The Journal of Neuroscience, July 1, 2002, 22(13):5597-5605
The Nitric Oxide Synthase Inhibitor
NG-Nitro-L-Arginine Increases
Basal Forebrain Acetylcholine Release during Sleep and Wakefulness
Jacqueline
Vazquez1, 2,
Ralph
Lydic1, and
Helen A.
Baghdoyan1
1 Department of Anesthesiology, University of Michigan,
Ann Arbor, Michigan 48109, and 2 Department of Neuroscience
and Anatomy, The Pennsylvania State University, Hershey, Pennsylvania
17033
Cholinergic neurotransmission in the basal forebrain changes across
the sleep/wake cycle, and considerable data show cortical activation by
ACh originating from basal forebrain neurons. These findings have
stimulated efforts to elucidate molecular modulators of ACh release
within the basal forebrain. Basal forebrain cholinergic neurons contain
nitric oxide synthase (NOS), the enzyme that produces the gaseous
neuromodulator nitric oxide. This study tested the hypothesis that
administration of an NOS inhibitor to the basal forebrain would alter
basal forebrain ACh release, sleep, and respiratory rate. Seven cats
were instrumented for recording sleep and wakefulness and for in
vivo microdialysis and microinjection. Compared with Ringer's
solution (control), microdialysis delivery of the NOS inhibitor
NG-nitro-L-arginine (NLA;
10 mM) increased ACh release during wakefulness (33%),
non-rapid eye movement (NREM) sleep (70%), and rapid eye movement
(REM) sleep (16%). Mean ± SEM ACh levels (pmol/10 min) during
control and NLA dialysis, respectively, were 0.58 ± 0.03 and
0.77 ± 0.06 in wakefulness, 0.36 ± 0.01 and 0.61 ± 0.06 in NREM sleep, and 0.68 ± 0.06 and 0.79 ± 0.09 in REM
sleep. Increases in ACh release were not evoked by dialysis delivery of
the less active enantiomer
NG-nitro-D-arginine.
Dialysis administration of NLA did not alter respiratory rate.
Sleep-dependent changes in basal forebrain ACh release were localized
specifically to lateral basal forebrain regions and did not occur in
medial basal forebrain sites. Microinjection of NLA into the lateral
basal forebrain did not significantly alter the sleep/wake cycle. In
contrast to NLA-induced depression of REM sleep and ACh release in the
cat pons, the present results demonstrate that NLA increased ACh
release in the cat basal forebrain and had no effect on sleep. The
different effects of NLA on ACh release in the cat pons and cat basal
forebrain may prove relevant for developing compounds that
differentially alter cholinergic neurotransmission in specific brain regions.
Key words:
basal forebrain; in vivo microdialysis; nitric oxide; NG-nitro-L-arginine; sleep; substantia innominata
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