Two human alpha 2-adrenoceptor subtypes alpha 2A-C10 and alpha 2B-C2 expressed in Sf9 cells couple to transduction pathway resulting in opposite effects on cAMP production.

The baculovirus expression vector system utilizing the strong polyhedrin gene promoter of the Autographa californica nuclear polyhedrosis virus (AcNPV) was used for high level expression of the two alpha 2-adrenoceptor subtypes alpha 2A-C10 and alpha 2B-C2 in Spodoptera frugiperda (Sf-9) insect cells. For rapid screening of recombinant viruses the luciferase gene was expressed under the early ETL-promoter (early transcript large) in the same plasmid. Both receptor subtypes showed the same rank order of binding affinity for four agonists tested: dexmedetomidine > l-medetomidine = clonidine > noradrenaline. For the alpha 2A-C10 subtype, these agonists inhibited forskolin stimulated cAMP production through pertussis toxin sensitive G-proteins. In contrast, for the alpha 2B-C2 subtype the agonists stimulated both basal and forskolin stimulated cAMP production.