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

I t is almost half a century that Moruzzi and Magoun (1), through their epoch making study, showed that the brain stem reticular formation (BSRF) is primarily responsible for cortical EEG desynchronization (DSYN). While the overall concept still holds good, the role played by different BSRF neurons and respective neurotransmitters for modulation of EEG continues to be under intense investigation. Stimulation of both adrenergic (2) and cholinergic (3) neuron rich areas in the brain are known to induce EEG DSYN. Local and systemic injections of noradrenergic and cholinergic agonist (2,4-6) have been reported to induce DSYN while their antagonist (5,7) induced synchronization (SYN) of the cortical EEG. Level of acetylcholine (ACh) was found to increase in the cortex during DSYN (8). However, the norepinephrine(NE)-ergic neurons are active during non-REM sleep state and cease firing during REM sleep although the EEG remains desynchronized during both the states. Similarly, there are certain group of cholinergic neurons which are active during REM sleep (9). Thus, it is likely that the adrenergic and the cholinergic systems have different roles to play in DSYN of the cortical EEG. Recently Adrenergic and Cholinergic Modulation of Spontaneous and Brain Stem Reticular Formation Stimulation Induced Desynchronization of the Cortical EEG in Freely Moving Behaving Cats