Atropine is highly selective for:

Correct Answer: D

Rationale: The correct answer is D: All of the above. Atropine is a non-selective muscarinic antagonist, blocking all muscarinic receptor subtypes (M1, M2, and M3). This is due to its structure and mechanism of action, which allows it to bind and inhibit all types of muscarinic receptors. Atropine's broad action leads to its multiple effects, such as blocking parasympathetic stimulation and increasing heart rate. Choices A, B, and C are incorrect because atropine does not selectively target only one specific muscarinic receptor subtype.

Correct Answer: D

Rationale: Step 1: Long-acting decongestants are preferred for sustained relief. Step 2: Xylometazoline has a longer duration of action compared to other choices. Step 3: Epinephrine and norepinephrine are short-acting sympathomimetic agents. Step 4: Phenylephrine is intermediate-acting, not long-acting. Step 5: Therefore, D (Xylometazoline) is the correct choice for long-acting topical decongestant agents.

Correct Answer: C

Rationale: The correct answer is C: Reserpine. Reserpine is a rauwolfia alkaloid acting as an adrenoreceptor antagonist by inhibiting the storage of norepinephrine and serotonin in vesicles. Prazosin (A) is an alpha-1 adrenergic receptor antagonist, Propranolol (B) is a non-selective beta-adre, Phentolamine (D) is a non-selective alpha-adrenergic receptor antagonist, making them all incorrect choices.

Correct Answer: D

Rationale: The correct answer is D. Antiseizure drugs work through multiple mechanisms to prevent seizures. 1. A: Antiseizure drugs enhance GABAergic transmission, increasing inhibition in the brain. 2. B: They also diminish excitatory glutamatergic transmission, reducing neuronal excitation. 3. C: Antiseizure drugs modify ionic conductance to stabilize neuronal activity. Therefore, the correct answer is D, as antiseizure drugs act through all the mentioned mechanisms to prevent seizures effectively. Choices A, B, and C are incorrect because they do not encompass the comprehensive range of mechanisms involved in the action of antiseizure drugs.

Correct Answer: C

Rationale: The correct answer is C: Dopamine. Parkinson's disease is characterized by a loss of dopamine-producing neurons in the brain. Dopamine is crucial for controlling movement and coordination, and its deficiency leads to symptoms of Parkinson's. Acetylcholine (Choice A) is not primarily involved in Parkinson's disease, and excess glutamate (Choice B) can actually be harmful in neurodegenerative disorders. Choice D is incorrect as acetylcholine and glutamate are not directly related to Parkinson's disease.