammals, the functions of vasopressin are mediated via three classes of membrane-bound receptors: V1a-type. V1b-type and V2-type To date, however, only a single class of vasotocin receptor has been identified in teleost fish Here, cDNAs encoding three putative vasotocin receptors - two distinct Via-type receptor paralogs (V1a1 and V1a2) and a previously undescribed V2-type receptor (V2) - and a single isotocin receptor were isolated and sequenced from the Amargosa pupfish (Cypnnodon nevadensis amargosae). RT-PCR revealed that mRNAs for these receptors differed in expression patterns with Vial mRNAs abundant in the brain, pituitary and testis. V1a2 transcripts at greatest levels in brain, heart and muscle. V2 transcripts most common in the gills, heart and kidney, and isotocin receptor mRNAs abundant in the midbrain, pituitary and gonads In response to an acute hyperosmotic challenge, pro-vasotocin and V2 mRNA levels in the hypothalamus decreased, while transcripts of Vial in the hypothalamus and V1a2 in the gills increased Partial transcripts for structurally related V2-type, as well as multiple Via-type, receptors were also identified in other teleosts, suggesting that multiple vasotocin receptors may be present in many Actinopterygn fishes (C) 2010 Elsevier Ireland Ltd. All rights reserved.