Pharmacology - Problem Drill 06: Autonomic Pharmacology - Adrenergic System

Transcription

1 Pharmacology - Problem Drill 06: Autonomic Pharmacology - Adrenergic System Question No. 1 of 10 Instructions: (1) Read the problem and answer choices carefully, (2) Work the problems on paper as 1. What are adrenergic neurons? Question #01 (A) Adrenergic neurons exert their effects through the neurotransmitter norepinephrine. (B) Adrenergic neurons exert their effects through the neurotransmitter isoproterenol. (C) Are neurons that utilize a neurotransmitter produced in the thyroid. (D) Are neurons that utilize the neurotransmitter made from dopamine which is produced in the thyroid. (E) They are special neurons located entriely in the central nervous system. A. Correct! Adrenergic neurons exert their effects through the neurotransmitter norepinephrine. Isoproterenol is a synthetic sympathomimetc that selectively activates beta receptors. The neurotransmitter norepinephrine is synthesized from dopamine which is released from adrenergic neurons. Along with adrenergic neurons, norepinephrine is made in the adrenal medulla from dopamine. Adrenergic neurons are part of the peripheral nervous system and the sympathetic division. Adrenergic neurons exert their effects through the neurotransmitter noradrenaline or norepinephrine (NE). In the adrenal medulla, NE is converted to epinephrine (adrenaline) by phenylethanolamine N-methyl-transferase. The correct answer is (A).

2 Question No. 2 of 10 Instructions: (1) Read the problem and answer choices carefully, (2) Work the problems on paper as 2. What is norepinephrine? Question #02 (A) A neurotransmitter which is stored in adrenergic neurons and released due to dopamine stimulation. (B) Norepinephrine is produced from dopamine, and is released through calcium mediated exocytosis. (C) A molecule that is only used as a neurotransmitter in the human body. (D) A molecule that is converted into dopamine, prior to exerting its action. (E) A neurotransmitter that has equal affinity for both α-receptors and β- receptors. Norepinephrine is produced from dopamine, but is released through calcium mediated exocytosis. B. Correct! Norepinephrine is produced from dopamine, and is released through calcium mediated exocytosis. Norepinephrine is both a neurotransmitter and hormone. Norepinephrine is converted into epinephrine in the adrenal medulla. Norepinephrine has an increased affinity for both α-receptors and β-receptors. Norepinephrine (NE) is transported into and stored at high concentrations in the synaptic vesicles and is released through calcium mediated exocytosis. The action of NE is terminated mainly by reuptake into the nerve terminals, which can be blocked by tricyclic antidepressants. The correct answer is (B).

3 Question No. 3 of 10 Instructions: (1) Read the problem and answer choices carefully, (2) Work the problems on paper as 3. Which of the following statements about α-adrenergic receptors is correct? Question #03 (A) α-adrenergic receptors have a higher affinity for epinephrine than isoproterenol. (B) α-adrenergic receptors have no affinity for epinephrine as part of their potency profile. (C) Specialized receptors that exert their effects through guanylyl cyclase receptors. (D) There is only a single α-adrenoreceptor subtype, designated α1. (E) Vasoconstriction is not an effect of α-adrenoreceptors. A. Correct! α-adrenergic receptors have a higher affinity for epinephrine than isoproterenol. α-adrenergic receptors have a higher affinity for epinephrine than isoproterenol. G-protein coupled receptors are used in α-adrenergic receptor function. There are at least 2 α-adrenoreceptor subtypes, α1, and α2. α1 adrenoreceptors cause vasoconstriction upon activation. There are two α-adrenoceptor subtypes and three β subtypes. All exert their effects through G-protein coupled receptors (GPCR). The primary effects of activation of alpha receptor subtypes include: α1: vasoconstriction, relaxation of gastro-intestinal smooth muscle, salivary secretion and hepatic glycogenolysis; α2: inhibition of release of neurotransmitter, platelet aggregation and contraction of vascular smooth muscle. The correct answer is (A).

