In relation to the molecular mechanism of action of sympathomimetics, the following is CORRECT:

Correct Answer: D

Rationale: The correct answer is D: Alpha 1 receptor stimulation releases IP3 and DAG. When alpha 1 receptors are stimulated by sympathomimetics, they activate G-proteins which then stimulate phospholipase C. Phospholipase C cleaves phosphatidylinositol 4,5-bisphosphate (PIP2) into inositol trisphosphate (IP3) and diacylglycerol (DAG). IP3 triggers the release of calcium from intracellular stores, leading to smooth muscle contraction, while DAG activates protein kinase C to initiate various cellular responses. Choices A, B, and C are incorrect because beta receptor stimulation increases cAMP, alpha 2 receptor stimulation inhibits adenyl cyclase leading to decreased cAMP levels, and alpha 2 receptor stimulation does not increase cAMP.

Correct Answer: B

Rationale: Propranolol is a non-selective beta-blocker that can cause bronchoconstriction, making it contraindicated in bronchial asthma. It can worsen asthma symptoms by blocking beta-2 receptors in the lungs. Angina pectoris, hypertension, and arrhythmia are conditions where propranolol is commonly used due to its beta-blocking effects on the heart and blood vessels.

Correct Answer: C

Rationale: The correct answer is C: Amitriptyline. Amitriptyline is a tricyclic antidepressant known for its anticholinergic properties, causing dry mouth, constipation, blurred vision, and urinary retention. Anticholinergic effects result from blocking the action of acetylcholine in the parasympathetic nervous system. Codeine (A) is an opioid, Ciprofloxacin (B) is an antibiotic, and Propranolol (D) is a beta-blocker, none of which are expected to cause significant anticholinergic effects.

Correct Answer: D

Rationale: The correct answer is D because organophosphate insecticides and nerve gases inhibit acetylcholine metabolism by irreversibly binding to acetylcholinesterase enzyme, leading to accumulation of acetylcholine at synapses. This results in overstimulation of cholinergic receptors, causing symptoms of cholinergic toxicity. Choice A is incorrect because alpha and beta-adrenergic receptors are not the targets of organophosphates. Choice B is incorrect because organophosphates do not block all muscarinic receptors. Choice C is incorrect because organophosphates do not specifically target nicotinic receptors in the brain.

Correct Answer: D

Rationale: The correct answer is D: scurvy. Scurvy is caused by a deficiency of vitamin C, leading to symptoms such as fatigue, bleeding gums, and skin discoloration. Vitamin C is essential for collagen synthesis, and its deficiency impairs collagen formation. A: AIDS is caused by the human immunodeficiency virus (HIV), not by a lack of vitamin C. B: Coronary heart disease is primarily related to factors such as high cholesterol, high blood pressure, and smoking, not vitamin C deficiency. C: Rickets is caused by a deficiency of vitamin D, leading to soft and weak bones, not by a lack of vitamin C.