First identification of dopamine receptors in pikeperch, Sander lucioperca, during the pre-ovulatory period

Dopamine (DA) is a ubiquitous neurotransmitter exerting a range of pleiotropic actions through two DA receptor families, the D1 and the D2. To date in vertebrates, a maximum of four receptor subtypes have been identified within the D1 family, D-1 (former D-1A), D-5 (former D-1B), D-6 (former D-1C and D-1D) and D-7 (former D-1E), while the D2 family encloses five subtypes, D-2, D-3, D-4, D-8 (former D-2like or D-2l) and D-9 (former D4-related sequence or D4-rs). In teleosts, no study has investigated in parallel all the DA receptors to identify and localize the whole receptor repertoire from both families. In pikeperch, Sander lucioperca, a species of interest for aquaculture development, the existence, number and location of the DA receptors are totally unknown. To address these questions, RNA-seq with de novo transcriptome reconstruction, functional annotation and phylogenetic analysis were performed to characterize the transcript repertoire of DA receptors in the brain of female pikeperch at the pre-ovulatory period. Ten different cDNA were identified and showed to belong to the D-1 family: two D-1, one D-5a, one D-6a and one D-6b and to the D2 family: two spliced variants of D-2, one D-3, one D-8 and one D-9. Unlike zebrafish, the subtypes D-4 and D-7 have not yet been isolated in pikeperch. As expected D-1, D-3, D-8 and D-9 are mostly expressed in brain parts except for the cerebellum (D-1 and D-3). The inter-species differences in the number of DA receptors and the inter-organ differences in the gene expression of all receptors support the complexity of the dopaminergic actions in vertebrate.