Indicate the direct-acting sympathomimetic, which is an alfa1 alfa2 beta1 receptor agonist:

Correct Answer: D

Rationale: Step-by-step rationale: 1. Norepinephrine is a direct-acting sympathomimetic that stimulates alpha1, alpha2, and beta1 receptors. 2. Activation of alpha1 receptors causes vasoconstriction. 3. Activation of alpha2 receptors inhibits norepinephrine release. 4. Activation of beta1 receptors increases heart rate and contractility. Summary: A. Isoproterenol is a non-selective beta agonist. B. Ephedrine acts mainly by releasing norepinephrine. C. Dobutamine is a beta1-selective agonist. D. Norepinephrine is the correct choice as it stimulates alpha1, alpha2, and beta1 receptors.

Correct Answer: D

Rationale: The correct answer is D because barbiturates act by increasing the duration, frequency, and direct activation of GABA-gated Cl- channels. This leads to hyperpolarization of neurons, resulting in sedative and hypnotic effects. Choice A is correct as barbiturates prolong the opening of Cl- channels. Choice B is incorrect as barbiturates enhance, not directly activate, the Cl- channels. Choice C is incorrect as barbiturates increase the duration, not frequency, of Cl- channel opening events. Therefore, the correct answer is D as it encompasses all the mechanisms of barbiturate action.

Correct Answer: B

Rationale: The correct answer is B: Inhibition of GABA aminotransferase. Vigabatrin increases GABA levels by inhibiting GABA aminotransferase enzyme, which is responsible for GABA breakdown. This leads to enhanced GABAergic inhibition in the brain. A: Direct action on the GABA receptor-chloride channel complex is incorrect as vigabatrin does not directly bind to GABA receptors. C: NMDA receptor blockade via the glycine binding site is incorrect as vigabatrin does not affect NMDA receptors. D: Inhibition of GABA neuronal reuptake from synapses is incorrect as vigabatrin does not affect GABA reuptake mechanisms.

Correct Answer: C

Rationale: Rationale: 1. Tolcapone inhibits catechol-O-methyltransferase (COMT), reducing levodopa peripheral metabolism. 2. By prolonging levodopa's action, it enhances its efficacy in treating Parkinson's disease. 3. Carbidopa enhances levodopa bioavailability, not directly affecting its peripheral metabolism. 4. Clozapine is an antipsychotic with no COMT inhibitory activity. 5. Rasagiline is a monoamine oxidase-B inhibitor, not a COMT inhibitor.

Correct Answer: D

Rationale: The correct answer is D: All of the above. Alcohol potentiates SNS depressants by enhancing their sedative effects, vasodilators by causing further relaxation of blood vessels, and hypoglycemic agents by lowering blood sugar levels. This occurs due to alcohol's ability to enhance the effects of these substances, leading to increased sedation, blood vessel dilation, and blood sugar reduction when combined. Therefore, choosing any of the other options would be incorrect as they do not encompass the full range of substances that alcohol can potentiate.