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Old 05-01-2010
anoop_1198 anoop_1198 is offline
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Yup's the explanation -
The correct answer is D. Methamphetamine (and amphetamine) acts by gaining entrance to dopamine and norepinephrine (and serotonin) nerve terminals, causing the release of these neurotransmitters via the uptake carriers. Dopamine is believed to play an important role in the reward system of the brain, and is thought to be a significant factor in the reinforcing effects of stimulants. One area of the brain that is thought to be involved in this reward system is the dopaminergic projection from the ventral tegmental area of the midbrain to the nucleus accumbens of the forebrain.

Although methamphetamine is a weak inhibitor of monoamine oxidase (MAO), and would therefore weakly block the metabolism of catecholamines (choice A), this is not the primary mechanism of action of this drug.

Methamphetamine acts as an indirect-acting agonist, via the release of neurotransmitter, not as a direct agonist (choices B and C).

Methamphetamine does induce norepinephrine release (choice E), but this plays a role in the production of systemic side effects (e.g., hypertension), rather than in the central effect of reinforcement.
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