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how can you classify cholinoceptor stimulants?
either through spectrum of action or mode of action
two types of cholinoceptors
muscarinic and nicotinic
Site of Muscarinic Receptor based on subtypes; Generalization on postreceptor mechanism
- M1 Nerves; M2 heart nerves and smooth muscle; M3 Glands, smooth muscle, and endothelium, M4 and M5 = CNS
- Odd (135) IP3, DAG cascade via Gq/11
- Even (2,4) via cAMP prod. inhibition and activation of K+ ch via Gi/o
between Muscarinic and Nicotinic which stimulates autonomic neuroeffector junction, autonomic ganglia and skeletal NMJ?
muscarinic = neuroeffector junction; Nicotinic = ganglia and NMJ
how can you remember whether the site is muscarinic or nicotinic?
- nicotinic - ion type of signalling = fast = muscle and nerves (postganglionic cells/dendrites)
- muscarinic = transmembrane signalling = slow and long lasting = nerves, heart, glands (m1,2,3)
what do you mean by direct-acting cholinomimetic agents and indirect-acting?
- Direct = act on receptor itself
- Indirect = inhibit metab/termination of Ach via AcHase increasing concentration amplifying Ach effects
- other drugs like neostigmine has both direct and indirect MOA
relate the structure of esters of choline with its distribution and potency
- 1. esters of choline has permanently charged quarternary ammonium group rendering them relatively insoluble to lipids --> hydrophilic --> can't pass CNS barrier
- 2. high susceptibility with hydrolysis requires greater concentration for a a brief time. other more complex structure derived from Ach are more resistant to hydrolysis like Metacholine, Carbamic acid and Bethanechol
- 3. Metacholine and Bethanecol contains B-methyl group reducing its potency on nicotinic receptor
to increase tertiary amine clearance, urine should be acidified? or alkalinized?
effects of muscarinic agonists to eyes.. explain why it is indicated in patients with high ocular pressure..
M3 of circular muscle of iris (contraction) and ciliary muscle contraction. contraction of ciliary muscle pulls back iris away from anterior chamber and opens the trabecular meshwork at the base of ciliary muscle, both leading to aqueous humor outflow into the canal of schlemm draining the anterior chamber decreasing ocular pressure