Lecture 4 Cholinergics & Adrenergics Flashcards
Cholinergic and Adrenergic Drugs
- Drugs that effect the ANS are divided into 2 subgroups - Are classified based on the type of neuron involved - These drugs either stimulate or block neurons of ANS
Cholinergic Drugs
- Act on receptors that are activated by Acetylcholine
Adrenergic Drugs
- Act on receptors that are stimulated by norepinephrine or epinephrine
Sympathomimetic
- Drugs that act directly on receptors
Adrenergic Drugs and NE (norepinephrine), EPI (Epinephrine)
- Drugs that block the action ro by interrupting the release of NE or EPI
Adrenergic Neurons
- Release NE as a Neurotransmitter and are found in the CNS also in the Sympathetic nervous system
Synthesis of NE (Norepinephrine):
- Tyrosine is transported by NA linked into the adrenergic neuron - Hydroxylated into DOPA (dihydroxyphenylalanine) by tyrosine hydroxylase which is the rate-limiting step in the formation of NE - DOPA is decarboxylated to form dopamine - Dopamine is transported into synaptic vesicles - Dopamine is hydroxylated into NE by dopamine hydroxylase - In the adrenal medulla NE is converted into EPI
Adrenergic
- Upon stimulation the adrenal medulla releases 85% EPI and 15% NE - Binding by receptor: NE will bind post and presynaptic - Removal of NE: catechol O methyltransferase (COMT) will metabolize NE or by reuptake which can be inhibited by TCAs or Cocaine - MAO will deactivate NE - inactive products of NE are excreted in the urine
Adrenergic Alpha 1
- Vasoconstriction, increased peripheral resistance, increased blood pressure, mydriasis, increased closure of internal sphincter of the bladder
Adrenergic Alpha 2
- Inhibition of NE release, inhibition of insulin release
Adrenergic Beta 1
- Tachycardia, increased lipolysis, increased myocardial contractility
Adrenergic Beta 2
- Vasodilation, slightly decreased peripheral resistance, bronchodilation, increased muscles and liver glycogenolysis, increased release of glucagon, relaxed uterine smooth muscles
Adrenergic Alpha 1 Agonist
- EPI, NE, DA, Dobutamine, Phenlephrine
Adrenergic Alpha 1 Blocker
- Phenotolamine, Prazosin
Adrenergic Beta 1 Agonist
- EPI, NE, DA, Dobutamine, Isoproterenol
Adrenergic Beta 1 Blocker
- Propranolol, Metoprolol, Atenolol
Adrenergic Beta 2 Agonist
- EPI, DA, Dobutamine, Isoproterenol, Albuterol
Adrenergic Beta 2 Blocker
- Propranolol
Clinical Uses - Epinephrine
- Hypotension - Bronchospasm - Nasal Decongestant - Ophthalmic
Clinical Uses - Dopamine
- Decompensated Congestive Heart Failure - Hypotension - Renal Perfusion
Clinical Uses - Dobutamine
- Congestive Heart Failure
Clinical Uses - Phentolamine
- Coronary Artery Disease - Peptic Ulcer
Clinical Uses - Phenylephrine
- Nasal Decongestant
Clinical Uses - Prazosin
- Hypertension - Benign Prostatic Hyperplasia
Clinical Uses - Clonodine
- Antihypertensive - Opiod Withdrawal - Antidiarrheal in diabetic patients W/Autonomic Neuropathy
Clinical Uses - Metoprolol
- Arrhythmias - Chronic CHF
Clinical Uses - Propranolol
- Ischemic Heart Disease - Hypertension - Arrhythmias - Essential Tremors - Stage Fright - Migraine Precention
Clinical Uses - Alcuterol
- Bronchospasm - Asthma - Bronchitis - COPD
Clinical Uses - Indirect Sympathomimetic - Cocaine
- Potentiates NE by blocking repute of catecholamines - Clinical use – Surface anesthesia
Clinical Uses - Indirect Sympathomimetic - Ephidrine
- Stimulates release of NE from sympathetic neurons - Clinical use – nasal decongestion, orthostatic hypotension, promotes urinary continence
Clinical Uses - Indirect Sympathomimetic - Amphetamine
- After presynaptic uptake this agent causes the release of endogenous NE - Clinical use – ADHD, Obesity, Narcolepsy
Cholinergic Neuron - AcH
- AcH released from the synaptic vesicles diffuses across the synaptic space and binds to either postsynaptic receptors on the target cell or to presynaptic receptors in the membrane of the neuron that released the AcH
Cholinergic Neuron - Degradation of Acetylcholine
- Occurs in the synaptic cleft by acetylcholinesterase
Cholinergic Neuron - Recycling of Choline
- Occurs by a uptake system that transport the molecule back into the neuron, is acetylated and stored until released by action potential
2 types of Cholinoceptors
- Muscarinic Receptors - Nicotine Receptors
Cholinergic Neuron - Muscarinic Receptors
- Bind AcH and muscarine (poisonous mushrooms) weak affinity for nicotine - Found on ganglia of the PNS and autonomic effector organs (heart, smooth muscles, brain) also on gastric parietal cells
Cholinergic Neuron - Nicotine
- Depolarizes ganglia, first effects are stimulating followed by paralysis of all ganglia - First effects increase blood pressure and cardiac rate due to release of transmitter for adrenergic terminals and from the adrenal medulla - Increase peristalsis and secretions
Nicotine Stimulation - Release of Glutamate
- A neurotransmitter involved in learning and memory - Glutamate enhances the connections between sets of neurons. These stronger connections mat be the physical basis of what we know as memory - When you use nicotine, glutamate may create a memory loop of the good feelings you get and further drive the desire to use nicotine - Nicotine also increases the level of other neurotransmitters and chemicals that modulate how your brain works. For example, your brain makes more endorphins in response to nicotine
Nicotine stimulation - Endorphins
- Are small proteins that are often called the body’s natural pain killer - It turns out that the chemical structure of endorphins is very similar to that of heavy-duty synthetic painkillers like morphine - Can lead to feelings of euphoria - “runners high” = endorphin rush, this outpouring of chemicals gives you a mental edge to finish the race while temporarily masking the nagging pains you might otherwise feel
Chantix Anti-smoking Med
- Binds to nicotine receptors and blocks them so that nicotine can no longer activate those receptors - This means that when someone is trying to quit and they lapse and smoke they probably won’t get much satisfaction from it and will be less likely to smoke another
Chantix - Secondary mechanism
- It triggers some of the same effects that nicotine has (an “agonist” effect) - This includes a small release of dopamine, the reward neurotransmitter in the brain - In this way chantix dampens down nicotine withdrawal symptoms and cravings
Cholinergic Neuron - Inhibition of Acetylcholinesterase
- Inhibition of Aceytlcholinesterase at the skeletal neuromuscular junction causes the accumulation of acetylcholine and ultimately results in paralysis of skeletal muscles