4 Question No. 4 of Which of the following statements about β-adrenergic receptor subtypes is correct? Question #04 (A) β-adrenergic receptor subtypes have the following relative potency profile: epinephrine>norepinephrine>>isoproterenol. (B) β-adrenergic receptor subtypes have the following relative potency profile: isoproterenol>epinephrine>norepinephrine. (C) Activation of β2 receptors leads to vasoconstriction. (D) β2 receptors are found in the liver and heart. (E) β3 receptors are involved in bronchodilation. β-adrenergic receptor subtypes have the following relative potency profile: isoproterenol>epinephrine>norepinephrine. B. Correct! β-adrenergic receptor subtypes have the following relative potency profile: isoproterenol>epinephrine>norepinephrine. β2 receptor activation leads to vasodilation. β2 receptors are found in the lungs. β3 receptors are involved in lipolysis. The primary effects of activation of the β receptor subtypes include: (1) β1: increased cardiac rate and force of contraction, relaxation of gastrointestinal smooth muscle, (2) β2: bronchodilation, vasodilation, relaxation of visceral smooth muscle, hepatic glycogenolysis and muscle tremor, (3) β3: lipolysis. The correct answer is (B).

5 Question No. 5 of 10 Instructions: (1) Read the problem statement and answer choices carefully, (2) Work the problems on paper as 5. Which of the following sympathomimetic(s) are primarily selective for the β1 adrenoreceptor subtype? Question #05 (A) Phenylephrine and Oxymetazoline. (B) Albuterol, Terbutaline. (C) Dopamine. (D) Dobutamine. (E) Dobutamine and Terbutaline. Phenylephrine and Oxymetazoline are primarily selective for α1 adrenoreceptors. Albuterol, Terbutaline are primarily selective for β2 adrenoreceptors. Dopmaine is a neurotransmitter that activates dopamine receptors D 1 D 5. D. Correct! Dobutamine is primarily selective for β1 adrenoreceptors. While dobutamine is primarily selective for β1 adrenoreceptors, Terbutaline is primarily selective for β2 adrenoreceptors. Selective drugs exist for the four main receptor subtypes of adrenoceptors: α1, α2, β1 and β2. All sympathomimetics are derived from phenylethylamine. The different substitutions affect the receptor selectivity. α1: phenylephrine and oxymetazoline α2: clonidine and methylnoradrenaline β1:dobutamine β2:albuterol, terbutaline The correct answer is (D).

6 Question No. 6 of Which of the following statements about sympathomimetics is correct? Question #06 (A) Sympathomimetics can be divided into three categories: direct-acting, indirect-acting and sympathetic stimulators. (B) Sympathomimetics can be divided into three categories: direct-acting, indirect-acting and mixed action. (C) Epinephrine is an example of an indirect-acting sympathomimetic. (D) All sympathomimetics are derivatives of ethanolamine. (E) Indirect-acting sympathomimetics cause the degradation of catecholamines. Sympathomimetics can be divided into three categories: direct-acting, indirectacting and mixed action. B. Correct! Sympathomimetics can be divided into three categories: direct-acting, indirectacting and mixed action. Epinephrine is an example of a direct-acting sympathomimetic. All sympathomimetics are derivatives of phenylethylamine. Indirect-acting sympathomimetics cause the release of catecholamines. Sympathomimetics can be further divided into three categories: direct acting, indirect acting, and mixed action (with both direct and indirect actions). Sympathomimetics that are classified as direct-acting include: Epinephrine and Phenylephrine. Indirect-acting sympathomimetics cause the release of catecholamines that then activate adrenergic receptors. An example is amphetamine, which causes the release of catecholamines. Some drugs act as both agonists and antagonists within the autonomic nervous system. Ephedrine is a mixed action sympathomimetic that is found naturally in Ma-Huang and has been used in Chinese medicine for centuries. It is absorbed into the central nervous system where it acts as a mild stimulant. It is a noncatechol phenylisopropylamine and therefore has a long duration of action and a high bioavailability. Pseudoepherine, an ephedrine enantiomer, is a derivative of ephedrine that is widely used as a decongestant. The correct answer is (B).

7 Question No. 7 of What is amphetamine? Question #07 (A) Amphetamine is an example of a direct-acting sympathomimetic. (B) It s a drug that depresses the central nervous system. (C) Amphetamine causes the release of catecholamines. (D) Amphetamine is an example of an indirect-acting sympathomimetic that blocks the release of catecholamines. (E) A sympathomimetic that has no impact on norepinephrine. Amphetamine is an example of a indirect-acting sympathomimetic. Amphetamine is a stimulant that readily enters the central nervous system. C. Correct! Amphetamine causes the release of catecholamines. Amphetamine is an example of an indirect-acting sympathomimetic; however it leads to the release of catecholamines. Amphetamine causes the release of catechcolamines such as norepinephrine. Indirect-acting sympathomimetics cause the release of catecholamines that then activate adrenergic receptors. An example is amphetamine, which causes the release of catecholamines. It has similar effects to ephedrine. Amphetamine enters the central nervous system more readily and leads to alertness and appetite suppressant effects. The correct answer is (C).

