Abstract
The most studied form of associative learning in Drosophila consists in pairing an odorant, the conditioned stimulus (CS), with an unconditioned stimulus (US). The timely arrival of the CS and US information to a specific Drosophila brain association region, the mushroom bodies (MB), can induce new olfactory memories. Thus, the MB is considered a coincidence detector. It has been shown that olfactory information is conveyed to the MB through cholinergic inputs that activate acetylcholine (ACh) receptors, while the US is encoded by biogenic amine (BA) systems. In recent years, we have advanced our understanding on the specific neural BA pathways and receptors involved in olfactory learning and memory. However, little information exists on the contribution of cholinergic receptors to this process. Here we evaluate for the first time the proposition that, as in mammals, muscarinic ACh receptors (mAChRs) contribute to memory formation in Drosophila. Our results show that pharmacological and genetic blockade of mAChRs in MB disrupts olfactory aversive memory in larvae. This effect is not explained by an alteration in the ability of animals to respond to odorants or to execute motor programs. These results show that mAChRs in MB contribute to generating olfactory memories in Drosophila.
Highlights
Different training protocols used in Drosophila have helped us advance our understanding on the cellular and genetic basis for learning and memory
These data were obtained modifying only the dilution of EA while AA was used at a 1 : 10 dilution and reflects how important it is to control for the naıve response of larvae to odorants, as to find dilutions that lead to an equal distribution of animals when in presence of the two odorants
Some of the key contributors to learning and memory are highly conserved from arthropods to mammals
Summary
Different training protocols used in Drosophila have helped us advance our understanding on the cellular and genetic basis for learning and memory. One of the most studied and best understood is the associative learning of odors, where an odorant that has or does not has an intrinsic value for the animal (the CS) is paired with the US. It has been accepted that the timely, coincident arrival of the information of the CS and the US to MB KCs is essential to generate new olfactory memories [3,4,5,6]. This is valid for adult flies and in animals at the larval stage, as shown previously [7, 8]
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