The effects of atropine on brain

 

The effects of atropine on brain

The evolution of the finest brain on the planet must have taken millions of years to reach its present complexity.

The brain functions as a single unit but is made up of closely knit “discrete” structures communicating with each other with mindboggling agility.

The “discrete” structures  are nothing but the cerebrum, cerebellum, brainstem, basal ganglia and others.

The neural processing within the “discrete” structures and the communication of neural information between them, are both dependent on neurotransmitters.

The balance between the two ubiquitous neurotransmitters- acetylcholine and dopamine is of paramount importance in maintaining CNS physiology.

Atropine, a non-selective muscarinic blocker (read acetylcholine receptor blocker) crosses the blood brain barrier and therefore, has widespread CNS effects.

Part of the brain	Effect of atropine	Possible explanation
Cerebral cortex	Cognitive impairment manifested as memory loss, inability to perform skilful mental tasks, indecision etc	Projections to the cerebrum from other parts of the brain and the inter-neuronal communication within the cerebrum for cognitive processing are mediated by acetylcholine. Atropine blocks the muscarinic receptors (M1)  in the CNS and therefore causes cognitive impairment.
Basal ganglia	Motor hyperactivity	Tone and movement of muscles depends on the delicate balance between acetylcholine and dopamine in the striatum. Atropine, by blocking acetylcholine action, promotes the unimpeded action of dopamine in the striatum, resulting in hyperkinesia and motor incoordination.
Mesolimbic pathway	Disorientation, hallucination, confusion, excitement	Tilting of balance towards dopaminergic transmission because of cholinergic blockade. Dopamine excess in the striatum has been shown to cause psychotic behaviour.
Vestibular Nuclei	Loss of balance and equilibrium at very high doses	Suppression of cholinergic transmission in the vestibular apparatus in inner ear. This action has therapeutic use in motion sickness.