8 Question No. 8 of Epinephrine. Question #08 (A) Is an indirect-acting adrenergic agonist. (B) Is a potent vasodilator and cardiac stimulant. (C) Activates β1 receptors causing vasoconstriction. (D) Activates β1 receptors for a positive inotropic and chronotropic effect on the heart. (E) Only activates β1 receptors. Epinephrine is a direct-acting adrenergic agonist. Epinephrine is a potent vasoconstrictor and cardiac stimulator. Epinephrine activates β1 receptors for a positive inotropic and chronotropic effect on the heart. D. Correct! Epinephrine activates β1 receptors for a positive inotropic and chronotropic effect on the heart. Epinephrine activates both α-receptors and β1 receptors. Epinephrine is a direct acting adrenergic agonist. It is a potent vasoconstrictor and cardiac stimulant, activates β1- receptors for a positive inotropic and chronotropic effect on the heart, and activates α-receptors causing vasoconstriction. The correct answer is (D).

9 Question No. 9 of Which of the following statements about α-adrenoreceptor antagonists is correct? Question #09 (A) α-adrenoreceptor antagonists can be classified into reversible and nonreversible. (B) α-adrenoreceptor antagonists can be classified into reversible and crossstable. (C) The main side effects of α-adrenoreceptor antagonists are related to respiratory stimulation. (D) Phenoxybenzamine is a reversible non-specific α-adrenoreceptor antagonist. (E) Prazosin, dopamine and doxazosin are examples of selective α- adrenenoreceptor antagonists. A. Correct! α-adrenoreceptor antagonists can be classified into reversible and non-reversible. α-adrenoreceptor antagonists can be classified into reversible and non-reversible. The main side effects of α-adrenoreceptor antagonists are related to cardiac stimulation. Phenoxybenzamine is a non-reversible, non-specific α-adrenoreceptor antagonist. Prazosin, doxazosin, and terazosin are examples of selective α-adrenenoreceptor antagonists. α-adrenoceptor antagonists can be classified as: (1) Reversible - phentolamine and prazosin; or (2) Non-reversible - phenoxybenazmine. The main side effects are related to cardiac stimulation, such as severe tachycardia, arrhythmias, and myocardial ischemia; with oral administration, side effects can be nasal congestion and headache. Phenoxybenzamine: Used with β-antagonists in preparation for surgery. This drug is relatively selective for α1-adrenoceptor receptors; it also blocks histamine, acetylcholine and serotonin receptors. The side effects include nasal congestion, tachycardia, postural hypotension, inhibition of ejaculation, and also non-specific effects, such as fatigue, sedation and nausea. The correct answer is (A).

10 Question No. 10 of β-adrenoreceptor antagonists. Question #10 (A) Are also known as α-blockers. (B) Are primarily used for the management of pulmonary function. (C) Such as propranolol and oxprenolol are selective members. (D) Such as propranolol and oxprenolol are non-selective members. (E) Are only used for cardiovascular diseases. β-adrenoreceptor antagonists are also known as β-blockers. β-adrenoreceptor antagonists are primarily used for the management of arrhythmias, cardioprotection and hypertension. Such as propranolol, alprenolol and oxprenolol are non-selective β-adrenoreceptor antagonists. D. Correct! Such as propranolol, alprenolol and oxprenolol are non-selective β-adrenoreceptor antagonists. β-adrenoreceptor antagonists are used for cardiovascular diseases, as well as migraine and benign essential tremors. β-adrenoreceptor antagonists are also known as β-blockers. This class of drugs is used primarily for the management of arrhythmias, cardioprotection and hypertension. Non-selective members from this group include: propranolol, alprenolol, and oxprenolol. Atenolol is a β1-selective antagonist. Alprenolol and oxprenolol have been shown to have partial agonist activity. The correct answer is (D).