CLASS: Fundamentals 2 Scribe: Megan Guthman

CLASS: FUNdamentals 2 Scribe: Megan Guthman

DATE: 12.1.10 Proof: Christine Sirna PROFESSOR: Ku Sympathetic Agonists and Antagonists Part 1 Page 1 of 6

I. DENTAL/OPTOMETRY 2010 [S1] a. This lecture is about autonomic pharmacology: sympathetic. Dr. Pillion will speak about parasympathetic. b. Specifically, we will discuss sympathetic adrenergic agonists and antagonists. II. FIGURE: PSN VS. SNS [S2] a. This is the nervous system (NS). You have a central nervous system (CNS) that signals from systemic to the periphery. You have the heart, and the aortic arch that can send signals to the brain stem. The cardiovascular system is predominantly controlled by autonomic. b. All organs - Kidney, GI tract - are innervated by sympathetic and parasympathetic c. In the cardiovascular system, if the heart is too fast or slow, it sends a signal to the brain stem. The brain stem goes through ganglions: pre- and post-ganglion. More about the CNS in our neuro modules. d. CNS concerns ganglions, we talk about synapses and neurotransmitters in the periphery. e. Two divisions of autonomic pharmacology: parasympathetic and sympathetic. Presynaptic and postsynaptic - how do we modulate the functions of these sympathetic nervous systems? III. SYMPATHETIC NERVE TERMINALS [S3] a. Cartoon illustrates sympathetic nerve terminal that innervates vascular smooth muscle cells or cardiac muscle cells. The neurotransmitter (NT) here is norepinephrine. b. Biosynthesis of neurotransmitters: read in the text how the simple amino acid tyrosine is converted to DOPA  Dopamine  NE  Epi. c. Storage vesicles – store NT’s within them and how they release. Read the text on this. d. There’s always feedback mechanisms – reuptake of norepi back into nerve terminal or presynaptic alpha 2 receptors to downregulate. Too much norepi activates alpha 2 receptors to shut it down, an example of a feedback mechanism. IV. NOREPINEPHRINE SYNTHESIS FIGURE [S4] a. Figure illustrates how tyrosine, an amino acid we get from food, transported into a vesicle, is converted by tyrosine hydroxylase to DOPA. i. Dopamine must be stored in vesicles so it’s not broken down by monoamine oxidase. Must be stored right away so it’s not broken down. Inside vesicles, the dopamine is converted to NE by dopamine beta hydroxylase. The vesicle is transported to the terminal and then released by a calcium-dependent mechanism. b. Lots of ways to modulate this synthetic pathway. i. Alpha-methyltyrosine can inhibit synthesis so there’s less DOPA converted. ii. Methyldopa can inhibit the conversion of DOPA to dopamine. c. Drugs (like L-DOPA) can cause us to make more DOPA to stimulate more dopamine, used for Parkinson’s to control motor activities. d. Can upregulate or downregulate by using different inhibitors. i. Reserpine can block the transporter that transports dopamine into vesicles. Since dopamine isn’t transported into vesicles, it is broken down by MAO. e. Cocaine inhibits reuptake, resulting in a lot of norepi in the synapse area. f. Other systems cause increase of release of vesicles filled with norepi: i. Tyramine increases release ii. Bretylium and Guanadrel inhibit release V. MODULATION OF ADRENERGIC NEUROEFFECTOR JUNCTIONS [S5] a. Summarizes different pathways. b. We focus on peripheral effect. (Green at bottom) NT’s and specific receptors, and their target therapies. VI. DRUGS AFFECTING THE SYMPATHETIC NERVOUS SYSTEM [S6] a. Terminology: i. When a molecule like norepi releases from a nerve terminal, it is called a neurotransmitter. Europeans call it noradrenaline, here we call it norepinephrine. ii. Adrenal medulla produces epinephinre, released into the blood and circles the body as a hormone. Circulating = hormone, target specific = NT. iii. Mimetics; drugs that mimic actions of sympatho-adrenal system. Sympathomimetic, adrenomimetic, or proper way to say is sympathetic agonists. All talking about a synthetic agent mimicking actions. iv. Agents that block or reduce actions- called sympatholytics or sympathoplegics. Proper way to call them: sympathetic antagonists. b. Receptors to be aware of: alpha and beta receptors. i. Alpha receptors have two major families: alpha1 and alpha2. Alpha1 and alpha2 have different subtypes alpha1-A, alpha1-B, etc. CLASS: FUNdamentals 2 Scribe: Megan Guthman

