Imbalances in the reward system can come up through different reasons
1.if the person inherited genetically neurotransmitter deficits:
2.dysfunctional neurochemicals that creates stress:
3.alteration in drug abuse:
4.a nutritional imbalance:

When the Normal Reward System gets introduced to Cocaine then the acute response is.
1.The recycling of serotonin and dopamine is inhibited so that they have a prolonged affect at the synapses.
2. The transmission of the dopamine, nor epinephrine, and serotonin gets increased, so as a result it increases supply to the synapses.

The net effect is that it creates an oversupply or it floods the synapses with more neurotransmitters, that creates a euphoric state.

The Chronic response would be:

1.Depletion of Neurotransmitters
2.With the continuous use of Cocaine molecules it further interferes the release of the neurotransmitters and blocks the receptor site in the reward area.
3.At the same time the number of receptor sites increases, resulting an even greater discrepancy between the amount of transmitters that are available and the number of receptor sites occupied.
4.There is a stronger need of Cocaine in order to obtain a High.
5.The craving remains at a very high level, and the User experiences a feeling of unhappiness and depression.
6. these symptoms become more severe, and the user experiences a “CRASH”