Effects of tutin and its derivatives on GAD and GABA-T in Pseudelatia separata (Lepidoptera: Noctuidae) Efectos de tutin y sus derivados en el GAD y GABA-T en Pseudelatia separata (Lepidoptera: Noctuidae)

Tutin inhibits the receptors of the neurotransmitter γ-aminobutyric acid (GABA). In this work, we compared tutin with its derivatives, 2-(4-methoxybenzoyloxy)-tutin (T1), 2-(3,5-dinitrobenzoyloxy)-tutin (T2), 2-(6-chloronicotinoyloxy)-tutin (T3), and 2-(4-nitrobenzoyloxy)-tutin (T4), in terms of their effects on feeding and the feedback regulation mechanism of GABA metabolism. Spectrophotometry was used to determine the glutamic acid decarboxylase (GAD) and γ-aminobutyric acid transaminase (GABA-T) activities of these compounds in 3rd instar larvae of Pseudelatia separata. Clear antifeedant activities were manifested by T1 and especially T3, whereas T4 stimulated feeding in P. separata. GAD and GABA-T activities in larvae treated with all five toxins differed significantly from the control and from one other (P < 0.05) in terms of treatment types and exposure times. The effects of the toxins on GAD and GABA-T were time-dependent for 48 h. GAD activities were inhibited by tutin, T2, T3, and T4, and were enhanced by T1. GABA-T activities were increased by all the toxins in varying degrees. Variation of GABA content in P. separata larvae resulted from the disturbance of GAD and GABA-T by tutin and its derivatives. Results suggest that T3, with its nicotinoyl group, is the most promising novel active ingredient for pest control. La tutina inhibe los receptores del neurotransmisor acido γ-aminobutírico (GABA). En esta publicación se compara la tutina con sus derivados, 2-(4-metoxibenzoiloxi)-tutina (T1), 2-(3,5-dinitrobenzoyloxy)-tutina (T2), 2-(6-chloronicotinoyloxy)-tutina (T3), y 2-(4-nitrobenzoiloxi)-tutina (T4), en términos de sus efectos sobre la alimentación y el mecanismo de regulación de la retroalimentación del metabolismo del GABA. Se usó espectrofotometría para determinar la actividad de descarboxilasa del ácido glutámico (GAD) y γ-aminobutírico ácido transaminasa (GABA-T) en las larvas del tercer estadio de Pseudelatia separata. Actividades antialimentarias se manifiestan en T1 y especialmente en T3, mientras que T4 estimula la alimentación en P. separata. GAD y GABA-T difieren significativamente en las actividades de las larvas tratadas con las cinco toxinas, tanto en el control como ente ellas (P < 0.05) en cuanto a tipos de tratamiento y tiempos de exposición. Los efectos de las toxinas en el GAD y GABA-T dependieron del tiempo durante 48 h. Las actividades de GAD fueron inhibidos por la tutina, T2, T3 y T4, y se mejoraron con T1. Las actividades de GABA-T se incrementaron en todas las toxinas en diferentes grados. Variación del contenido de