Question

Two new synthetic drugs (X and Y) are to be studied for their cardiovascular effects. The drugs are given to three anesthetized animals while the blood pressure is recorded. The first animal has received no pretreatment (control), the second has received an effective dose of a long-acting ganglion blocker, and the third has received an effective dose of a long-acting muscarinic antagonist. Drug X caused a 50 mm Hg rise in mean blood pressure in the control animal, no blood pressure change in the ganglion-blocked animal, and a 75 mm mean blood pressure rise in the atropine-pretreated animal. Drug X is probably a drug similar to

(A) Acetylcholine
(B) Atropine
(C) Epinephrine
(D) Hexamethonium
(E) Nicotine

Answer 1

Drug X induces a rise in blood pressure and its effect is neutralized by a ganglion blocker but intensified by atropine, indicating it is a sympathomimetic drug similar to epinephrine.

Step-by-step explanation:

Analyzing the effects of Drug X on cardiovascular activity in different scenarios, we can deduce the nature of this synthetic drug. In the control animal, Drug X caused a 50 mm Hg rise in mean blood pressure, suggesting a sympathomimetic effect, similar to the natural action of norepinephrine or epinephrine. The lack of blood pressure change in the animal treated with a ganglion blocker indicates that Drug X's effects are dependent on the autonomic ganglia, which are involved in the sympathetic nervous system's regulation of blood pressure. Finally, the 75 mm Hg rise in blood pressure in the muscarinic antagonist pretreated animal suggests that Drug X may have some level of parasympathetic interaction as well, evidenced by a more significant effect when parasympathetic action is blocked by atropine. Based on this information, Drug X most closely resembles Epinephrine (Option C), a sympathomimetic drug that increases blood pressure by acting on adrenergic receptors and would have no effect when ganglionic transmission is blocked.