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Neocortical activation: modulation by multiple pathways acting on central cholinergic and serotonergic systems
H C Dringenberg1, C H Vanderwolf
1Neuroscience Program, University of Western Ontario, London, Canada. dringenb@uni-duesseldorf.de
Experimental Brain Research
|August 1, 1997
Summary
This study reveals that brain stimulation can induce cortical activation via cholinergic and serotonergic pathways. These systems modulate neuronal activity in the basal forebrain, influencing brain states like large irregular slow activity and low voltage fast activity.
Area of Science:
- Neuroscience
- Neurophysiology
- Brain Stimulation
Background:
- Electrocorticographic (ECoG) activation, characterized by low voltage fast activity (LVFA), is crucial for cognitive functions.
- Forebrain and midbrain structures are known to mediate cerebral activation.
- The neurochemical underpinnings of ECoG activation, particularly the roles of acetylcholine and serotonin, require further elucidation.
Purpose of the Study:
- To investigate the central systems mediating electrocorticographic activation induced by electrical stimulation of forebrain and midbrain areas.
- To differentiate the neurochemical pathways (cholinergic vs. serotonergic) responsible for ECoG activation.
- To examine the influence of these activating systems on basal forebrain neuronal activity.
Main Methods:
- Experiments were conducted on urethane-anesthetized rats.
- Electrical stimulation was applied to various brain regions, including the amygdala, dorsal raphe, locus coeruleus, superior colliculus, and orbitofrontal cortex.
- Pharmacological agents, including scopolamine, atropine, methiothepin, and ketanserin, were administered to probe neurochemical mechanisms.
- Electrocorticographic activity and extracellular neuronal firing rates in the basal forebrain were recorded.
Main Results:
- Electrical stimulation of the amygdala, dorsal raphe, locus coeruleus, and superior colliculus induced LVFA, suppressing large irregular slow activity (LISA).
- Amygdala and locus coeruleus-induced LVFA were sensitive to anti-muscarinic agents (scopolamine, atropine), suggesting cholinergic involvement.
- Superior colliculus-induced LVFA was resistant to atropine but sensitive to serotonergic antagonists (methiothepin, ketanserin).
- Orbitofrontal cortex stimulation produced atropine-sensitive LVFA, further enhanced by methiothepin.
- Single-pulse stimulation of amygdala and locus coeruleus excited basal forebrain neurons more active during LVFA and inhibited those more active during LISA.
Conclusions:
- Widely distributed neuronal systems can induce electrocorticographic activation through cholinergic and/or serotonergic mechanisms.
- Cholinergic pathways, potentially originating from the basal forebrain, contribute to atropine-sensitive LVFA.
- Serotonergic pathways are involved in LVFA induced by superior colliculus stimulation.
- These activating systems modulate basal forebrain neuronal activity, influencing the balance between cortical activation and suppression.