Which of the following statements correctly describes the physiological mechanism of action of cocaine?

• A. Cocaine stimulates the release of gamma-aminobutyric acid (GABA) from presynaptic terminals.
• B. Cocaine acts as a direct agonist at muscarinic acetylcholine receptors.
• C. Cocaine blocks the reuptake of dopamine in the synaptic cleft, increasing dopamine levels in the brain.
• D. Cocaine inhibits the synthesis of serotonin in presynaptic neurons.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the physiological mechanism of action of cocaine. Cocaine primarily affects the central nervous system by altering neurotransmitter activity, particularly dopamine.
2. Step 2: Recall that dopamine is a neurotransmitter involved in reward, pleasure, and motor control. Normally, after dopamine is released into the synaptic cleft, it is reabsorbed into the presynaptic neuron through dopamine transporters.
3. Step 3: Cocaine blocks these dopamine transporters, preventing the reuptake of dopamine into the presynaptic neuron. This leads to an accumulation of dopamine in the synaptic cleft.
4. Step 4: The increased levels of dopamine in the synaptic cleft result in prolonged stimulation of postsynaptic dopamine receptors, which contributes to the euphoric and addictive effects of cocaine.
5. Step 5: Evaluate the provided options. The correct statement is: 'Cocaine blocks the reuptake of dopamine in the synaptic cleft, increasing dopamine levels in the brain.' The other options incorrectly describe mechanisms unrelated to cocaine's primary action.