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A single pair of neurons links sleep to memory consolidation in Drosophila melanogaster.

Haynes PR, Christmann BL, Griffith LC - Elife (2015)

Bottom Line: Downregulation of α'/β' GABAA and GABABR3 receptors results in sleep loss, suggesting these receptors are the sleep-relevant targets of DPM-mediated inhibition.Regulation of sleep by neurons necessary for consolidation suggests that these brain processes may be functionally interrelated via their shared anatomy.These findings have important implications for the mechanistic relationship between sleep and memory consolidation, arguing for a significant role of inhibitory neurotransmission in regulating these processes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Volen Center for Complex Systems, National Center for Behavioral Genomics, Brandeis University, Waltham, United States.

ABSTRACT
Sleep promotes memory consolidation in humans and many other species, but the physiological and anatomical relationships between sleep and memory remain unclear. Here, we show the dorsal paired medial (DPM) neurons, which are required for memory consolidation in Drosophila, are sleep-promoting inhibitory neurons. DPMs increase sleep via release of GABA onto wake-promoting mushroom body (MB) α'/β' neurons. Functional imaging demonstrates that DPM activation evokes robust increases in chloride in MB neurons, but is unable to cause detectable increases in calcium or cAMP. Downregulation of α'/β' GABAA and GABABR3 receptors results in sleep loss, suggesting these receptors are the sleep-relevant targets of DPM-mediated inhibition. Regulation of sleep by neurons necessary for consolidation suggests that these brain processes may be functionally interrelated via their shared anatomy. These findings have important implications for the mechanistic relationship between sleep and memory consolidation, arguing for a significant role of inhibitory neurotransmission in regulating these processes.

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DPMs are serotonergic, but not dopaminergic.(A–B) Top: VT64246-GAL4 was used to drive expression of membrane-localized mCD8-GFP in DPM cell bodies, which was visualized with an anti-GFP antibody. Middle: Brains were stained with antibodies against (A) 5-HT (N = 6/6 cell bodies with positive staining) and (B) TH (N = 6/6 cell bodies with no staining). Although some TH-positive neurites from other neurons cross over the location of the DPM cell bodies resulting in very localized correlation between channels (* in image), the DPMs do not show a general colocalization with anti-TH. Bottom: ICA was used to visualize the relative colocalization between DPM > GFP and transmitter staining in pairs of DPMs. For ICA, orange indicates colocalization/correlation of pixel intensities between channels and purple indicates a lack of colocalization/anticorrelation of pixel intensities between channels relative to the scale shown for each image (see ‘Materials and methods’ for further details).DOI:http://dx.doi.org/10.7554/eLife.03868.011
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fig3s1: DPMs are serotonergic, but not dopaminergic.(A–B) Top: VT64246-GAL4 was used to drive expression of membrane-localized mCD8-GFP in DPM cell bodies, which was visualized with an anti-GFP antibody. Middle: Brains were stained with antibodies against (A) 5-HT (N = 6/6 cell bodies with positive staining) and (B) TH (N = 6/6 cell bodies with no staining). Although some TH-positive neurites from other neurons cross over the location of the DPM cell bodies resulting in very localized correlation between channels (* in image), the DPMs do not show a general colocalization with anti-TH. Bottom: ICA was used to visualize the relative colocalization between DPM > GFP and transmitter staining in pairs of DPMs. For ICA, orange indicates colocalization/correlation of pixel intensities between channels and purple indicates a lack of colocalization/anticorrelation of pixel intensities between channels relative to the scale shown for each image (see ‘Materials and methods’ for further details).DOI:http://dx.doi.org/10.7554/eLife.03868.011

Mentions: The shared requirement for activity during memory consolidation (Krashes et al., 2007; Krashes and Waddell, 2008) as well as the extensive physical connectivity as determined by membrane-localized GRASP (Pitman et al., 2011) strongly suggests that DPM and MB neurons are synaptically connected. Given the lack of information on the functional nature of the connections, we set out as a first step to determine what neurotransmitters are present in DPM neurons. Colocalization of mCD8-GFP expression in DPM cell bodies with staining against a panel of neurotransmitters shows that DPM neurons contain both GABA (Figure 3A) and 5HT (Figure 3—figure supplement 1A). DPM cell bodies also stain positively for Gad1 (Figure 3C), the GABA synthetic enzyme. We found no evidence for expression of ChAT, the ACh synthetic enzyme (Figure 3C), or tyrosine hydroxylase (TH), the rate-limiting enzyme for catecholamine synthesis (Figure 3—figure supplement 1B). These combined results suggest that the DPM neurons release GABA and 5HT, but not ACh or dopamine.10.7554/eLife.03868.010Figure 3.DPMs are GABAergic, but not cholinergic.


