THE EXPRESSION OF A CLONED DROSOPHILA OCTOPAMINE TYRAMINE RECEPTOR INXENOPUS OOCYTES/

The expression of a cloned Drosophila octopamine/tyramine receptor (Oc tyR99AB) is described in Xenopus oocytes. Agonist stimulation of OctyR 99AB receptors increased intracellular Ca2+ levels monitored as change s in the endogenous inward Ca2+-dependent chloride current. The recept or is preferentially sensitive to biogenic amines with a single hydrox yl on the aromatic ring. The G-protein, G(alpha i), appears to be invo lved in the coupling of the receptor to the production of intracellula r calcium signals, since the effect is pertussis-toxin sensitive and i s blocked or substantially reduced in antisense knockout experiments u sing oligonucleotides directed against G(alpha i) but not by those dir ected against G(alpha o), G(alpha q), and G(alpha 11).G alpha 11. The increase in intracellular calcium levels induced by activation of the OctyR99AB receptor can potentiate the ability of activation of a co-ex pressed beta(2)-adrenergic receptor to increase oocyte cyclic AMP leve ls. A comparison of the pharmacological coupling of OctyR99AB to diffe rent second messenger systems when expressed in Xenopus oocytes with p revious studies on the expression of the receptor in a Chinese hamster ovary cell line suggests that the property of agonist-specific coupli ng of the receptor to different second messenger systems may be cell-s pecific, depending upon the G-protein environment of any particular ce ll type. (C) 1997 Elsevier Science B.V.