Partial Expression of Genes and Some Proteins Associated with the Dopaminergic Phenotype in Vasopressinergic Neurons of the Supraoptic Nucleus in Intact Mice

Nearly forty years ago, it was first discovered that vasopressinergic neurons in the supraoptic nucleus contain tyrosine hydroxylase (TH), the first enzyme of dopamine synthesis. In some mammals, it is expressed only under stress, such as osmotic stimulation and so on (rats); in others it is expressed under normal conditions (tree shrews), and in a third group it is expressed in pathology (humans). This study is devoted to testing the hypothesis that vasopressinergic neurons may express some other proteins of the dopaminergic phenotype in addition to TH. To meet this aim, we assessed the expression of genes encoding proteins of the dopaminergic phenotype, such as TH, aromatic L-amino acid decarboxylase, vesicular monoamine transporter 2, and dopamine transporter, in vasopressin-immunopositive neurons of the supraoptic nucleus of intact C57BL/6 mice isolated by laser microdissection. We demonstrated that vasopressinergic neurons of the supraoptic nucleus express the genes for all of the aforementioned dopaminergic phenotype proteins, with the exception of the dopamine transporter. In a subsequent immunohistochemical study, evidence was obtained that, in addition to TH, some vasopressinergic neurons contain aromatic L-amino acid decarboxylase and, perhaps, vesicular monoamine transporter 2. Further studies are needed to determine whether the dopaminergic phenotype proteins we identified possess specific functional activity.