Question

Why are the effects of Acetylcholinesterase Inhibitors effectively the same as the effects of Ach and direct cholinergic agents? Why do anticholineric/cholinergic receptor blocking drugs like atropine (muscarinic antagonist) exhibit effects that are opposite those of Ach, Direct Cholinegic Drugs, and Indirect Cholinergic Drugs (i.e., acetylcholinesterase inhibitors)? Direct vs Indirect-Acting cholinergics ? Direct vs Indirect-Acting adrenergics? Know which receptor is associated with which second messenger system, and whether that messenger system is activated or inhibited by an agonist or antagonist. For example, activation of beta-adrenergic receptors activates adenylyl cyclase and increases cAMP. Blockade of beta receptors prevents adenylyl cyclase activation. What about all the other adrenergic and cholinergic receptors?

Answer 1

• Acetylcholine (Ach) is a neurotransmitter which is a chemical released by a neuron that sends signal to other neuron through synapse. When activated it causes the contraction of muscles and activates glandular functions in the endocrine system.
• Acetylcholinerase inhibitors are the drugs that inhibit the enzyme -acetylcholinesterase which is involved in the termination of impulse transmission by rapid hydrolysis of acetylcholine into choline and acetic acid. So, these drugs are used to increase the levels of acetylcholine and activation of muscarinic or nicotinic receptors and the effects produced by these drugs are similar to Acetylcholine. examples Donepezil, Rivastigmine, galantamine.
• Direct cholinergic drugs binds directly to muscarnic or nicotinic Ach receptors. These drugs are commonly used in opthalmology to induce miosis .
• acetylcholinesterase inhibitors and direct ach agonists are used to increase the neurotransmitter acetylcholine so the effects produced by these drugs are similar to acetylcholine .