Characteristics of epinephrine include all of the following EXCEPT:

Correct Answer: B

Rationale: The correct answer is B: Epinephrine is not synthesized in the nerve endings. It is produced in the adrenal medulla and released into the bloodstream in response to stress. It travels through the blood to target tissues where it interacts with adrenoreceptors, leading to various physiological responses. Epinephrine does not directly interact with nerve endings for synthesis or action. Choices A, C, and D are incorrect because epinephrine is indeed synthesized in the adrenal medulla, transported in the blood to target tissues, and directly interacts with and activates adrenoreceptors, respectively.

Correct Answer: C

Rationale: The correct answer is C because reserpine actually causes a sympatholytic effect, not a sympathomimetic effect. Reserpine depletes norepinephrine and serotonin stores in the brain, leading to decreased sympathetic activity. Choices A, B, and D are incorrect because reserpine does inhibit the uptake of norepinephrine, decrease cardiac output and peripheral resistance, and deplete catecholamines and serotonin stores in the brain, respectively.

Correct Answer: C

Rationale: The correct answer is C: Phenobarbital. Phenobarbital enhances GABA-mediated inhibition by increasing the duration of GABA-A receptor channel opening, leading to increased chloride ion influx. This enhances inhibitory neurotransmission, reducing neuronal excitability and seizure activity. Ethosuximide (A) works by blocking T-type calcium channels, Carbamazepine (B) by blocking voltage-gated sodium channels, and Lamotrigine (D) by inhibiting sodium channels and reducing glutamate release, none of which directly enhance GABA-mediated inhibition.

Correct Answer: A

Rationale: The correct answer is A: TRUE. In Parkinson's disease, there is a reduction in dopamine levels in the basal ganglia, leading to the characteristic motor symptoms. This is due to the degeneration of dopamine-producing neurons in the substantia nigra. Choice B is incorrect because the statement is true. Choice C (None) and D (All) are incorrect as they do not provide any meaningful explanation.

Correct Answer: D

Rationale: The correct answer is D because fentanyl can produce significant respiratory depression by inhibiting brain stem respiratory mechanisms (choice A) and by causing truncal rigidity (choice C). Inhibiting brain stem respiratory mechanisms affects the control of breathing, leading to decreased respiratory rate and depth. Truncal rigidity can impair chest wall movement, further reducing respiratory function. Choice B, suppression of the cough reflex leading to airway obstruction, is incorrect as it does not directly relate to respiratory depression caused by fentanyl.