Addiction can primarily occur as a result of genetic vulnerability, social stress and psychological dependence. Alteration in quantities of neurochemicals present in the brain causes addiction. Neurochemicals include neurotransmitters, neuromodulators and neuropeptides. Each of these neurochemicals has distinctive regulation patterns, pathways and functions. Dopamine(3,4-dihydroxyphenethylamine) is a neurotransmitter and neuromodulator associated with Reward-motivated behaviour, present in the midbrain, VTA, cerebral cortex, hypothalamus. Pleasure and reward, movement, attention, memory are concomitants of dopamine. High levels of dopamine, achieved by psychostimulants, induce addiction. Psychostimulants act as reuptake inhibitors of dopamine, thus stagnating higher concentration in synaptic clefts. The irresistible urge is created thus.
The Adrenaline or epinephrine pump during the ‘trip’ accounts in major activation of reward pathway. It sets arise to an avalanche of events such as, elevated heart rate, vasoconstriction, and increased cardiac output. Adrenaline is more activated in the presence of a stimulant drug.
Non-adrenaline or norepinephrine is a neurotransmitter that erodes the brain of attention and responding actions. It clogs the mental ability to reason and respond.
Glutamate aids in cognitive functions such as learning and memory, but larger quantities of glutamate can affect the neurons. Primarily psychostimulants floods the brain of neurochemicals, large proportions of glutamate starts flooding the brain and damages the brain cells, thus causing brain damage or stroke.
Drugs also greatly activate Endorphin, which is a long chain of amino acid, released during exercise, excitement, pain and sexual activity. It is exponentially concerned with Euphoria.