“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

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 “http://www.rienstraclinic.com/newsletter/2006/2006Jul.html”

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

Occupy defined, non-overlapping domains Hippocampus >100,000 Synapses Bushong et al., 2002 Cortex 2-8 Somata 300-600 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; 183-92, 2002

Figure 2. One astrocyte enwraps several neuronal somata Halassa, M. M. et al. J. Neurosci. 2007;27:6473-6477 Copyright ©2007 Society for Neuroscience

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

…And Now THE PAPER

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

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

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

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

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

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”

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