Page "Neurotransmitter" Paragraph 28

Drugs targeting the neurotransmitter of such systems affect the whole system ; this fact explains the complexity of action of some drugs.

Cocaine, for example, blocks the reuptake of dopamine back into the presynaptic neuron, leaving the neurotransmitter molecules in the synaptic gap longer.

Since the dopamine remains in the synapse longer, the neurotransmitter continues to bind to the receptors on the postsynaptic neuron, eliciting a pleasurable emotional response.

Physical addiction to cocaine may result from prolonged exposure to excess dopamine in the synapses, which leads to the downregulation of some postsynaptic receptors.

After the effects of the drug wear off, one might feel depressed because of the decreased probability of the neurotransmitter binding to a receptor.

Prozac is a selective serotonin reuptake inhibitor ( SSRI ), which blocks re-uptake of serotonin by the presynaptic cell.

This increases the amount of serotonin present at the synapse and allows it to remain there longer, hence potentiating the effect of naturally released serotonin.

AMPT prevents the conversion of tyrosine to L-DOPA, the precursor to dopamine ; reserpine prevents dopamine storage within vesicles ; and deprenyl inhibits monoamine oxidase ( MAO )- B and thus increases dopamine levels.