Adrenergic and Cholinergic Modulation of Spontaneous and Brain Stem Reticular Formation Stimulation Induced Desynchronization of the Cortical EEG in Freely Moving Behaving Cats

Volume 1, Number 1, Year 1999

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 �g/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