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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

Expression pattern of mAChR in the larval brain. Animals expressing GFP in the pattern of the mAChR-Gal4 line were mated with flies expressing GH146-QF, QUAS-Tomato. (a)–(d) are photomicrographs obtained at a magnification of 20x; ((e)–(h)) images at 40x; ((i)–(l)) at 60x. (a), (e), and (i) present DAPI fluorescence in blue; (b), (f), and (j) show red-tomato fluorescence under the expression pattern of the AL Projection Neurons; ((c), (g), and (k)) GFP expression under the control of the mAChR-Gal4; (d), (h), and (l) are overlays of the blue, red, and green images to the left. Cell bodies and processes expressing GFP under the control of mAChR expression pattern are observed in the ventral nerve cord and the MB region, particularly in the calyx region (indicated by white arrowheads) and the larval MB lobes (shown by white empty arrows). AL Projection Neurons are shown in (b), (f), (j), (h), and (l) by white arrows. Then high expression of mAChR is detected in the MB region. Microphotographs obtained from representative experiment. Scale bars indicate 50 microns.
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fig3: Expression pattern of mAChR in the larval brain. Animals expressing GFP in the pattern of the mAChR-Gal4 line were mated with flies expressing GH146-QF, QUAS-Tomato. (a)–(d) are photomicrographs obtained at a magnification of 20x; ((e)–(h)) images at 40x; ((i)–(l)) at 60x. (a), (e), and (i) present DAPI fluorescence in blue; (b), (f), and (j) show red-tomato fluorescence under the expression pattern of the AL Projection Neurons; ((c), (g), and (k)) GFP expression under the control of the mAChR-Gal4; (d), (h), and (l) are overlays of the blue, red, and green images to the left. Cell bodies and processes expressing GFP under the control of mAChR expression pattern are observed in the ventral nerve cord and the MB region, particularly in the calyx region (indicated by white arrowheads) and the larval MB lobes (shown by white empty arrows). AL Projection Neurons are shown in (b), (f), (j), (h), and (l) by white arrows. Then high expression of mAChR is detected in the MB region. Microphotographs obtained from representative experiment. Scale bars indicate 50 microns.

Mentions: First, we evaluated the expression of mAChRs in larvae. Flies expressing eGFP under the control of mAChR-Gal4 were mated with animals containing the GH146-QF, QUAS-Tomato transgenes. Thus, in these animals eGFP is expressed according to the expression pattern of the receptor, while in red it is possible to identify the AL Projection Neurons and their connection with the MB Kenyon Cells. As shown in Figure 3, mAChR is expressed at some level throughout the entire larval CNS, but it is possible to clearly observe cell bodies in the ventral nerve cord and also in the larval brain, in and surrounding the MB region. Higher magnification microphotographs show that mAChR is localized in the calyx and larval MB lobes (Figures 3(i)–3(l)). Little expression is detected in the antennal lobe. This data shows that mAChR is expressed in the larval MB.


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)

Expression pattern of mAChR in the larval brain. Animals expressing GFP in the pattern of the mAChR-Gal4 line were mated with flies expressing GH146-QF, QUAS-Tomato. (a)–(d) are photomicrographs obtained at a magnification of 20x; ((e)–(h)) images at 40x; ((i)–(l)) at 60x. (a), (e), and (i) present DAPI fluorescence in blue; (b), (f), and (j) show red-tomato fluorescence under the expression pattern of the AL Projection Neurons; ((c), (g), and (k)) GFP expression under the control of the mAChR-Gal4; (d), (h), and (l) are overlays of the blue, red, and green images to the left. Cell bodies and processes expressing GFP under the control of mAChR expression pattern are observed in the ventral nerve cord and the MB region, particularly in the calyx region (indicated by white arrowheads) and the larval MB lobes (shown by white empty arrows). AL Projection Neurons are shown in (b), (f), (j), (h), and (l) by white arrows. Then high expression of mAChR is detected in the MB region. Microphotographs obtained from representative experiment. Scale bars indicate 50 microns.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4562076&req=5

fig3: Expression pattern of mAChR in the larval brain. Animals expressing GFP in the pattern of the mAChR-Gal4 line were mated with flies expressing GH146-QF, QUAS-Tomato. (a)–(d) are photomicrographs obtained at a magnification of 20x; ((e)–(h)) images at 40x; ((i)–(l)) at 60x. (a), (e), and (i) present DAPI fluorescence in blue; (b), (f), and (j) show red-tomato fluorescence under the expression pattern of the AL Projection Neurons; ((c), (g), and (k)) GFP expression under the control of the mAChR-Gal4; (d), (h), and (l) are overlays of the blue, red, and green images to the left. Cell bodies and processes expressing GFP under the control of mAChR expression pattern are observed in the ventral nerve cord and the MB region, particularly in the calyx region (indicated by white arrowheads) and the larval MB lobes (shown by white empty arrows). AL Projection Neurons are shown in (b), (f), (j), (h), and (l) by white arrows. Then high expression of mAChR is detected in the MB region. Microphotographs obtained from representative experiment. Scale bars indicate 50 microns.
Mentions: First, we evaluated the expression of mAChRs in larvae. Flies expressing eGFP under the control of mAChR-Gal4 were mated with animals containing the GH146-QF, QUAS-Tomato transgenes. Thus, in these animals eGFP is expressed according to the expression pattern of the receptor, while in red it is possible to identify the AL Projection Neurons and their connection with the MB Kenyon Cells. As shown in Figure 3, mAChR is expressed at some level throughout the entire larval CNS, but it is possible to clearly observe cell bodies in the ventral nerve cord and also in the larval brain, in and surrounding the MB region. Higher magnification microphotographs show that mAChR is localized in the calyx and larval MB lobes (Figures 3(i)–3(l)). Little expression is detected in the antennal lobe. This data shows that mAChR is expressed in the larval MB.

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