DATE: 12.1.10 Proof: Christine Sirna PROFESSOR: Ku Sympathetic Agonists and Antagonists Part 1 Page 2 of 6 ii. Beta receptors have one family but three different subtypes: beta1, beta2, and beta3. VII. DISTRIBUTION OF ADRENOCEPTOR SUBTYPES [S7] a. X in corner = don’t memorize! b. Alpha1, alpha2, beta1 and beta 2 receptors are expressed and function in almost every tissue in the body. c. Optometry students should know – Alpha1 receptors present in the pupillary dilator muscle and the pilomotor smooth muscle. d. Alpha and beta receptors are present in every tissue of the body. VIII. THERAPEUTIC OVERVIEW – CLINICALLY RELEVANT [S8] a. We need to know about sympathetic drugs – our patients will be on them and we will probably take them too. i. Cardiovascular system – treat all kinds of cardiovascular disease ii. Broncial – people with asthma, ephysema b. Uterine, anaphylaxis, topical - any kind of disease, need sympathomimetic drugs c. OR a sympatholytic drug, an antagonist – treat hypertension, angina pectoris, arrhythmias, heart attack, glaucoma, etc. IX. RECEPTOR SUBTYPES, AGONISTS, ANTAGONISTS [S9] a. Going to talk about agonists and antagonists for each alpha and beta receptor. X. ADRENERGIC AGONISTS [S10] a. Going to talk about their chemistry, the structure-activity relationship, enzyme degradation, direct acting vs. indirect acting, and the signal transduction mechanism. XI. FIGURES [S11] a. Chemistry i. All sympathomimetics have common features. The structure at the top is a general catecholamine. 1. Ring at the top is a catechol: a 6-member ring with hydroxyl groups at C3 and C4. 2. The bottom is ethylamine: 2 carbons followed by nitrogen. 3. Together this makes a catecholamine, which all have these 2 features. ii. The three structures at the bottom (dopamine, epi, norepi) are naturally occurring catecholamines in the body, from nerve terminals or the adrenal medulla. The structures are the same except for a small substitution. b. Isoproterenol is a synthetic catecholamine, substituted at the amino terminal. XII. FIGURES [S12] a. Natural hormone epinephrine activates alpha1, alpha2, beta1 and beta2. Hormone is circulating and will “hit” any tissue that has receptor expressed. If a cell type expresses beta1, epinephrine will get in and activate that. For example, fat cells, skeletal muscle, or liver cells express receptors and epinephrine will activate them. Very versatile. b. Norepinephrine only activates alpha1, alpha2 and beta1. It doesn’t activate beta 2, more selective, but still pretty broad. c. To target therapy, we want something more specific. This is why we synthesize catecholamines. d. Isoproterenol and Dobutamine – synthesized to be selective for beta receptors, no longer has alpha actions, only beta actions. Small substitution in structure makes it only activate beta receptors. i. Dobutamine activates beta1 only, while Isoproterenol activates beta1 and beta2. e. Phenylephrine and Methoxamine – substitution in chemical ring makes them alpha agonists, activate alpha receptors, no longer activate beta receptors. f. Don’t memorize structures! g. Recap: phenylephrine and Methoxamine are NOT catecholamines – must have catechol (-OH at C3 and C4) and ethylamine – isoproterenol and dobutamine are catecholamines, other two are not. XIII.ADVANTAGES OF SYNTHETIC COMPOUNDS AS THERAPEUTIC AGENTS [S13] a. Synthetic compounds increase selectivity for adrenergic receptors – alpha or beta. b. Improve bioavailability – norepi and epi have to be injected. Synthetics are orally effective. c. Prolong the half-life of effects, want the actions to last longer. Why? Lots of reasons… XIV. ENZYMATIC DEGREDATION OF SYMPATHOMIMETIC AMINES [S14] a. One reason longer half-lives are a good thing - epinephrine on left broken down by 2 different enzymes: i. MAO oxidizes the amino terminal. Once it’s oxidized, it is easily excreted from the body and has a very short half-life. MAO oxidizes and gets rid of it. ii. Catechol-O-methyltransferase (COMT) mostly in liver. Puts methyl group at C3 position of catechol, now it can be excreted. b. Both epi and norepi have very short half lives. CLASS: FUNdamentals 2 Scribe: Megan Guthman

