Movement disorders extrapyramidal system

All About Parkinson's Disease

All About Parkinson's Disease

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NEUROPHARMACOLOGY

The observation that drugs such as reserpine and phenothiazines regularly produce extrapyramidal syndromes has clarified the neurochemical basis of movement disorders and delineated the role of neurotransmitters.

Neurotransmitter substances are synthesised and stored presynaptically. When released by an appropriate stimulus they cross the synaptic gap and combine with specific receptors of the postsynaptic cell, e.g. - acetylcholine - serotonin

- dopamine - glutamate

- y-aminobutyric acid

ACETYLCHOLINE DOPAMINE

- Synthesised by small striatal cells - Synthesised by cells of substantia

- Greatest concentration in striatum nigra (pars compacta) and nigral

- Excitatory effect. projections in striatum.

- Greatest concentration in substantia nigra.

- Inhibiting effect.

Neuromodulator substances diminish or enhancc the effects of neurotransmitters in the basal ganglia, e.g. - substance P

- encephalin

- cholecystokinin

- somatostatin.

These two transmitters

These two transmitters

Nigral Dopamine Producing

or dopamine depletion - results in the movement disorder of PARKINSONISM.

■y-Aminobutyric acid (GABA) is synthesised in the striatum and globus pallidus. It has inhibitory actions and deficiency is associated with Huntington's chorea.

Drugs may produce movement disorders by interfering with neurotransmission in the following ways:

By reducing transmitter presynaptically e.g. tetrabenazine reduces dopamine. By blocking the receptor site postsynaptically as phenothiazines do to dopamine receptors.

Both reduce effective dopamine and create a relative excess of acetylcholine

Parkinsonism

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