Astrocyte-Derived Adenosine Astrocyte-Derived Adenosine and A1 Receptor Activity and A1 Receptor Activity Contribute to Sleep Loss-Contribute to Sleep Loss-

Induced Deficits in Induced Deficits in Hippocampal Synaptic Hippocampal Synaptic

Plasticity and Memory in Plasticity and Memory in Mice Mice

Mohsan Ali

BackgroundBackground• Sleep deprivation – Sleep loss

- Cognitive deficits and function

• SD increases extracellular adenosine levels in the forebrain and cortex. (Porkka-Heiskanen et al., 1997)

• Astrocytes release ATP

- ATP Adenosine

SleepSleep• Classified into rapid eye movement (REM) and

non-rapid eye movement (NREM) stages.

• REM is characterized by high frequency, low amplitude.

• NREM is characterized by low frequency, high amplitude

Sleep and MemorySleep and Memory• Synaptic scaling hypothesis suggests that net

nerve impulse increase during waking experience.(Liu et al., 2010)

• Memory trace reactivation hypothesis suggests that memory during wakefulness replays itself during sleep. (Lee and Wilson, 2002)

AstrocytesAstrocytes• Modulate synaptic activity through ATP directly

through P2 receptors.

• Controlled through increased Ca2+ concentration

• Specifically control slow oscillations during NREM

Slow OscillationSlow Oscillation• Up state – is when action potential firing occurs - Generated by synaptic inputs

• Down State – characterized by absence of synaptic inputs; membrane resting potential

• Can be generated in cortical slices

Adenosine regulationAdenosine regulation• Derived from many sources in the nervous

system

• ATP is released in the extracellular and then hydrolyzed

• Adenosine can be released through a direct pathway

AdenosineAdenosine

dnSNARE micednSNARE mice• SNARE proteins mediate exocytosis of cellular

transport vesicles.

• dnSNARE mice can not carry out exocytosis

• Astrocytic expression of dnSNARE significantly reduces extracellular adenosine.

A1R receptorA1R receptor• Adenosine binds to the A1R receptor, which

causes inhibition of synaptic transmission.

• Antagonists (CPT or DPCPX) bind to A1R receptor and enhance synaptic transmission.

• At least four different adenosine receptors: A1R, A2AR, A2BR, and A3R

Slow OscillationSlow Oscillation• During SD, sleep homeostat increases the drive

to sleep - Sleep pressure

• Sleep pressure is a measure by increased slow wave activity

• dnSNARE mice reduce the slow oscillation power

Purpose Purpose • To demonstrate that astrocyte-derived adenosine

and the adenosine receptor (A1R) play an important role in synaptic plasticity and memory deficits induced by SD.

- Whether memory in the object recognition task is

affected by SD.

Materials and Materials and MethodsMethods

• dnSNARE mice were obtained by crossing two mouse lines.

• Lights were maintained on a 12h light/dark cycle

• WT and dnSNARE confirmed by PCR

Surgical ProcedureSurgical Procedure• Brain cannula was placed at the left lateral

ventricle.

• Mini-osmotic pump was implanted between shoulder blades.

• Coronal sections stained with cresyl violet.

ElectrophysiologyElectrophysiology• Hippocampal slice preparation with ACSF

• Electrode placed at the stratum radiatum to elicit action potentials

• EPSPs recordings were made using ACSF-filled glass microelectrode

Spatial Object Spatial Object Recognition TaskRecognition Task

• Conducted in a gray rectangular box (40 X 30 X 30 cm) - polyvinyl chloride plastic

• 6 minutes – removed• After 3 min, placed in

box – two different objects for three cons. 6 minutes

• Testing session

Data analysisData analysis• ANOVA was performed on all experiments > SPSS

software - Linear regression slope

• Comparison was made using t-test

ResultsResults• dnSNARE expression: - (-Dox) dnSNARE and EGFP are coexpressed

- (+Dox) dnSNARE and EGFP are not expressed

Take Home Message…Take Home Message…• Astrocyte modulate sleep through adenosine.

• dnSNARE expressed in astrocyte reduces the power of slow oscillation.

• SD causes increase in adenosine through astrocyte

• SD impairs L-LTP in WT but not in dnSNARE.

• Astrocytes modulate synaptic activity and memory through adenosine