Cholinergic Agonists

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Which of the following statements about carbachol is true?

It is primarily used in the treatment of glaucoma.

It has a short duration of action.

It provides miosis for eye surgery. (correct)

It is commonly used due to its receptor selectivity.

Why is pilocarpine considered less potent compared to ACh and its derivatives?

It can penetrate the CNS at therapeutic doses. (correct)

It is not stable to hydrolysis by AChE.

It has a quicker onset of action.

It is a quaternary amine.

What effect does pilocarpine have when applied topically to the eye?

Increased intraocular pressure

Rapid miosis (correct)

Relaxation of the ciliary muscle

Dilation of the pupil

Why has the use of pilocarpine for stimulating secretions been limited?

Its lack of potency Signup and view all the answers

In which condition is pilocarpine the drug of choice for emergency lowering of intraocular pressure?

Glaucoma Signup and view all the answers

Why is carbachol rarely used despite its high potency?

It is a quaternary amine. Signup and view all the answers

What are the two classes of postsynaptic cholinergic receptors?

Muscarinic and nicotinic Signup and view all the answers

What enzyme is responsible for cleaving acetylcholine in the synaptic cleft?

Acetylcholinesterase (AChE) Signup and view all the answers

What happens when acetylcholine binds to a receptor on a cell?

It initiates a nerve impulse in a postganglionic fiber Signup and view all the answers

What is the main function of cholinergic receptors on effector organs?

To activate specific enzymes Signup and view all the answers

How is choline recycled in the cholinergic neuron?

By being transported back into the neuron with a high-affinity uptake system Signup and view all the answers

Which molecules mediate the activation of specific enzymes in effector cells after binding of ACh to a receptor?

Second messenger molecules Signup and view all the answers

Which enzyme specifically cleaves acetylcholine into acetate and choline?

Acetylcholinesterase Signup and view all the answers

What is the mechanism of action of reversible anticholinesterase agents?

Inhibiting the breakdown of acetylcholine Signup and view all the answers

Which reversible AChE inhibitor has a short duration of action due to rapid renal elimination?

Edrophonium Signup and view all the answers

Where does acetylcholinesterase (AChE) act within the nerve terminal?

Both pre- and postsynaptic membranes Signup and view all the answers

What is the main function of reversible anticholinesterase agents?

Preventing the breakdown of acetylcholine Signup and view all the answers

Which type of receptors can be affected by reversible AChE inhibitors?

Both muscarinic and nicotinic receptors Signup and view all the answers

What is the rate-limiting step in acetylcholine synthesis at cholinergic neurons?

Uptake of choline Signup and view all the answers

Which enzyme catalyzes the reaction of choline with acetyl coenzyme A to form acetylcholine in the cytosol?

Choline acetyltransferase Signup and view all the answers

What is the role of choline in acetylcholine synthesis at cholinergic neurons?

Choline combines with acetyl coenzyme A to form acetylcholine Signup and view all the answers

Which drug can inhibit the carrier system responsible for transporting choline into the cytoplasm of cholinergic neurons?

Hemicholinium Signup and view all the answers

What is the fate of acetylcholine after it binds to the receptor at cholinergic neurons?

Degradation in the synaptic cleft Signup and view all the answers

Apart from sweat glands, where else does the postganglionic sympathetic division of sweat glands use ACh?

Muscles of somatic system Signup and view all the answers

What is the intermediate duration of action for neostigmine?

30 minutes to 2 hours Signup and view all the answers

Which of the following is a therapeutic use of neostigmine?

Managing symptoms of myasthenia gravis Signup and view all the answers

What adverse effect is NOT associated with neostigmine use?

CNS side effects Signup and view all the answers

Why is neostigmine contraindicated when intestinal or urinary bladder obstruction is present?

It stimulates the affected muscles, worsening the obstruction Signup and view all the answers

Which cholinesterase inhibitor has a duration of action longer than neostigmine but still intermediate?

Pyridostigmine Signup and view all the answers

What is the main deficiency in patients with Alzheimer's disease that leads to the use of cholinesterase inhibitors like tacrine, donepezil, rivastigmine, and galantamine?

Acetylcholine (ACh) Signup and view all the answers

What is the primary adverse effect associated with reversible anticholinesterase agents such as donepezil, rivastigmine, and galantamine?

GI distress Signup and view all the answers

What is the mechanism of action of irreversible anticholinesterase agents like organophosphates?

Covalent binding to AChE Signup and view all the answers

Which compound is an irreversible anticholinesterase agent that forms a covalent bond at the active site of AChE?

Echothiophate Signup and view all the answers

What is required for the restoration of acetylcholinesterase (AChE) activity after irreversible inhibition by organophosphates?

Synthesis of new enzyme molecules Signup and view all the answers

Which of the following is a true statement about the mechanism of action of echothiophate?

It permanently inactivates AChE via covalent binding Signup and view all the answers

Which organophosphate compound is used as an insecticide and can bind covalently to AChE?

Parathion Signup and view all the answers

What is the major disadvantage of tacrine compared to other anticholinesterases?

