Over ten years ago the idea of a tripartite synapse, which suggested that synaptic transmission involved three components, a presynaptic terminal, a postsynaptic terminal and a glial cell, was put forth to the scientific community. Since then tremendous advances have been made in the field of glial biology, and it is now well- accepted that glial cells are active participants in synaptic transmission and can release chemical transmitters, in a process called gliotransmission, which can influence synaptic activity and behavior. Our lab has developed a transgenic mouse model which specifically impairs gliotransmitter release in astrocytes via the inducible expression of a dominant negative SNARE (dnSNARE) protein driven by a GFAP promoter. Using this model we have shown that gliotransmission is involved in the modulation of sleep homeostasis. More specifically, astrocytic SNARE dependent gliotransmitter release is necessary for the accumulation of sleep pressure and contributes to the impairment of working memory following sleep deprivation in an A1R dependent manner. The goal of this proposal is to further explore the role of gliotransmission in sleep homeostasis and cognition. First, we propose to determine the identity of the gliotransmitter. The effects we observe are A1R dependent which has led us to propose that astrocytic release of ATP, which is converted extracellularly to adenosine, is the putative gliotransmitter. Thus, we will directly measure extracellular adenosine levels in wild-type and dnSNARE animals during sleep deprivation. Next, we will seek to identify the activating signal for gliotransmitter release. Nitric oxide (NO) is also involved in sleep homeostasis and has been shown to increase extracellular adenosine levels, making it an intriguing potential candidate molecule for the initiation of gliotransmitter release. Thus, we will test whether NO can induce an astrocytic SNARE sensitive increase in extracellular adenosine and sleep pressure. Finally, we will assess whether the increased adenosine tone contributes to the cognitive deficits seen after sleep deprivation. The proposed experiments will take advantage of my existing skills in in vivo microdialysis and molecular biology while allowing me to gain skills in EEG/EMG recordings, electrophysiology and behavior. Sleep is important to overall health and affects all aspects of human behavior. This makes it imperative to understand the homeostatic mechanisms that underlie sleep and wakefulness and identify new regulatory targets, such as glial cells.
Sleep restriction or deprivation leads to serious cognitive and physiological consequences and many diseases and disorders are associated with disrupted sleep. This proposal will examine the homeostatic mechanisms involved in the response to disrupted sleep and identify potential new therapeutic targets.
|Blutstein, Tamara; Haydon, Philip G (2013) The Importance of astrocyte-derived purines in the modulation of sleep. Glia 61:129-39|