Hypothalamic Neuronal Activity During Insomnia Induced by Chronic Ethanol Exposure

Severe insomnia occurs during the withdrawal from chronic use of alcohol. To gain relief from
insomnia, alcoholics begin drinking again. Although the cause of the insomnia is unknown, indirect
measurements of neuronal activity (c-FOS, fMRI) suggest that during insomnia, more of the arousal-
promoting neurons are hyperactive. The status of the sleep-promoting neurons is unknown but are likely to be
less active. Our overall hypothesis is that it is the imbalance in activity between wake versus sleep-promoting
neurons that is the basis of insomnia during the withdrawal from alcohol. We will directly test this hypothesis
in a proven mouse model of chronic ethanol intoxication using newly developed neuroscience tools. Aim 1 will
use a miniscope to image Ca2+ influx (as a readout of cell activity) in specific hypothalamic wake-promoting
(orexin) or hypothalamic sleep-promoting (GABA) neurons before, during and after chronic intermittent
exposure to alcohol (CIE). We will image the neurons during waking, NREM, and REM sleep. We hypothesize
that during the CIE-period of insomnia, the orexin neurons are more active while the sleep-promoting GABA
neurons are less active. We have robust preliminary data indicating that the GABA neurons have become less
active after chronic alcohol exposure. Similarly, our preliminary data reveals that orexin neurons have become
more active. The deep-brain Ca2+ imaging method provides descriptive data. Thus Aims 2 and 3 will use
pharmacogenetics to mechanistically test the hypothesis that CIE has shifted the excitability thresholds of the
GABA and orexin neurons. In-vitro slice electrophysiology studies will confirm the hypothesis. To induce sleep
to correct the insomnia, Aim 2 will activate the GABA neurons, while Aim 3 will inhibit the orexin neurons.
Aim 4 will test the hypothesis that after CIE, because sleep has improved with our pharmacogenetic
manipulations, then the mice will show less preference for drinking alcohol. This aim goes to the core of our
hypothesis that improving sleep prevents alcohol relapse.
The overall impact of our studies is that, for the first time, hard evidence will mechanistically link insomnia
during the withdrawal from chronic ethanol intoxication to changes of activity in specific phenotypes of
hypothalamic sleep or wake-promoting neurons. Furthermore, our aims are translational and will aid in the
development of appropriate treatments for insomnia. Our aims are integrated and employ cutting-edge tools to
understand how chronic ethanol exposure disrupts sleep homeostasis. This project will be conducted jointly by
experts in the areas of sleep neurobiology and alcohol addiction.

Grant Number: 5R01AA029129-04
NIH Institute/Center: NIH
Principal Investigator: Carlos Blanco-Centurion