DATE: 12.1.10 Proof: Christine Sirna PROFESSOR: Ku Sympathetic Agonists and Antagonists Part 1 Page 3 of 6 c. Isoproterenol – because of its substitution at amino terminal, it’s no loner susceptible to MAO. Isoproterenol will not be broken down by MAO, it has a longer half life. Because it’s a catechol up top, it’s still susceptible to COMT. Isoproterenol has a longer half-life than norepi and epi because MAO can’t break it down. d. Amphetamines – structure is similar, substitution at alpha carbon. Not susceptible to MAO. Anything at N (like Isoproterenol) or alpha C (like amphetamine) makes it not susceptible to MAO degradation. Amphetamine has longer half-life because it’s not susceptible to MAO. Amphetamine does not have a catechol so it is not susceptible to COMT either, stays in body longer. XV. DIRECT VS INDIRECT ACTING SYMPATHOMIMETIC AMINES [S15] a. Direct acting – norepi, isoproterenol, methoxamine b. Indirect acting – ephedrine, amphetamine, tyramine. They cause a release of norepi from the nerve terminal. They don’t directly interact with receptors. c. Notice the structures – indirect acting ones do not have a lot of hydroxyl groups. Hydroxyl is charged. More hydroxyl groups = more charged = won’t get into the blood-brain barrier so they localize in periphery. If you eliminate hydroxyl groups, it will more readily cross BBB and cause CNS effects. Indirect are lipophilic, cross lipid layers. XVI. WHAT ARE THE THERAPEUTIC ADVANTAGES OF ADMINISTERING… [S16] a. Why is indirect vs direct acting important? Systemic vs localized effects. b. Story: Teenage girl delivered baby early, has spinal tap to get C-section. Her blood pressure drops because of spinal tap – what do you do? Give agonist to pump up blood pressure – alpha agonist, constrict blood pressure to pump back up. Mother’s pressure is back to normal, but what happens to the fetus? Constricts blood vessels in umbilical cord, fetus dies. Any blood vessel with alpha receptor will constrict. Direct acting constricts everything. c. Want indirect acting to get localized effects. Umbilical cord is not innervated; it does not have sympathetic nerve terminals. Indirect acting will release norepi to mother– her sympathetic innervated body will be constricted and go back to normal, and the fetus will be left alone because unbilical cord is not innervated, does not have norepinephrine. Want localized effect and not systemic effect. d. Other problem with indirect – all it does is release norepi. Once you release all your vesicles, you don’t get an effect anymore. Direct will continue acting - as long as it’s there, it will activate. XVII. INDIRECT-ACTING SYMPATHOMIMETICS [S17] a. Indirect acting. b. Ephedrine commonly used as a nasal decongestant. Structure similar to meth. Can’t get ephedrine over the counter anymore - people abused it. Remove hydroxyl group with ether and make it meth very cheap. Big explosion in garage. XVIII. FIGURE [S18] a. Signal transduction mechanisms b. BETA receptor example: c. Agonists activate the receptor, and the receptor is coupled to G-proteins. Once activated, G-proteins activate adenylate cyclase, which converts ATP to to cyclic AMP. cAMP, a 2nd messenger, is formed, can do many different things depending on cell type. i. cAMP can activate cAMP-dependent kinase, PKA, which changes phosphorylase B to A, which can convert glycogen to glucose = glycogenolysis. A lot of glucose is produced in the liver. In skeletal muscle, we produce a lot of lactic acid. When you exercise, release lots of epi and norepi, build up lactate in the muscle. Different tissues convert to glucose or lactate all because of beta receptors and the cAMP systems. This is in the liver and muscles. ii. In fat cells (left pathway) activate lipase that converts fat to free fatty acids. d. All of these are regulated by cAMP. Receptors that are activated can do lipolysis or glycogenolysis depending on cell type, mediated by beta receptors. e. In the cardiovascular system (top left pathway), protein kinase activates different ion channels for cardiac muscle contractions – all mediated through cAMP and protein kinases. f. cAMP has short half life – enzyme phosphodiesterase (PDE) breaks it down making it inactive. If you inhibit PDE, it will prolong the actions of cAMP. g. Also feedback mechanisms (betaARK) to shut it down. System is very versatile – lots of checks and balances. h. Alpha 2 receptors have negative feedback on this. No alpha2 receptors, no feedback. If a cell expresses beta and alpha2, it has antagonism to shut down this pathway. XIX. METABOLIC EFFECTS [S19] CLASS: FUNdamentals 2 Scribe: Megan Guthman

