α1-Adrenoreceptor in human hippocarnpus:: Binding and receptor subtype mRNA expression

alpha(1)-Adrenoreceptors (AR), of which three subtypes exist (alpha(1A)-, alpha(1B)- and alpha(1D)-AR) are G-protein-coupled receptors that mediate the actions of norepinephrine and epinephrine both peripherally and centrally. In the CNS, alpha(1)-ARs are found in the hippocampus where animal studies have shown the ability of alpha(1)-AR agents to modulate long-term potentiation and memory; however, the precise distribution of alpha(1)-AR expression and its subtypes in the human brain is unknown making functional comparisons difficult. In the human hippocampus, 3 H-prazosin (a(1)-AR antagonist) labels only the dentate gyrus (molecular, granule and polymorphic layers) and the stratum lucidum of the CA3 homogenously. Human alpha(1A)-AR mRNA in the hippocampus is observed only in the dentate gyrus granule cell layer, while alpha(1D)-AR mRNA expression is observed only in the pyramidal cell layers of CA1, CA2 and CA3, regions where 3 H-prazosin did not bind. alpha(1B)-AR mRNA is not expressed at detectable levels in the human hippocampus. These results confirm a difference in hippocampal alpha(1)-AR localization between rat and humans and further describe a difference in the localization of the alpha(1A)- and alpha(1D)-AR mRNA subtype between rats and humans. Published by Elsevier B.V.