[Abstract Title]. - Society for Neuroscience

Title: In C57BL/6J (B6) mouse the GABAA receptor antagonist bicuculline blocks the increase
in wakefulness and decrease in sleep caused by the GABAA receptor agonist muscimol
Authors: *R. R. FLINT 1,2 , R. LYDIC 1 , H. A. BAGHDOYAN 1,2 ;
1 Dept. of Anesthesiol., 2 Dept. of Pharmacol., Univ. of Michigan, Ann Arbor, MI
Abstract: The pontine reticular formation contributes to the generation of wakefulness and rapid
eye movement sleep (REM) (Anesthesiology 103:1268, 2005). GABAergic transmission and
GABAA receptors in the pontine reticular nucleus, oral part (PnO) promote wakefulness in both
cat and rat (J Neurophysiol 82:2015, 1999; Neurosci Lett 129:95, 1991; Sleep 31:453, 2008) but
no studies have systematically examined the sleep effects of GABAergic transmission in mouse
PnO. Muscimol microinjected into the PnO of B6 mouse causes a concentration dependent
increase in wakefulness and decrease in sleep (Soc Neurosci Abstr Prog No 631.5, 2007). As a
further effort to determine whether the sleep and wake responses to PnO muscimol in B6 mouse
are mediated by GABAA receptors, the present study is testing the hypothesis that coadministration
of bicuculline with muscimol blocks the increase in wakefulness and decrease in
sleep caused by muscimol. Adult, male B6 mice (n = 3) were implanted with electrodes for
recording the electroencephalogram and electromyogram, and with a microinjection guide tube
stereotaxically aimed for the PnO. Each mouse received randomized microinjections (50 nL) of
muscimol (5.71 ng; 1 mM), muscimol and bicuculline (2.5 ng; 0.1 mM), and saline (vehicle
control) followed by a 4 h recording. States of wakefulness, non-REM sleep (NREM), and REM
were digitized and analyzed manually in 10 s bins using Icelus Data Acquisition and Analysis
software (Physiol Behav 63:67, 1998). The data were evaluated for statistical significance using
ANOVA and Tukey/Kramer multiple comparisons test. All microinjection sites were
histologically localized to the PnO. Muscimol caused a significant (p