1. “Astrocytic Modulation of Sleep Homeostasis and Cognitive Consequences of Sleep Loss”
Michael M. Halassa, Cedrick Florian, Tommaso Fellin, James R. Munoz, So-Young Lee, Ted Abel, Philip G. Haydon, and Marcos G. Frank
Journal Club, 10-February-2009

2. Glia Glia:Neurons = 10:1 Traditionally 3 types of Glia “Brain Glue”!?
Astrocytes
Oligodendrocytes
Microglia
Recently NG2+ Cells Added
“Brain Glue”!?
Functions
©2009 McGraw-Hill Companies, From “

3. Astrocytes!
Defined By GFAP (Glial Fibrillary Acidic Protein) Expression
Highly Ramified, Intracellular Coupling
Functions:
Metabolic Roles
K+ Buffering
Blood Brain Barrier
Precursor Cells?
©2007 The University of Utah, Genetic Science Learning Center

4. Occupy defined, non-overlapping domains
Hippocampus
>100,000 Synapses
Bushong et al., 2002
Cortex
2-8 Somata
Dendrites
Halassa et al, 2007
Bushong EA, Martone ME, Jones YZ, Ellisman MH Protoplasmic astrocytes in CA1
stratum radiatum occupy separate anatomical domains. J Neurosci 22; , 2002

5. Figure 2. One astrocyte enwraps several neuronal somata
Halassa, M. M. et al. J. Neurosci. 2007;27:
Copyright ©2007 Society for Neuroscience

6. The Tripartite Synapse
Filipodia and Lamellipodia
Envelop Synapse
Clearance of Neurotransmitters
Receptors
Calcium Transients
Gliotransmission

7. …And Now
THE PAPER

8. Outline GFAP Driven dnSNARE Assessed effects on Sleep and EEG
Attenuate exocytotic Gliotransmission
Assessed effects on Sleep and EEG
Pharmacological experiments to characterise cause of these effects
Object recognition task to examine effects on sleep deprivation induced memory impairments

9. dnSNARE Tetracycline Transactivator (tTA) under GFAP promoter
dnSNARE under tet.O promoter
tTA activates tet.O and drives expression of dnSNARE
Conditional supression:
Doxycycline in the diet
<50% cortical astrocytes express transgene

10. No significant alterations to total sleep time, REM time, NREM time, or 24-hour EEG spectra between groups
Open Circles/Bars: Wild Type
Closed Circles/Bars: dnSNARE

12. During the Light Phase…
(C-G, After 6-Hour Sleep Deprivation Protocol)

13. Mechanism assumed to be inhibition of extracellular adenosine build-up, acting via A1R
Tests:
Occlusion: (G)
Mimic: (H) and (I)

14. Effects of Sleep Deprivation on Memory
Sleep deprivation, linked to impaired memory and cognitive function
Novel Object Recognition task sensitive to the effects of “sleep pressure”

15. Not an Effect of Sleep, rather Sleep Pressure/Adenosine
dnSNARE/A1R antagonism protects against Sleep deprivation induced impairments
dnSNARE Rats
No difference in exploration time
No differences in Anxiety
No Motor impairment
No contextual fear conditioning impairments
Not an Effect of Sleep, rather Sleep Pressure/Adenosine