Cocaine & It's Affect On The Brain
Cocaine acts by blocking the reuptake of certain neurotransmitters such as dopamine, norepinephrine, and serotonin.
By binding to the transporters that normally remove the excess of these neurotransmitters from the synaptic gap, cocaine prevents
them from being reabsorbed by the neurons that released them and thus increases their concentration in the synapses (see animation).
As a result, the natural effect of dopamine on the post-synaptic neurons is amplified. The group of neurons thus modified
produces the euphoria (from dopamine), feelings of confidence (from serotonin), and energy (from norepinephrine) typically
experienced by people who take cocaine.
In addition, because the norepinephrine neurons in the locus coeruleus project their axons into all the main
structures of the forebrain, the powerful overall effect of cocaine can be readily understood.
In chronic cocaine consumers, the brain comes to rely on this exogenous drug to maintain the high degree of pleasure
associated with the artificially elevated dopamine levels in its reward circuits. The postsynaptic membrane can even adapt
so much to these high dopamine levels that it actually manufactures new receptors. The resulting increased sensitivity produces
depression and cravings if cocaine consumption ceases and dopamine levels return to normal.
Dependency on cocaine is thus closely related to its effect on the neurons of the reward circuit.
Ecstasy
Ecstasy (MDMA) is a synthetic drug. It acts simultaneously as a stimulant and a hallucinogen because of its molecular
structure, which is similar to that of both amphetamines and LSD. Like amphetamines and cocaine, ecstasy blocks the reuptake
pumps for certain neurotransmitters, thus increasing their levels in the synaptic gap and their effect on the post-synaptic
neurons’ receptors.
While ecstasy also potentiates the effects of norepinephrine and dopamine, it is distinguished from other psychostimulants
by its strong affinity for serotonin transporters. The initial effect of ecstasy is thus an increased release of serotonin
by the serotonergic neurons. The individual may then experience increased energy, euphoria, and the suppression of certain
inhibitions in relating to other people.
A few hours later, there is a decrease in serotonin levels, amplified by the reduced activity of tryptophane
hydroxylase, the enzyme responsible for synthesizing serotonin. This decrease can last much longer than the initial increase.
Once again, an artificial increase in the level of a neurotransmitter exercises negative feedback on the enzyme that manufactures
it. As a result, when intake of the drug ceases, the excess turns into a shortage.
Like all psychoactive drugs that produce a sensation of pleasure, ecstasy also increases the release of dopamine
into the reward circuit. In addition, the extra serotonin produced by ecstasy leads indirectly to excitement of the dopaminergic
neurons by the serotonergic neurons that connect to them.
The toxicity of ecstasy for humans has not been clearly established, but animal studies have shown that chronic
high doses of MDMA lead to selective destruction of the terminal buttons of the serotonergic neurons.
These are just some of the drugs and their frightning affects on the BRAIN! :)
