Imidacloprid impairs memory and brain metabolism in the honeybee (Apis mellifera L.)

Axel Decourtye, , a, Catherine Armengaudb, Michel Renouc, James Devillersd, Sophie Cluzeaue, Monique Gauthierb and Minh-Hà Pham-Delèguef

a ACTA, 18 avenue des Monts d’Or, 69890 La Tour de Salvagny, France
b Centre de Recherches sur la Cognition Animale, Université Paul Sabatier, 118 route de Narbonne, F-31062, Toulouse, France
c Unité de Phytopharmacie et Médiateurs Chimiques, INRA, Route de St. Cyr, F-78026, Versailles cedex, France
d CTIS, 3 chemin de la Gravière, F-69140, Rillieux La Pape, France
e ACTA, 149 rue de Bercy, F-75595, Paris cedex 12, France
f Laboratoire de Neurobiologie Comparée des Invertébrés, INRA, BP 23, La Guyonnerie, F-91440 Bures-sur-Yvette, France

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Abstract
Imidacloprid is a chloronicotinyl insecticide which interacts with insect nicotinic acetylcholine receptors. Thirty minutes after oral treatment of honeybees with imidacloprid, the olfactory learning performances in a proboscis extension reflex (PER) procedure were impaired. In parallel, an increase of the cytochrome oxidase labelling was found into the calyces of the mushroom bodies. Imidacloprid administered 15 min or 1 h after a one-trial conditioning of PER impaired the medium-term olfactory memory. By contrast, the short-term (30 s or 3 min conditioning-treatment time interval) and long-term (24 h conditioning-treatment time interval) memories were unaffected. The impairment of medium-term olfactory memory by imidacloprid is discussed in the context of neural circuits suspected to mediate memory formation in the honeybee brain.

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