Cholinomimetic Activators & Effects

by Pravin Shukle, MD

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    00:01 Hi, welcome to pharmacology by Lecturio. We're going to continue our discovery of the autonomic nervous system and the drugs that we use to control various aspects of it. I'm Dr.Pravin Shukle. Let's start by taking a look at all of the direct activators of the cholinergic system. What we mention before in a previous lecture was that there were two types of cholinergic receptors. The muscarinic receptors and the nicotinic receptors. Now in order to have activity at the muscarinic or nicotinic receptors, we sometimes use choline esters to activate them. Acetylcholine, methacholine and carbachol will act at both muscarinic and cholinergic receptors. So these three drugs are drugs worth remembering but remember that they are not necessarily specific between the two. The alkaloids, in particular pilocarpine is a very specific muscarinic cholinergic agent. Obviously muscarine, which is a chemical that we use sometimes is a muscarinic agent. And nicotine which is available in any cigarette that you want to smoke is active at the nicotinic receptor which is where they both got their names. So now, we have acetylcholine in the synaptic cleft. There is one of two things that can happen with acetylcholine. The first thing is that it will get broken down by acetylcholinesterase into choline and acetate. That's what we call metabolism of acetylcholine. The second thing that can happen is it will actually act on the cholinergic receptor. Now, if you activate acetylcholinesterase or give it a chance to work the activity of the cholinergic receptor is going to be reduced. So acetylcholinesterase stimulators will actually reduce the effect of that particular choline postsynaptic agent. Let's take a look at indirect activators. So edrophonium is a very short acting acetylcholinesterase inhibitor. Organophosphates are intermediate acting so they act for about 2 to 8 hours. Malathion, parathion or pesticides and sarin is a terrorist drug if you will, that was used in the 1995 Tokyo attack. So these are acetylcholinesterase inhibitors which means that the amount of acetylcholine is increased in the synaptic cleft because you are inhibiting the breakdown. Carbamates are long acting acetylcholinesterase inhibitors.

    02:41 They will act anywhere in between 5 and 21 days. So there is neostigmine and physostigmine. And these are often used in the treatment of a disease called myasthenia gravis. We are going to talk about that in a later lecture.

    About the Lecture

    The lecture Cholinomimetic Activators & Effects by Pravin Shukle, MD is from the course ANS - Pharmacology.

    Included Quiz Questions

    1. Pilocarpine
    2. Acetylcholine
    3. Bethanechol
    4. Carbachol
    5. Methacoline
    1. Neostigmine
    2. Malathion
    3. Parathion
    4. Edrophonium
    5. Sarin
    1. Muscle relaxant
    2. Pesticide
    3. Diagnosis of neuromuscular junction disease
    4. Chemical weapon
    5. Treatment for myasthenia gravis

    Author of lecture Cholinomimetic Activators & Effects

     Pravin Shukle, MD

    Pravin Shukle, MD

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