Phenyliminoimidazolidine Derivatives Activate Both Octopamine! and Octopamine2 Receptor Subtypes in Locust Skeletal Muscle

1. The actions of the phenyliminoimidazolidine derivatives, NC7 and NC5 on octopamine receptors in the extensor-tibiae neuromuscular preparation of the locust are described. 2. The derivatives activate both OCTOPAMINE, and OCTOPAMINE2 receptors in this preparation. They are not selective agonists of OCTOPAMINE2 receptors that activate adenylate cyclase. 3. The relative potencies of NC5 and NC7 on OCTOPAMINE, and OCTOPAMINE2 receptors differ, suggesting that they may be useful in the development of selective agonists that can distinguish between the different pharmacological subclasses of octopamine receptor. 4. The octopamine-mediated increases in cyclic AMP levels in this preparation can be separated into highand low-affinity components. NCS and NC7 appear to activate the high-affinity component of this response selectively.