Question

what are the consequences of decreased dopaminergic tone in the striatum on the excitation status (eg. increased or decreased inhibition) of the projection neurons that arise from the subthalamic nucleus and Substantia Nigra and how does dopaminergic receptor agonists and antagonist treatment affect those neurons?

Answer 1

Dopamine are synthesized from the amino acid tryosine..They are excitatory at some synapses and inhibitory at others.Caffeine ,benezedrine and nicotine reduce the threshold for excitation of neurons and result in fascilitation.Hypnotics ,transquilers and anaesthetics depresss impulse conduction and synaptic transmission by increasing threshold for excitation of neurons.There are several ways to modify chemical synaptic transmission such as stimulate neurotransmitter release,block or enhance neurotransmitter release An agent that enhances synaptic transmission or mimics the effect of a natural neurotransmitter is an agnosit,whereas one that blocks the action of a neurotransmitter is an antagonist.

Substances that are antagnoist or agonosit have great potential for benefit or harm.The plant derivative curare( drugs) blocks acetylcholine receptors and thus can cause muscle paralysis.These drugs are often used in surgery for relax skeletal mscles.