SLEEP 2011 Abstract Supplement

A. Basic Science II. Cell and Molecular Biology and Genetics
0018
ACTIVATION OF THE ERK KINASE IS AN IMPORTANT
REGULATOR OF SLEEP IN DROSOPHILA MELANOGASTER
Vanderheyden WM, Shaw P
Department of Anatomy and Neurobiology, Washington University in
Saint Louis, Saint Louis, MO, USA
Introduction: Recent evidence has shown that social enrichment increases
sleep time in the fruit fly. This increase in sleep has been hypothesized
to be related to plastic changes that occur during social
enrichment. In rodents, activation of extracellular signal-regulated kinase
(ERK) has been shown to be a critical regulator of synaptic plasticity
and specifically in the synaptic changes associated with learning.
The mechanism that regulates sleep with respect to social enrichment is
poorly understood. We hypothesized that ERK may regulate sleep directly
and may be a mechanism by which plasticity alters sleep need.
Methods: Sleep and sleep homeostasis following 12 h of sleep loss was
evaluated in virgin female flies using Trikinetics monitors. Western blot
analysis was employed to determine the effects of social enrichment on
ppERK levels. Socially isolated flies (n=1) were compared to their socially
enriched siblings (n=50). Genetic analysis of ERK was accomplished
using the UAS-GAL4 system. Sleep, sleep homeostasis and the
response to social enrichment were evaluated in Gain of function alleles
(UAS-ERKact), the hypomorphic mutant for ERK, rolled (rl1), and following
pharmacological agents that inhibit ERK.
Results: Both total sleep time and sleep homeostasis are increased
when UAS-ERKact was expressed in the adult using the pan-neuronal
GeneSwitch driver Gswelav-GAL4. Conversely, mutants and pharmacological
disruption of ERK were associated with decreased baseline
sleep time and attenuated the homeostatic response. In wild-type flies,
ppERK levels were increased following social enrichment. Consistent
with these results, disrupting ERK prevents the increase in sleep typically
seen after social enrichment.
Conclusion: The mechanism by which social enrichment increases
sleep in the fruit fly is poorly understood. Our data suggest that ERK
may play a role in regulating normal sleep and may also serve as a signal
to increase sleep after social enrichment.
0019
INCREASED PRESYNAPTIC SIZE AND POSTSYNAPTIC
COMPLEXITY DURING WAKE AS COMPARED TO SLEEP IN
DROSOPHILA MELANOGASTER
Bushey DB, Tononi G, Cirelli C
Psychiatry, University of Wisconsin, Madison, WI, USA
Introduction: Molecular/electrophysiological markers of synaptic
strength are higher after wake and lower after sleep in rodents. In flies,
overall levels of synaptic proteins increase after wake and decrease
after sleep, suggesting that maintaining synaptic homeostasis may be
a conserved function of sleep. However, whether physiological sleep/
wake can drive synaptic changes within specific neural circuits remains
unknown. The synaptic homeostasis hypothesis predicts that increased
wake-related plasticity in specific neural circuits should increase their
synaptic strength and sleep need, and sleep should revert these changes,
but these predictions have not been tested.
Methods: We studied 3 neural circuits: small ventral lateral neurons
(s-LN v
s, important for arousal, circadian rhythms), mushroom bodies γ
neurons (learning/memory), and visual interneurons (VS1; orientation
during flight). Individual neurons expressing unique epitopes localized
pre- or postsynaptically were compared using confocal microscopy in
fixed brains harvested from sleeping, awake, or sleep deprived (SD) flies
(Kruskal-Wallis and Mann-Whitney tests).
Results: Synaptotagmin-eGFP labels synaptic vesicles and was used to
identify presynaptic puncta, which were larger in s-LN v
s and gamma
neurons of wake and SD flies compared to sleeping flies (P