Which of the following could antagonize renal vasodilation induced by dopamine:

Correct Answer: D

Rationale: The correct answer is D: Haloperidol. Haloperidol is a dopamine receptor antagonist, which means it blocks dopamine receptors. Dopamine induces renal vasodilation by acting on dopamine receptors in the kidneys. Therefore, blocking these receptors with haloperidol would antagonize the renal vasodilation effect of dopamine. A: Propranolol is a beta-blocker that acts on beta receptors, not dopamine receptors. B: Atropine is a muscarinic antagonist and does not affect dopamine receptors. C: Prazosin is an alpha-1 adrenergic antagonist and does not target dopamine receptors.

Correct Answer: D

Rationale: Adrenaline is a sympathomimetic drug that acts on adrenergic receptors. In acute situations like allergic reactions, bronchial asthma, and heart block, adrenaline can be beneficial due to its bronchodilator and vasoconstrictor effects. However, in angina pectoris, which is caused by reduced blood flow to the heart muscle, the vasoconstrictor effect of adrenaline can worsen the condition by increasing the workload of the heart. Therefore, adrenaline should not be used in angina pectoris.

Correct Answer: C

Rationale: Rationale: Labetalol is a non-selective beta-blocker that reduces cardiac contractility by blocking beta-1 receptors and inhibits sympathetic-mediated vasoconstriction by blocking alpha-1 receptors. Albuterol (A) is a beta-2 agonist, which increases cardiac contractility. Atropine (B) is a muscarinic antagonist, which increases heart rate and does not affect vasoconstriction. Isoproterenol (D) is a non-selective beta agonist, which increases cardiac contractility and vasodilation. Thus, C (Labetalol) is the only drug that can lower blood pressure by both mechanisms.

Correct Answer: B

Rationale: Step 1: MAO inhibitors prevent the breakdown of neurotransmitters like norepinephrine. Step 2: Pseudoephedrine stimulates the release of norepinephrine. Step 3: The combination can lead to excessive norepinephrine, causing hypertension and potential stroke. Therefore, the likely outcome when a patient taking an MAO inhibitor also takes pseudoephedrine is a hypertensive crisis and possible stroke (Choice B). Summary: - Choice A (acute bronchospasm/asthma due to ACh release from the adrenal medulla) is incorrect because pseudoephedrine does not directly cause this response. - Choice C (heart rate and contractile force would drop significantly and quickly) is incorrect as pseudoephedrine tends to increase heart rate and blood pressure. - Choice D (the cold symptoms would quickly get worse - increased secretions) is incorrect as pseudoephedrine is a decongestant and would not worsen cold symptoms

Correct Answer: D

Rationale: The male labeled X must carry both brown and black coat color genes as it is brown. When mated with a black female, the male will pass on either a brown or black gene to the offspring. This results in a 1:1 ratio of brown to black coat color in the offspring. All black (A) and all brown (B) are incorrect as the male carries both genes. The 3:1 ratio (C) is not applicable here as the male can pass on either brown or black gene equally.