Action of formamidine pesticides on the octopamine receptors on locust fat body

Abstract

1. The action of two formamidines, chlordimeform (CDM) and desmethylchlordimeform (DCDM), on isolated fat body of locusts has been examined. 2. Treatment with DCDM resulted in a dose-dependent stimulation of lipid release while CDM was ineffective at 10 −4M. 3. The action of DCDM was blocked by the α-adrenergic receptor blocker phentolamine, but not by the β-blocker propranolol. 4. DCDM (5 × 10 −6 M) in the presence of a phosphodiesterase inhibitor caused a 4-fold elevation of cyclic AMP in the fat body; this response was blocked by phentolamine but not by propranolol. CDM (10 −5 M) did not alter cyclic AMP levels in the fat body. 5. The effects of octopamine (10 −5 M) and DCDM (10 −5 M) on cyclic AMP level were not additive. 6. It is concluded that DCDM (or its metabolites) act upon octopamine receptors on locust fat body while CDM has no effect. In view of the positive action of CDM on other octopamine receptors this indicates there may be differences between octopamine receptors of different tissues.