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Adrenergic and Cholinergic Modulation of
Spontaneous and Brain Stem Reticular
Formation Stimulation Induced
Desynchronization of the Cortical EEG in
Freely Moving Behaving Cats
Stephen Thankachan, Ph.D., Fakhrul Islam, Ph.D.,
and Birendra N.Mallick, Ph.D.
The brain stem reticular formation is responsible for EEG desynchronization.It bears,among
others,adrenergic and cholinergic neurons.Neurons of this area project directly or indirectly
to the cortex.Isolated studies have shown that both the adrenergic as well as the cholinergic
inputs may induce and modulate cortical EEG desynchronization,however,their relative role
was unknown.In this study,the differential influence of adrenergic and cholinergic inputs in
cortical EEG desynchronization during spontaneous and brain stem reticular formation
stimulation induced wakefulness was investigated in freely moving chronically prepared
cats.The cats were chronically prepared for standard electrophysiologcial sleep-
wakefulness recording and also with stimulating electrode in the midbrain reticular formation.
After recovery,baseline recording of sleep-wakefulness was done.Thereafter,either
adrenergic . 1-adrenoceptor antagonist,prazosin (1 mg/Kg),. 2-adrenoceptor agonist,
clonidine (25 µg/Kg),. 2-adrenoceptor antagonist,yohimbine (1 mg/Kg),. -adrenoceptor
antagonist,propranolol (10 mg/kg)or,cholinergic muscarinic receptor antagonist,
scopolamine (0.5 mg/Kg)was injected i.p.and the effect on spontaneous as well as
midbrain reticular formation stimulation induced EEG desynchronization investigated.It was
found that desynchronization of the EEG was modulated significantly by both,the cholinergic
as well as by the adrenergic systems.The cholinergic action was mediated through the
muscarinic receptor while the adrenergic through the . 1-adrenoceptor.The effect of the
former was relatively long lasting and it reduced the high frequency waves while the latter
was more effective in increasing the rhythmicity of the EEG waves in the power spectrum
record.These differences possibly have relevance in EEG desynchronization during
wakefulness and REM sleep.(Sleep and Hypnosis 1999;1:14-21)
| Keywords: adrenergic, agonist, antagonist, brain stem reticular formation, cholinergic, EEG |
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