title: The dopamine D2 receptor gene in lamprey, its expression in the striatum and cellular effects of D2 receptor activation.
abstract: All basal ganglia subnuclei have recently been identified in lampreys, the phylogenetically oldest group of vertebrates. Furthermore, the interconnectivity of these nuclei is similar to mammals and tyrosine hydroxylase-positive (dopaminergic) fibers have been detected within the input layer, the striatum. Striatal processing is critically dependent on the interplay with the dopamine system, and we explore here whether D2 receptors are expressed in the lamprey striatum and their potential role. We have identified a cDNA encoding the dopamine D2 receptor from the lamprey brain and the deduced protein sequence showed close phylogenetic relationship with other vertebrate D2 receptors, and an almost 100% identity within the transmembrane domains containing the amino acids essential for dopamine binding. There was a strong and distinct expression of D2 receptor mRNA in a subpopulation of striatal neurons, and in the same region tyrosine hydroxylase-immunoreactive synaptic terminals were identified at the ultrastructural level. The synaptic incidence of tyrosine hydroxylase-immunoreactive boutons was highest in a region ventrolateral to the compact layer of striatal neurons, a region where most striatal dendrites arborise. Application of a D2 receptor agonist modulates striatal neurons by causing a reduced spike discharge and a diminished post-inhibitory rebound. We conclude that the D2 receptor gene had already evolved in the earliest group of vertebrates, cyclostomes, when they diverged from the main vertebrate line of evolution (560 mya), and that it is expressed in striatum where it exerts similar cellular effects to that in other vertebrates. These results together with our previous published data (Stephenson-Jones et al. 2011, 2012) further emphasize the high degree of conservation of the basal ganglia, also with regard to the indirect loop, and its role as a basic mechanism for action selection in all vertebrates.
authors.affiliation: Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Brita
authors.initials: B
authors.lastname: Robertson
authors.forename: Icnelia
authors.initials: I
authors.lastname: Huerta-Ocampo
authors.forename: Jesper
authors.initials: J
authors.lastname: Ericsson
authors.forename: Marcus
authors.initials: M
authors.lastname: Stephenson-Jones
authors.forename: Juan
authors.initials: J
authors.lastname: Pérez-Fernández
authors.forename: J Paul
authors.initials: JP
authors.lastname: Bolam
authors.forename: Rochellys
authors.initials: R
authors.lastname: Diaz-Heijtz
authors.forename: Sten
authors.initials: S
authors.lastname: Grillner
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003342:Corpus Striatum / Q000378:metabolism*; D019143:Evolution, Molecular; D005260:Female; D005786:Gene Expression Regulation; D007798:Lampreys / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D017448:Receptors, Dopamine D2 / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D017448:Receptors, Dopamine D2; D014446:Tyrosine 3-Monooxygenase