Studies on the biochemical mechanisms of anorexia caused by formamidine pesticides in the tobacco hornworm Manduca sexta

Abstract

Injection of the fifth-instar larvae of the tobacco hornworm Manduca sexta with 10 nmol octopamine (OA), chlordimeform (CDM) and N-demethylchlordimeform (DCDM) resulted in decreasing food consumption, body weight gain and production of fecal pellets. These phenomena were accompanied by elevation of hemolymph glucose, trehalose and total sugar levels. Phentolamine (PA) antagonized the elevation of hemolymph sugars caused by OA, CDM and DCDM in vitro. Furthermore, PA inhibited the activation of hemolymph sugar levels was not additive in vitro. These results support the notion that CDM DCDM on hemolymph sugar levels was not additive in vivo. These results support the notion that CDM or its metabolic activation to DCDM acts on the OA receptor of the tobacco hornworm larvae as has been shown in other insects. Such a rise in hemolymph sugars may be one of the biochemical causes for the CDM-induced antifeeding activity and anorexia in this species.