Pharmacodynamics involves the study of following?

Correct Answer: A

Rationale: Pharmacodynamics is the study of how drugs interact with the body to produce their effects, focusing on mechanisms of drug action. This includes drug-receptor interactions, signal transduction pathways, and physiological responses. Biotransformation (choice B), distribution (choice C), and excretion (choice D) are aspects of pharmacokinetics, not pharmacodynamics. Pharmacokinetics deals with drug absorption, distribution, metabolism, and excretion in the body. Therefore, choice A is the correct answer as it directly relates to the study of pharmacodynamics.

Correct Answer: B

Rationale: The correct answer is B: Edrophonium. Edrophonium is an indirect-acting cholinomimetic agent because it works by inhibiting acetylcholinesterase enzyme, leading to an increase in acetylcholine levels at the synaptic cleft. This results in enhanced cholinergic transmission. On the other hand, choices A, C, and D are direct-acting cholinomimetics. Lobeline (A) acts as a nicotinic receptor agonist, Pilocarpine (C) is a muscarinic receptor agonist, and Carbachol (D) is a non-selective cholinomimetic that directly stimulates both nicotinic and muscarinic receptors without affecting acetylcholinesterase. Therefore, Edrophonium is the only indirect-acting cholinomimetic among the provided options.

Correct Answer: C

Rationale: Hexamethonium is a ganglionic blocker that acts specifically at the autonomic ganglia. It inhibits the action of acetylcholine at the ganglionic nicotinic receptors, leading to the blockade of autonomic functions. This results in the inhibition of sympathetic and parasympathetic responses. Therefore, the correct answer is C: Autonomic ganglia. Muscarinic receptor site (A) is not directly affected by Hexamethonium. Neuromuscular junction (B) is not the primary site of action for this drug. Axonal transmission (D) is not the specific target of Hexamethonium.

Correct Answer: D

Rationale: The correct answer is D because epinephrine acts on different receptors to induce hyperglycemia. Epinephrine stimulates beta2 receptors to increase gluconeogenesis and glycogenolysis, leading to elevated blood glucose levels. It also inhibits insulin secretion from alpha receptors, further contributing to hyperglycemia. Therefore, all options A, B, and C are correct mechanisms through which epinephrine induces hyperglycemia.

Correct Answer: A

Rationale: The correct answer is A because phentolamine is an alpha-adrenergic antagonist that blocks presynaptic alpha2 receptors. By inhibiting these receptors, it increases norepinephrine release, leading to stimulation of unblocked beta receptors on the heart, resulting in tachycardia. This mechanism directly links the action of phentolamine to the observed tachycardia. Choice B (Baroreflex mechanism) is incorrect because phentolamine-induced tachycardia is primarily mediated by the alpha2 receptor antagonism rather than the baroreflex mechanism. Choice C (Direct effect on the heart by stimulation of beta1 receptors) is incorrect because phentolamine does not directly stimulate beta1 receptors on the heart; rather, it indirectly causes cardiac stimulation through enhanced norepinephrine release. Choice D (Inhibition of transmitter reuptake at noradrenergic synapses) is incorrect because phentolamine does not inhibit