Which parts of the brain secrete acetylcholine?

Brain Regions That Secrete Acetylcholine

The main brain regions that secrete acetylcholine include the basal forebrain (nucleus basalis of Meynert, diagonal band of Broca, and medial septum) and the brainstem (pedunculopontine and laterodorsal tegmental nuclei). 1, 2

Major Cholinergic Cell Groups in the Brain

Forebrain Cholinergic Nuclei

• Nucleus Basalis of Meynert (Ch4) - Provides major cholinergic innervation to the cortical mantle and amygdala 3, 2
• Diagonal Band of Broca (Ch2-Ch3) - The vertical limb (Ch2) projects to hippocampus while the horizontal limb (Ch3) provides cholinergic innervation to the olfactory bulb 2
• Medial Septum (Ch1) - Provides major cholinergic projections to the hippocampus 2

Brainstem Cholinergic Nuclei

• Pedunculopontine Tegmental Nucleus (Ch5) - Located in the pontomesencephalic reticular formation 4, 5, 2
• Laterodorsal Tegmental Nucleus (Ch6) - Located in the periventricular area 5, 2

Both Ch5 and Ch6 provide the major cholinergic innervation to the thalamus and contribute a minor component to cortical cholinergic innervation 2.

Functional Significance of Cholinergic Pathways

Sleep Regulation

• Cholinergic neurons from the pedunculopontine and lateral dorsal tegmental nuclei become more active during REM sleep 6
• Acetylcholine promotes REM sleep by inhibiting the REM-off cells in the brainstem 6

Cognitive Function

• Cholinergic neurons in the basal forebrain are severely affected in Alzheimer's disease 1
• Loss of these neurons contributes to memory and attention deficits 1
• The cholinergic system has been implicated in memory function, with age-related changes and pathological alterations potentially related to dementia 2

Motor Function

• The pedunculopontine tegmental nucleus (Ch5) innervates many nuclei of the extrapyramidal motor system 4
• Degeneration of these cholinergic neurons is observed in Parkinson's disease and progressive supranuclear palsy 4

Auditory Processing

• Cholinergic cells in the PMT innervate multiple auditory nuclei and can have widespread effects on auditory pathways 5
• These effects include plasticity, novelty detection, sensory gating, reward behavior, arousal, and attention 5

Clinical Implications

• Alzheimer's Disease: Severe loss of cholinergic neurons in the basal forebrain, particularly the nucleus basalis of Meynert, contributes to cognitive decline 1, 3
• Parkinson's Disease: Degeneration of cholinergic neurons in the pedunculopontine tegmental nucleus may contribute to motor symptoms 4
• Myasthenia Gravis: Acetylcholine receptor antibodies interfere with neuromuscular junction function, affecting extraocular muscles and causing variable strabismus and diplopia 7

Pathophysiological Relevance

In conditions like nerve agent intoxication, excessive acetylcholine accumulation at muscarinic and nicotinic receptors causes intense postsynaptic cholinergic stimulation, leading to symptoms including anxiety, disorientation, convulsions, and potentially respiratory arrest 7.

In SIDS (Sudden Infant Death Syndrome), abnormalities in the brainstem involving nicotinic acetylcholine receptors may contribute to vulnerability by altering autonomic function, arousal, and cardiovascular reflexes 7.