Action of 2-aryliminothiazolidines on octopamine-sensitive adenylate cyclase in the American cockroach nerve cord and on the two-spotted spider mite Tetranychus urticae koch

The effects of 2-(2,6-diethylphenylimino)thiazolidine (HSO-783) and 2-(4-chloro-2-methylphenylimino)thiazolidine (HSO-786) were compared with those of 2-(2,6-diethylphenylimino)imidazolidine (NC-5) and 2-(4-chloro-2-methylphenylimino)oxazolidine (AC-6) in stimulating adenylate cyclase of Periplaneta americana ventral nerve cord homogenates. These activities were nonadditive with respect to the activity of a maximally effective concentration of octopamine. Washing of homogenates of ventral nerve cord incubated with NC-5, HSO-783, AC-6, and HSO-786 removed nearly all of the stimulatory activities of these agonists. Maximal stimulation of nerve cord adenylate cyclase activity by NC-5, HSO-783, AC-6, and HSO-786 was inhibited by several antagonists, including mianserin, cyproheptadine, chloromazine, and gramine. The rank-order ability of these antagonists to block the maximal adenylate cyclase activation by NC-5, HSO-783, AC-6, and HSO-786 was identical to the rank-order ability of the same antagonists to block the enzyme activation by an optimally effective concentration of octopamine. The β-adrenergic antagonist propranolol was less potent in this respect. AC-6 was a much better acaricide than HSO-783, HSO-786, and NC-5, which were much less potent octopaminergic agonists than AC-6. HSO-786 was a more potent acaricide and octopaminergic agonist than HSO-783. These observations suggest that the toxicity of NC-5, HSO-783, AC-6, and HSO-786 may be due to their octopaminergic agonist action.