DATE: 12.1.10 Proof: Christine Sirna PROFESSOR: Ku Sympathetic Agonists and Antagonists Part 1 Page 4 of 6 a. This slide is to summarize what the previous slide said. Metabolic effects, beta receptors and cAMP mediated glycogenolysis (glycogen to glucose) in liver while skeletal muscle builds up lactic acid. Lipolysis – the conversion of fat to free fatty acid. b. Potassium homeostatsis: i. Electrolytes are important in the body. The most important electrolytes are sodium, calcium potassium and magnesium. Potassium is important to stabilize cell membrane. A deviation in the potassium number will cause problems. In liver, alpha receptor releases potassium. In skeletal muscle, beta receptors will increase in number, causing a decrease of K+ in blood, the beta receptors uptake potassium. c. Lots of checks and balances, understand them. Good for exam/board questions. XX. FIGURE [S20] a. Alpha receptors – different from beta receptors. G-protein coupled receptor also. Uses a Gq protein, activates phospholipase C (PLC), 2nd messenger is IP3 (inositol triphospate). This mechanism is not through cAMP! i. IP3 activates calcium release, and calcium mediates a lot of effects. b. Alpha receptors also couple to diacylglyerol (DAG) and protein kinase C (PKC) [Don’t mix up PKC with cAMP dependent PKA]. PKC phosphorylates proteins, causes cellular events, cell growth, synaptic transmission. c. In disease state, something is out of whack with this cycle. Find a way to shut this down or stimulate it. d. NOTE: Phospholipase C is not the same as phospholipase A. PLA is involved with arachadonic acid, COX and LOX. Cox inhibitors are made for phospholipase A. XXI. RECEPTOR SPECIFICITY [S21] a. Specificity – agent is specific for either alpha or beta b. Selectivity – for alpha1 or alpha2. Beta1 or beta2 or beta3. c. Everything is relative. At therapeutic concentrations, dose that we give to elicit response is selective. Once concentration is increased 10 -100x more, you lose selectivity. Dose response: effective dose and concentration – why do we talk about these? If you use a high, supernormal dose, you lose selectivity. XXII. G-PROTEIN COUPLED RECEPTORS (GPCRs) [S22] a. Don’t worry about this slide, main point is that GPCRs are a superfamily, lots of different drugs for this family. All of these drugs help us, and they were discovered because of research on GPCRs. XXIII. RESPONSES TO ADRENERGIC AND CHOLINERGIC NERVE STIMULATION [S23] a. Another slide to not memorize – Main point: receptors distribute different places. In a single cell type, different receptors are expressed on that cell. One cell has many different types of receptors. b. One single cell type can have different subtypes expressed and functioning – can compete with each other. Alpha vs. beta – who wins? c. Ex: blood vessels – alpha for constricting, beta is dilation. Which dominates? Alpha always dominates, “just like the animal kingdom.” If you have both alpha and beta receptors on a cell and you give norepi or epi, get alpha constriction first. XXIV. RESPONSES TO ADRENERGIC AND CHOLINERGIC NERVE STIMULATION [S24] a. Heart has all beta1 and beta2. b. Optometry students will deal with this. c. Receptors express at different cell types and have different effects. d. Cholinergic can complicate this further – the ying to the adrenergic yang. Receptor subtypes can compete, and also cholinergic action can add effects. Very complex. XXV. AUTONOMIC CONTROL OF CARDIOVASCULAR FUNCTION [S25] a. Alpha for constrictions, Beta2 for vasodilatations, beta1 increases the force of contraction in the heart – top of slide list is easy to understand. b. Relativity issues – selectivity and potency issues i. Low dose of epi has beta effects ii. High dose of epi behaves like norepi – predominately alpha effects. These are potency issues. iii. Homeostatic control – the baroreceptor reflex - tells heart something is wrong. Brain tells heart to shut down. XXVI. FIGURE [S26] a. Receptor is in heart. Because of baroreceptor, stretch receptor in aorta tells brain that pressure is too high or low. Give constrictor (like phenylephrine), alpha receptor agonists, will increase blood pressure and peripheral resistance. Baroreceptor will activate, say pressure is too high, and activate parasympathetic to slow down heart, deactivates sympathetic. Activate alpha receptor telling blood vessel to constrict so BP initially goes up, but right away it’ll go back down because brain activates. b. Give histamine, a direct vasodilator, and BP initially drops – brain says activate sympathetic, shut down parasympathetic, to pump up blood pressure – example of the baroreceptor reflex. XXVII. BLOOD PRESSURE FIGURE [S27] CLASS: FUNdamentals 2 Scribe: Megan Guthman

DATE: 12.1.10 Proof: Christine Sirna PROFESSOR: Ku Sympathetic Agonists and Antagonists Part 1 Page 5 of 6 a. Nerve activities: i. Give phenylephrine, the sympathetic nerve shuts down, the parasympathetic (Vagus) nerve will activate.

