Pharmacological characterization of a Bombyx mori α-adrenergic like octopamine receptor stably expressed in a mammalian cell line

Abstract

Series of agonists and antagonists were examined for their actions on a Bombyx mori α-adrenergic-like octopamine receptor (OAR) stably expressed in HEK-293 cells. The rank order of potency of the agonists was clonidine > naphazoline > tolazoline in Ca2+ mobilization assays, and that of the antagonists was chlorpromazine > yohimbine. These findings suggest that the B. mori OAR is more closely related to the class-1 OAR in the intact tissue than to the other classes. N'-(4-Chloro-o-tolyl)-N-methylformamidine (DMCDM) and 2-(2,6-diethylphenylimino)-imidazolidine (NC-5) elevated the intracellular calcium concentration ([Ca2+]i) with EC50s of 92.8 μM and 15.2nM, respectively. DMCDM and NC-5 led to increases in intracellular cAMP concentration ([cAMP]i) with EC50s of 234nM and 125nM, respectively. The difference in DMCDM potencies between the cAMP and Ca2+ assays might be due to "functional selectivity." The Ca2+ and cAMP assay results for DMCDM suggest that the elevation of [cAMP]i, but not that of [Ca2+]i, might account for the insecticidal effect of formamidine insecticides. © 2010 Wiley Periodicals, Inc.