A NEW ATTEMPT TO ASSESS THE EFFECT OF LEARNING-PROCESSES ON THE CHOLINERGIC SYSTEM - STUDIES ON FRUIT-FLIES AND HONEYBEES

The effect of training on the functioning of the cholinergic system wa s investigated in fruitflies and in honeybees. Drosophila were submitt ed to a passive avoidance conditioning of the proboscis extension resp onse (PER). Flies had to learn to suppress the sugar-induced PER to av oid an aversive quinine reinforcement. In a yoked control group, the p unishment was administered with no relation to the response displayed. Honeybees underwent a five trial olfactory conditioning of the PER el icited by an antennal gustatory stimulation. In the control group, olf actory and gustatory stimulations were unpaired to prevent a learning process from developing. Immediately at the end of the learning sessio n, acetylcholinesterase (AChE) activity was individually measured on t he whole animal for Drosophila and on the head for the honeybee in exp erimental and in control groups. In fruitflies and honeybees, the ACHE rate did not differ between the experimental group and its respective control group. Moreover, no significant correlation could be found in dividually between the learning performance and the ACHE rate in eithe r Drosophila or in honeybees. This experiment did not reveal any modul atory effect of the learning acquisition level on the AChE activity in insects as was previously reported in honeybees (11). (C) 1998 Elsevi er Science Inc.