Imidacloprid-Induced Facilitation of the Proboscis Extension Reflex Habituation in the Honeybee

摘要

Imidacloprid is a new insecticide from the family of the neonicotinoids, which interact with the insect nicotinic acetylcholine receptor. The effects of imidacloprid at a dose that does not affect sensory or motor functions are studied on non-associative learning abilities in the honeybee. The behavioral rpocedure is the habituation of the proboscis extension reflex (PER). Imidacloprid topically applied on the thorax (1 #mu#l) at the doses of 5, 10, and 20 ng/bee induces an increase of the gustatory threshold defined as the lowest concentration of a sucrose solution applied to the antennae able to elicit the PER. The ability of the honeybee to move in an open-field-like apparatus is impaired at the doses of 2.5, 5, 10, and 20 ng/bee. These effects are amplified with time and reach a maximum 60 min after application. The lowest dose of 1.25 mg/bee has o effect on the gustatory function but increases the motor activity and facilitates the PER habituation independently of time. This result fits our hypothesis that a slight activation of the cholinergic system with a low dose of imidacloprid can facilitate a simple form of learningin the honeybee.