Test 2 Lecture 5 Flashcards
What are the 2 overall types of cholinergic receptors?
How many different ones are there?
G protein-linked (muscarinic receptors) and ligand-gated ion channels (nicotinic
receptors) .
- 5 (3 w/known fcn)
Where are muscarinic receptors found?
Smooth muscle, cardiac muscles, most
exocrine glands, sweat glands, in blood vessels of the major vascular beds, and at cortical and subcortical sites in the CNS
The nicotinic receptors are pentomeric (five) transmembrane polypeptides, the subunits of which form a selective channel permeable to what 2 ions?
Na+ and K+
Where are nicotinic receptors found?
Plasma membranes of parasympathetic and sympathetic postganglionic cells in the autonomic ganglia (Nn-neuronal) and on the membranes of SkM (Nm-muscle). Neuronal nicotinic receptors (Nn) are also expressed in cortical and subcortical nuclei in the brain.
Nicotinic receptors are present on postganglionic cells of both the symp and parasymp nervous systems. What does this mean that nicotinic agonists can do, physiologically?
Nicotinic agonists can activate both the sympathetic and parasympathetic systems simultaneously.
What are the effects of stimulating muscarinic receptors?
- Activates myenteric plexus
- Decreases HR (*M2)
- Contracts circular ciliary m.
- Bronchoconstriction
- Contracts GI smooth m.
- Contracts bladder detrusor m. (micturition)
- Stimulates secretions from GI tract, eccrine sweat glands, tear glands, salivary glands
Generally, what type of drug is succinylcholine?
Muscle relaxant (Blocks Nm–see future lectures)
What’s another name for muscarinic agonists?
Parasympathomimetics
What receptor types does ACh bind?
Why doesn’t it have a therapeutic use?
- Nitotinic and muscarinic
- Because it’s rapidly hydrolyzed by plasma and actylcholinergic esterases
What classification of drug is methacholine? What are its effects? Indications? Toxicity? Contraindications?
- Quaternary nitrogen analogue (hydrolyzed more slowly than ACh)
- Effects: Primarily muscarinic
- Indications: to dx bronchial hyperactivity in pts suspected of having asthma
- Tox: bronchiolar constriction
- Contra: in pts given beta-blockers (beta-blockade)
What classification of drug is carbachol? What are its effects? Indications? Toxicity? (No contraindications)
- Quaternary nitrogen analogue (resistant to hydrolysis by ACh-esterase
- Effects: Both muscarinic and nicotinic
- Indications: topical miotic agent for ocular surgery and glaucoma
- Tox: excessive muscarinic activation
i.e., bronchoconstriction, reduced cardiac
conduction
What classification of drug is bethanechol? What are its effects? Indications? Toxicity? Contraindications?
- Quaternary nitrogen analogue (hydrolyzed more slowly than ACh)
- Effects: Muscarinic only (*less CV effects–less M2 activity)
- Indications: post-op urinary retention neurogenic bladder atony
- Tox: bradycardia (even w/less M2 activity), bronchoconstriction
- Contra: asthma, peptic ulcer (stomach secretions can cause ulcers), bradycardia
What drug class is muscarine in? What receptor does muscarine bind? Why isn't it used clinically?
How is muscarine poisoning treated?
- Tertiary amine muscarinic agonists (has quaternary nitrogen structure)
- Muscarinic
- Too potent; no ester moiety so resistant to breakdown
Tx w/atropine, a muscarinic antagonist
What classification of drug is pilocarpine? (Does it cross BBB? 1/2-life?) What are its effects? Indications? Toxicity? (No contraindications)
- Non-selective muscarinic receptor agonist (crosses BBB; 1/2-life ~1 hr)
- Effects: Activates all muscarinic receptors
- Indications: dry mouth and neck from radiotherapy, also open angle glaucoma, acute and chronic angle-closure glaucoma
- Tox: excess muscarnic activation (slowed AV conduction), hypotension, excessive salivation and bronchoconstriction
What’s the difference b/w open- and closed-angle glaucoma?
Open-angle glaucoma (chronic glaucoma) is what the majority of glaucoma pts suffer from. Aqueous fluid does not drain well out of the eye, potentially causing dmg to the optic n.
Closed angle glaucoma (acute glaucoma) is an emergency. This occurs when the iris bows forward and completely blocks fluid access to the trabecular meshwork. The pressure builds up in a positive feedback loop, the patient has excruciating eye pain, and vision is lost quickly. (Use pilocarpine to help)