A single pair of neurons links sleep to memory consolidation in Drosophila melanogaster.

Haynes PR, Christmann BL, Griffith LC - Elife (2015)

DPMs are serotonergic, but not dopaminergic.(A–B) Top: VT64246-GAL4 was used to drive expression of membrane-localized mCD8-GFP in DPM cell bodies, which was visualized with an anti-GFP antibody. Middle: Brains were stained with antibodies against (A) 5-HT (N = 6/6 cell bodies with positive staining) and (B) TH (N = 6/6 cell bodies with no staining). Although some TH-positive neurites from other neurons cross over the location of the DPM cell bodies resulting in very localized correlation between channels (* in image), the DPMs do not show a general colocalization with anti-TH. Bottom: ICA was used to visualize the relative colocalization between DPM > GFP and transmitter staining in pairs of DPMs. For ICA, orange indicates colocalization/correlation of pixel intensities between channels and purple indicates a lack of colocalization/anticorrelation of pixel intensities between channels relative to the scale shown for each image (see ‘Materials and methods’ for further details).DOI:http://dx.doi.org/10.7554/eLife.03868.011
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4305081&req=5

fig3s1: DPMs are serotonergic, but not dopaminergic.(A–B) Top: VT64246-GAL4 was used to drive expression of membrane-localized mCD8-GFP in DPM cell bodies, which was visualized with an anti-GFP antibody. Middle: Brains were stained with antibodies against (A) 5-HT (N = 6/6 cell bodies with positive staining) and (B) TH (N = 6/6 cell bodies with no staining). Although some TH-positive neurites from other neurons cross over the location of the DPM cell bodies resulting in very localized correlation between channels (* in image), the DPMs do not show a general colocalization with anti-TH. Bottom: ICA was used to visualize the relative colocalization between DPM > GFP and transmitter staining in pairs of DPMs. For ICA, orange indicates colocalization/correlation of pixel intensities between channels and purple indicates a lack of colocalization/anticorrelation of pixel intensities between channels relative to the scale shown for each image (see ‘Materials and methods’ for further details).DOI:http://dx.doi.org/10.7554/eLife.03868.011
Mentions: The shared requirement for activity during memory consolidation (Krashes et al., 2007; Krashes and Waddell, 2008) as well as the extensive physical connectivity as determined by membrane-localized GRASP (Pitman et al., 2011) strongly suggests that DPM and MB neurons are synaptically connected. Given the lack of information on the functional nature of the connections, we set out as a first step to determine what neurotransmitters are present in DPM neurons. Colocalization of mCD8-GFP expression in DPM cell bodies with staining against a panel of neurotransmitters shows that DPM neurons contain both GABA (Figure 3A) and 5HT (Figure 3—figure supplement 1A). DPM cell bodies also stain positively for Gad1 (Figure 3C), the GABA synthetic enzyme. We found no evidence for expression of ChAT, the ACh synthetic enzyme (Figure 3C), or tyrosine hydroxylase (TH), the rate-limiting enzyme for catecholamine synthesis (Figure 3—figure supplement 1B). These combined results suggest that the DPM neurons release GABA and 5HT, but not ACh or dopamine.10.7554/eLife.03868.010Figure 3.DPMs are GABAergic, but not cholinergic.

Bottom Line: Downregulation of α'/β' GABAA and GABABR3 receptors results in sleep loss, suggesting these receptors are the sleep-relevant targets of DPM-mediated inhibition.Regulation of sleep by neurons necessary for consolidation suggests that these brain processes may be functionally interrelated via their shared anatomy.These findings have important implications for the mechanistic relationship between sleep and memory consolidation, arguing for a significant role of inhibitory neurotransmission in regulating these processes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Volen Center for Complex Systems, National Center for Behavioral Genomics, Brandeis University, Waltham, United States.

ABSTRACT
Sleep promotes memory consolidation in humans and many other species, but the physiological and anatomical relationships between sleep and memory remain unclear. Here, we show the dorsal paired medial (DPM) neurons, which are required for memory consolidation in Drosophila, are sleep-promoting inhibitory neurons. DPMs increase sleep via release of GABA onto wake-promoting mushroom body (MB) α'/β' neurons. Functional imaging demonstrates that DPM activation evokes robust increases in chloride in MB neurons, but is unable to cause detectable increases in calcium or cAMP. Downregulation of α'/β' GABAA and GABABR3 receptors results in sleep loss, suggesting these receptors are the sleep-relevant targets of DPM-mediated inhibition. Regulation of sleep by neurons necessary for consolidation suggests that these brain processes may be functionally interrelated via their shared anatomy. These findings have important implications for the mechanistic relationship between sleep and memory consolidation, arguing for a significant role of inhibitory neurotransmission in regulating these processes.

Show MeSH
Related in: MedlinePlus