Beta adrenoreceptor subtypes is contained in all of the following tissues EXCEPT:

Correct Answer: C

Rationale: The correct answer is C: Pupillary dilator muscle. Beta adrenoreceptor subtypes are found in bronchial muscles, heart, and fat cells, but not in pupillary dilator muscles. These receptors are involved in various functions such as bronchodilation, cardiac stimulation, and lipolysis. Pupillary dilator muscles are predominantly innervated by alpha adrenergic receptors, not beta adrenergic receptors, which regulate pupil constriction. Thus, the absence of beta adrenoreceptor subtypes in pupillary dilator muscles makes choice C the correct answer.

Correct Answer: C

Rationale: The correct answer is C: Thyopental. Thyopental is a barbituric acid derivative known for its hypnotic properties by inducing sleep. Flurazepam (A) is a benzodiazepine used for treating insomnia. Zaleplon (B) is a non-benzodiazepine hypnotic agent. Triazolam (D) is also a benzodiazepine used for insomnia. Therefore, the correct choice is C as it is the only barbituric acid derivative among the options.

Correct Answer: A

Rationale: The correct answer is A because phenytoin blocks sodium channels, inhibiting the abnormal firing of neurons seen in epilepsy. This action helps to stabilize neuronal membranes and prevent seizures. Options B, C, and D are incorrect as phenytoin does not bind to GABA receptors, affect Ca2+ currents, or inhibit GABA-transaminase. These mechanisms are associated with different antiepileptic drugs.

Correct Answer: B

Rationale: The correct answer is B because carbidopa inhibits dopa decarboxylase enzyme, preventing the conversion of levodopa into dopamine outside the brain. This allows more levodopa to reach the brain and be converted into dopamine, improving its efficacy in treating Parkinson's disease. Choice A is incorrect as carbidopa does not directly affect the synthesis, release, or reuptake of dopamine. Choice C is incorrect because carbidopa does not stimulate dopamine receptors but rather works on the enzymatic conversion of levodopa to dopamine. Choice D is incorrect as carbidopa does not inhibit catechol-O-methyltransferase (COMT), which is another enzyme involved in dopamine metabolism.

Correct Answer: D

Rationale: The correct answer is D because intravenous morphine in dyspnea from pulmonary edema helps in reducing the perception of shortness of breath, patient anxiety, and also reduces cardiac preload and afterload. Morphine acts as a vasodilator, reducing venous tone and decreasing peripheral resistance, which in turn reduces cardiac preload and afterload. This leads to improved cardiac function and decreased workload on the heart, resulting in relief from dyspnea. Choices A, B, and C are all interconnected mechanisms through which morphine exerts its effects in alleviating dyspnea in pulmonary edema.