ii. Give a direct vasodilator like histamine – activates sympathetic, shuts down parasympathetic. b. All of this happening in body continuously. XXVIII. FIGURE [S28] a. Classic example – shows the complexity of alpha and beta receptors. i. Peripheral vascular resistance – all blood vessels in the body. Controlled by both alpha1 and beta2. Normal blood pressure is 120/80 lying down. When you stand up, we maintain 120/80. When you stand up, alpha activates so gravity doesn’t pull your blood down and BP doesn’t drop. Without alpha receptors, BP would drop. ii. Taking alpha blockers/antagonists? Stand up and pressure drops. Need alpha to constrict blood vessel to keep blood moving. Alpha constricts, beta dilates. b. BP controlled by both beta1 and alpha1. c. Heat rate is controlled by beta1 and the baroreceptor reflex. d. Give norepinephrine – activates alpha1, alpha2, and beta1. Peripheral vascular resistance will go up right away because it activates alpha1 agonists. Because we dilated alpha1, diastolic pressure goes up. Also activate beta1 so systolic goes up (yellow line is mean BP). If you activate beta1, heart rate should go up. But heart rate drops because of baroreceptor reflex because pressure is too high. e. Give epinephrine at low dose: activates primarily beta receptors. At high doses (30-100 micrograms/min), behaves like norepi. Predominant beta effect – vessels dilate, resistance decreases, diastolic decreases. Systolic goes up because of beta1. Because pressure resistance goes down, baroreceptor reflex causes increase in heart rate. Heart rate goes up. f. Isoproterenol activates beta1 and beta2 and nothing else. Big decreases in peripheral resistance, decrease in diastolic, systolic goes up a little and mean blood pressure is no change. Heart rate really goes up. Goes up for two reasons: beta1 and baroreceptor reflex. Pressure drops so heart rate really goes up. XXIX. FIGURE [S29] a. Summarized each phase. b. Trick question: what if patient is also taking alpha blockers? What happens? What if patent is taking beta blocker? Totally different now. c. Back to previous slide – alpha effects first. Alpha blocker see not as much of a dramatic increase. Think about this! Be a thinking doctor, not a memorizing doctor. XXX. PHARMACOLOGICAL ACTIONS OF DOPAMINE [S30] a. Dopamine is precursor for norepi. Dopamine has special receptors. Involved in Parkinson’s disease. b. Cardiovascular system – D1 receptors in blood vessels cause vasodilatation. Patient in septic shock – always give agent to pump up blood pressure – give the patient dopamine, not norepi. Norepi constricts, shuts blood flow to kidney and will cause kidney failure. Dopamine will constrict blood vessels and dilate renal arteries so kidney can function normally. Always use dopamine for shock. c. This is relative - high doses will lose selectivity, activates alpha1 just like norepenphrine and cause hypertensive crisis  be careful with this! XXXI. FIGURE [S31] a. Adds dopamine to the chart to show the difference. Because of D1 receptors, decreases peripheral resistance. If you go high doses you lose this selectivity. XXXII. ADRENOCEPTORS [S32] a. Talking about drugs now. Lots of drugs listed, green and blue are prototypical drugs. i. Phenylephrine is for alpha1 agonists. ii. Chonidine is alpha 2 agonists. 1. Epinephrine, norpi, isoproterenol are listed underneath because they also activate alpha 1 and 2. They are nonselective. iii. Dobutamine for beta1, Terubtaline for beta2. Remember prototype and selectivity issues. b. Antagonists, same thing. i. Prazosin is a selective alpha1 antagonist. ii. Phentolamine blocks both alpha1 and alpha 2 = nonselective alpha blockers/antagonists. iii. Yohimbine is selective for alpha2 antagonists. iv. Beta blockers: Metoprolol is selective for beta1. Propanolol blocks both beta1 and beta2 = nonselective. c. TAKE HOME MESSAGE: Know prototype for each one and remember why we have different epi norepi and isoproterenol because they’re nonselective. The reason we put Isoproterenol is because they’re relative. If CLASS: FUNdamentals 2 Scribe: Megan Guthman

DATE: 12.1.10 Proof: Christine Sirna PROFESSOR: Ku Sympathetic Agonists and Antagonists Part 1 Page 6 of 6 you have a high enough dose of isoproterenol, you will elicit alpha response. But Isoproterenol is predominantly a beta agonist. [End 52:33 mins]