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Muscarinic ACh Receptors Contribute to Aversive Olfactory Learning in Drosophila.

Silva B, Molina-Fernández C, Ugalde MB, Tognarelli EI, Angel C, Campusano JM - Neural Plast. (2015)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Laboratorio Neurogenética de la Conducta, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Alameda 340, 8331150 Santiago, Chile.

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.

No MeSH data available.


Related in: MedlinePlus

Schematic of the protocol used for generating aversive olfactory memories in Drosophila larvae. Training and memory tests are carried out in square shape Petri dishes that in opposite sides have containers where odorants are located (represented in yellow) (a) Training: fifteen or more larvae are exposed for 3 min to only one odorant in a dish half-covered with agar supplemented with 2 M NaCl (Odor A + salt). Then animals are exposed to a second odorant in a different Petri plate half-covered with regular agar. This is one training cycle. This procedure is repeated two more times. Afterwards, memory test is carried out. (b) Memory test: to evaluate aversive olfactory memory, animals are placed in the centerline of a square plate, so they are equally exposed to the two odorants, each one in opposite containers. After three minutes, the number of larvae at both sides of the center area is counted.
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fig1: Schematic of the protocol used for generating aversive olfactory memories in Drosophila larvae. Training and memory tests are carried out in square shape Petri dishes that in opposite sides have containers where odorants are located (represented in yellow) (a) Training: fifteen or more larvae are exposed for 3 min to only one odorant in a dish half-covered with agar supplemented with 2 M NaCl (Odor A + salt). Then animals are exposed to a second odorant in a different Petri plate half-covered with regular agar. This is one training cycle. This procedure is repeated two more times. Afterwards, memory test is carried out. (b) Memory test: to evaluate aversive olfactory memory, animals are placed in the centerline of a square plate, so they are equally exposed to the two odorants, each one in opposite containers. After three minutes, the number of larvae at both sides of the center area is counted.

Mentions: A new protocol to generate olfactory aversive memories based on the protocol discussed in Gerber at al., 2010 [26], was used in our experiments. The main difference is that training and test plates were 100 mm noncompartmentalized square-shape Petri dishes (Sterilin, UK). Containers for odorants were placed at opposite sides of the plate. The general arrangement is shown in Figure 1. Square-shaped plates were half-covered with solidified agar (1%), which was supplemented or not with 2 M NaCl (the US). All procedures (training, memory assessment, and olfactory discrimination assays) were carried out in plates covered by a lid, which was perforated in the center (0.5 mm diameter holes) for good aeration.


Muscarinic ACh Receptors Contribute to Aversive Olfactory Learning in Drosophila.

Silva B, Molina-Fernández C, Ugalde MB, Tognarelli EI, Angel C, Campusano JM - Neural Plast. (2015)

Schematic of the protocol used for generating aversive olfactory memories in Drosophila larvae. Training and memory tests are carried out in square shape Petri dishes that in opposite sides have containers where odorants are located (represented in yellow) (a) Training: fifteen or more larvae are exposed for 3 min to only one odorant in a dish half-covered with agar supplemented with 2 M NaCl (Odor A + salt). Then animals are exposed to a second odorant in a different Petri plate half-covered with regular agar. This is one training cycle. This procedure is repeated two more times. Afterwards, memory test is carried out. (b) Memory test: to evaluate aversive olfactory memory, animals are placed in the centerline of a square plate, so they are equally exposed to the two odorants, each one in opposite containers. After three minutes, the number of larvae at both sides of the center area is counted.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4562076&req=5

fig1: Schematic of the protocol used for generating aversive olfactory memories in Drosophila larvae. Training and memory tests are carried out in square shape Petri dishes that in opposite sides have containers where odorants are located (represented in yellow) (a) Training: fifteen or more larvae are exposed for 3 min to only one odorant in a dish half-covered with agar supplemented with 2 M NaCl (Odor A + salt). Then animals are exposed to a second odorant in a different Petri plate half-covered with regular agar. This is one training cycle. This procedure is repeated two more times. Afterwards, memory test is carried out. (b) Memory test: to evaluate aversive olfactory memory, animals are placed in the centerline of a square plate, so they are equally exposed to the two odorants, each one in opposite containers. After three minutes, the number of larvae at both sides of the center area is counted.
Mentions: A new protocol to generate olfactory aversive memories based on the protocol discussed in Gerber at al., 2010 [26], was used in our experiments. The main difference is that training and test plates were 100 mm noncompartmentalized square-shape Petri dishes (Sterilin, UK). Containers for odorants were placed at opposite sides of the plate. The general arrangement is shown in Figure 1. Square-shaped plates were half-covered with solidified agar (1%), which was supplemented or not with 2 M NaCl (the US). All procedures (training, memory assessment, and olfactory discrimination assays) were carried out in plates covered by a lid, which was perforated in the center (0.5 mm diameter holes) for good aeration.

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Laboratorio Neurogenética de la Conducta, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Alameda 340, 8331150 Santiago, Chile.

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.

No MeSH data available.


Related in: MedlinePlus