Wrong. Cocaine itself does not produce vasoconstriction and, therefore, it cannot increase the maximal effect of norepinephrine. Go back to Item VI.

Right. Phentolamine pretreatment would block the alpha adrenergic receptors, but since phentolamine is a competitive inhibitor, a large dose of norepinephrine would still slightly increase the blood pressure. At the same time, phentolamine would not affect the increase of heart rate produced by stimulation of beta adrenergic receptors. However, there is one more drug which would also produce this effect. Go back to Item XIV and try to find it.

Wrong. The maximal effect produced by drug B is larger than the maximal effect of drug A, which indicates that drug B might have higher intrinsic activity. However, the dose of drug B which is required to produce effect Y is higher than an equipotent dose of drug A. Since potency varies inversely with the magnitude of the dose required to produce a given effect, drug A is more potent than drug B. Go back to Item I and try again.

Wrong. A low dose of epinephrine would increase heart rate, but at the same time it would decrease blood pressure because it would produce vasodilation through stimulation of adrenergic beta receptors. Go back to Item XII.

Wrong. Isoproterenol and norepinephrine have different potencies at cardiac adrenergic receptors. Go back to Item V.

Wrong. Phenoxybenzamine is not a reversible competitive antagonist of phenylephrine. Therefore, in a preparation treated with phenoxybenzamine, even high doses of phenylephrine will not produce a substantial increase of the blood pressure. Go back to Item IX.

Wrong. Succinylcholine modifies the effect of acetylcholine on skeletal muscle. Before you go back to Item VIII, review the pharmacological effects and mechanisms of action of succinylcholine and other neuromuscular blocking agents.

Wrong. Go back to Item XV and reconsider.

Right. Propranolol would diminish or abolish the increased heart rate produced by epinephrine because it blocks cardiac beta adrenergic receptors. There is, however, another drug which would also modify the epinephrine effect. Go back to Item XVI and think about it again.

Wrong. There is only one true statement listed. Go back to Item XVIII and try to find it.

Right. Isoproterenol stimulates chiefly beta adrenergic receptors and would, therefore, produce tachycardia and decrease the blood pressure, due to peripheral vasodilation. There is, however, another treatment which would produce similar changes. Go back to Item XVII and try to find it.

Wrong. D-tubocurarine is a reversible competitive antagonist of acetylcholine. By increasing the dose of acetylcholine, it is possible to obtain the same maximal effect in the presence of d-tubocurarine as with acetylcholine alone. Go back to Item X.

Wrong. There is one treatment listed which does not simultaneously decrease the blood pressure and increase the heart rate. Go back to Item XIX and try to find it.

Right. Statements b and d are both correct. A decrease in the Emax with no shift in the EC50 is seen either in the presence of a non-competitive antagonist or after treatment with an irreversible competitive antagonist.

Right. Hexamethonium would increase the tachycardia induced by epinephrine, because it prevents the reflex cholinergic inhibition of the heart rate evoked by the increased blood pressure. There is, however, another drug which would also modify the effect of epinephrine. Go back to Item XVI and think about it again.

Very good. I hope you considered statement a and c to be true. If you did, you have a good understanding of the concepts of potency and intrinsic activity. If you thought that statement b is true, you should review the comment to Item Ib. Now you can go to Item II.

Wrong. Isoproterenol decreased blood pressure by stimulating beta receptors; this effect would be unaffected or enhanced by phenoxybenzamine pretreatment. Go back to Item XVIII.

Right. Phentolamine blocks alpha adrenergic receptors; therefore epinephrine, in a preparation pretreated with phentolamine, stimulates only beta receptors and produces tachycardia and vasodilation. There is, however, another treatment which would produce similar changes. Go back to Item XVII and try to find it.

Wrong. Phenylephrine would increase blood pressure by producing vasoconstriction, but this increase of blood pressure would induce bradycardia through stimulation of carotid baroreceptors. Go back to Item XII.

Wrong. You either skipped or forgot Item XI. Go back to Item XI before trying to answer Item XIX again.

Wrong. Physiological antagonism is caused by agonist and antagonist acting at two independent sites and inducing independent, but opposite, effects. Atropine acts at the same site as acetylcholine. Go back to Item II.

Right. Phenelzine inhibits monamine oxidase, the enzyme which metabolizes many biogenic amines. Some kinds of heavy cheese have a high content of substances, mainly tyramine, which can produce an increase in blood pressure. Normally, after ingestion of such cheese, these substances are broken down rapidly by monamine oxidase. In a patient treated with phenelzine, metabolism of these amines is inhibited, and, therefore, they can produce a dangerous rise of blood pressure accompanied by a reflex bradycardia. There is, however, another drug or drug combination which would induce similar changes. Go back to Item XVI and try to find it.

Wrong. Physostigmine does not have an effect by itself and, therefore, it cannot increase the maximal effect of acetylcholine. Go back to Item IV.

Wrong. D-tubocurarine modifies the pharmacological effect of acetylcholine on skeletal muscles. Before you go back to Item X, review the pharmacological effects and mechanisms of action of d-tubocurarine and other neuromuscular blocking agents.

Wrong. Albuterol is a selective B₂ agonist and therefore would be expected to activate vasodilator B₂ receptors, decrease total peripheral resistance, and decrease blood pressure, reflex effects, and (at higher concentrations) effects on B₁ receptors might cause an increased heart rate. (Recall that this drug is administered by inhalation to treat asthma, in order to increase the selectivity of its effects on pulmonary B₂ receptors and decrease the risk of cardiovascular side effects such as tachycardia.) Go back to Item XV.

Wrong. Cocaine potentiates the effects of norepinephrine. That means that the same dose of norepinephrine will produce a greater effect in the presence of cocaine. Curve D indicates a smaller effect of the same dose than Curve C. Go back to Item VI.

Right. Succinylcholine is a depolarizing neuromuscular blocking agent which prevents the effect of acetylcholine by initially depolarizing the membrane (phase I) and then desensitizing the receptors (phase II). Therefore, its blockade cannot be abolished by increasing the dose of acetylcholine.

Wrong. Isoproterenol is not less potent than norepinephrine at cardiac receptors. Go back to Item V.

Wrong. Pretreatment with phenoxybenzamine modifies the effect of phenylephrine on blood vessels. Before you go back to Item IX, review the pharmacological effects and mechanisms of action of phenoxybenzamine and other sympathetic blocking agents.

Wrong. The effect of norepinephrine in a preparation pretreated with phentolamine is represented by a different curve. Go back to Item VII.

Very good. I hope you consider a and b as the right answers. Go to Item XV.

Wrong. An irreversible competitive antagonist acts by decreasing the number of receptors available for binding an agonist. Therefore even high agonist concentration cannot overcome an irreversible blockade, and the maximal effect of an agonist is smaller in the presence than in the absence of an irreversible antagonist. Go back to Item III.

Wrong. Atropine would abolish the effect of vagal nerve stimulation but it would not decrease the response to carotid occlusion. Go back to Item XIII.

Wrong. All of the drugs listed, as well as vagus nerve stimulation, would induce a decrease in blood pressure. However, only one of these conditions would produce a decrease of the heart rate also. Go back to Item XI and try to find it.