Hepatotoxicity Signup and view all the answers

Which anticholinesterase agent permanently inactivates AChE by forming a covalent bond at its active site?

Echothiophate Signup and view all the answers

Why were many irreversible organophosphate anticholinesterases initially developed by the military?

For nerve agent use in warfare Signup and view all the answers

What happens to the AChE enzyme after it is covalently modified by echothiophate?

It slowly releases ethyl groups Signup and view all the answers

What is the primary toxic manifestation of toxicity with irreversible AChE inhibitors like organophosphates?

Nicotinic and muscarinic signs Signup and view all the answers

Why is pralidoxime (2-PAM) ineffective in treating the central nervous system (CNS) effects of organophosphates?

It cannot penetrate the CNS Signup and view all the answers

What effect can pralidoxime have on peripheral effects of organophosphates if administered before aging of the alkylated enzyme occurs?

Reverses both muscarinic and nicotinic peripheral effects Signup and view all the answers

Why is pralidoxime less effective with newer nerve agents that lead to aging of the enzyme complex within seconds?

The enzyme aging process occurs too quickly Signup and view all the answers

In the context of anticholinesterase agents, what does pralidoxime essentially displace on the enzyme?

Phosphate group of organophosphate Signup and view all the answers

What is the limitation of pralidoxime in reversing the effects of organophosphates if aging of the alkylated enzyme has already occurred?

It cannot reverse nicotinic effects fully Signup and view all the answers

Cholinergic Agonists

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Questions and Answers

Which of the following statements about carbachol is true?

Why is pilocarpine considered less potent compared to ACh and its derivatives?

What effect does pilocarpine have when applied topically to the eye?

Why has the use of pilocarpine for stimulating secretions been limited?

In which condition is pilocarpine the drug of choice for emergency lowering of intraocular pressure?

Why is carbachol rarely used despite its high potency?

What are the two classes of postsynaptic cholinergic receptors?

What enzyme is responsible for cleaving acetylcholine in the synaptic cleft?

What happens when acetylcholine binds to a receptor on a cell?

What is the main function of cholinergic receptors on effector organs?

How is choline recycled in the cholinergic neuron?

Which molecules mediate the activation of specific enzymes in effector cells after binding of ACh to a receptor?

Which enzyme specifically cleaves acetylcholine into acetate and choline?

What is the mechanism of action of reversible anticholinesterase agents?

Which reversible AChE inhibitor has a short duration of action due to rapid renal elimination?

Where does acetylcholinesterase (AChE) act within the nerve terminal?

What is the main function of reversible anticholinesterase agents?

Which type of receptors can be affected by reversible AChE inhibitors?

What is the rate-limiting step in acetylcholine synthesis at cholinergic neurons?

Which enzyme catalyzes the reaction of choline with acetyl coenzyme A to form acetylcholine in the cytosol?

What is the role of choline in acetylcholine synthesis at cholinergic neurons?

Which drug can inhibit the carrier system responsible for transporting choline into the cytoplasm of cholinergic neurons?

What is the fate of acetylcholine after it binds to the receptor at cholinergic neurons?

Apart from sweat glands, where else does the postganglionic sympathetic division of sweat glands use ACh?

What is the intermediate duration of action for neostigmine?

Which of the following is a therapeutic use of neostigmine?

What adverse effect is NOT associated with neostigmine use?

Why is neostigmine contraindicated when intestinal or urinary bladder obstruction is present?

Which cholinesterase inhibitor has a duration of action longer than neostigmine but still intermediate?

What is the main deficiency in patients with Alzheimer's disease that leads to the use of cholinesterase inhibitors like tacrine, donepezil, rivastigmine, and galantamine?

What is the primary adverse effect associated with reversible anticholinesterase agents such as donepezil, rivastigmine, and galantamine?

What is the mechanism of action of irreversible anticholinesterase agents like organophosphates?

Which compound is an irreversible anticholinesterase agent that forms a covalent bond at the active site of AChE?

What is required for the restoration of acetylcholinesterase (AChE) activity after irreversible inhibition by organophosphates?

Which of the following is a true statement about the mechanism of action of echothiophate?

Which organophosphate compound is used as an insecticide and can bind covalently to AChE?

What is the major disadvantage of tacrine compared to other anticholinesterases?

Which anticholinesterase agent permanently inactivates AChE by forming a covalent bond at its active site?

Why were many irreversible organophosphate anticholinesterases initially developed by the military?

What happens to the AChE enzyme after it is covalently modified by echothiophate?

What is the primary toxic manifestation of toxicity with irreversible AChE inhibitors like organophosphates?

Why is pralidoxime (2-PAM) ineffective in treating the central nervous system (CNS) effects of organophosphates?

What effect can pralidoxime have on peripheral effects of organophosphates if administered before aging of the alkylated enzyme occurs?

Why is pralidoxime less effective with newer nerve agents that lead to aging of the enzyme complex within seconds?

In the context of anticholinesterase agents, what does pralidoxime essentially displace on the enzyme?

What is the limitation of pralidoxime in reversing the effects of organophosphates if aging of the alkylated enzyme has already occurred?

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