科研之友
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摘要
As the counterparts of the vertebrate adrenergic transmitters, octopamine and tyramine are important physiological regulators in invertebrates. They control and modulate many physiological and behavioral functions in insects. In this study, we reported the pharmacological properties of a new alpha 2-adrenergic-like octopamine receptor (CG18208) from Drosophila melanogaster, named DmOct alpha 2R. This new receptor gene encodes two transcripts by alternative splicing. The long isoform DmOct alpha 2R-L differs from the short isoform DmOct alpha 2R-S by the presence of an additional 29 amino acids within the third intracellular loop. When heterologously expressed in mammalian cell lines, both receptors were activated by octopamine, tyramine, epinephrine and norepinephrine, resulting in the inhibition of CAMP production in a dose dependent manner. The long form is more sensitive to the above ligands than the short form. The adrenergic agonists naphazoline, tolazoline and clonidine can stimulate DmOct alpha 2R as full agonists. Surprisingly, serotonin and serotoninergic agonists can also activate DmOct alpha 2R. Several tested adrenergic antagonists and serotonin antagonists blocked the action of octopamine or serotonin on DmOct alpha 2R. The data presented here reported an adrenergic-like G protein-coupled receptor activated by serotonin, suggesting that the neurotransmission and neuromodulation in the nervous system could be more complex than previously thought.
