Cholinergics-1

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Pharmacology

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Cholinergics-1 : 

Cholinergics-1 Dr.S.P.Dhanya Govt TDMCA

Autonomic Nervous System : 

Autonomic Nervous System

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Preganglionic Postganlionic

Transmitters : 

Acetylcholine: ALL preganglionic neurons ALL parasympathetic postganglionic neurons Sympathetic neurons-Sweat glands Somatic motor neuron Norepinephrine (= Noradrenaline): MOST sympathetic postganglionic neurons Exception: Renal arteries (Dopamine) Epinephrine (= Adrenaline): Adrenal medulla upon sympathetic impulses Transmitters

Slide 7: 

Action Potential Na+ Ca2+ ACh Acetylcholinesterase Na+ Parasympathetic Ganglionic Synapse Preganglionic neuron Postganglionic neuron Receptor

Slide 9: 

(-) Vesamicol (-) Botulinum α Bungarotoxin (-) Aminoglycoside (-) Local anaesthetics (-) Anticholinesterases (-) Receptor blockers

Cholinesterases : 

Cholinesterases

ACh receptors : 

ACh receptors Nicotinic Muscarinic nicotine muscarine

The ‘master key’ for both types of ‘lock’ : 

nicotine muscarine The ‘master key’ for both types of ‘lock’ Acknowlegement-Dr.Kumarasingam

NM receptor : 

NM receptor NN receptor

M1 : 

M1

M2 : 

M2

M3 : 

M3

M4 : 

M4 M5

Effect : 

Effect

Autonomic control of pupil : 

Autonomic control of pupil

MIOSIS : 

MIOSIS

Effects of Muscarinic Agonists : 

Effects of Muscarinic Agonists

NICOTINIC : 

NICOTINIC 1. AUTONOMIC GANGLIA Symp + Para symp stimulation( only at high doses) If ↑ dose of Ach given after atropine ↑ BP & HR 2. SKELETAL MUSCLES Contraction of fibre 3. CNS IV – no effect Direct inj into brain – complex pattern of stimulaton followed by depression

Slide 26: 

No clinical utility Ultrashort action It is easily hydrolyzed Acid in the stomach Acetylcholine esterase in blood Acetylcholine

Classification : 

Classification

DIRECTLY ACTING CHOLINERGICS : 

DIRECTLY ACTING CHOLINERGICS CHOLINE ESTERS Acetylcholine Bethanechol Carbachol Methacholine ALKALOIDS Muscarine Pilocarpine Arecoline

CHOLINE ESTERS : 

CHOLINE ESTERS All are permanently charged quaternary Ammonium compounds Poorly absorbed, all hydrolyzed in GIT , less effective orally. Poorly distributed into CNS, not active in eye after topical application. Resistant to hydrolysis by Acetylcholinesterase ---- longer DOA than Ach. More potent than ACh.

USES : 

USES BETHANECHOL    GI smooth muscle stimulant postoperative abdominal distention paralytic ileus esophageal reflux; promotes increased esophageal motility  Urinary bladder stimulant post-operative; post-partum urinary retention alternative to pilocarpine treat diminished salivation secondary e.g. to radiation

INTERACTIONS : 

INTERACTIONS Anti choline esterases potentiate Adrenaline : Physiological Antagonist

ADVERSE EFFECTS : 

ADVERSE EFFECTS

CHOLINOMIMETIC ALKALOIDS : 

CHOLINOMIMETIC ALKALOIDS PILOCARPINE Obt from leaves of Pilocarpus Microphyllus Tertiary amine  Crosses BBB Dominant – M3 & NN Too toxic for systemic use ADR – ↑ sweating, salivation & other secretions Small doses ↓ BP High doses ↑ BP

USES : 

USES 1. EYE - Penetrates cornea – Miosis, Ciliary muscle contraction, ↓IOP lasting 4 – 8 hrs 3rd line drug - Primary open angle Glaucoma S/E : Initial stinging , Painful spasm of accomodation To counteract Mydriatics Prevent adhesions of Iris with lens/ cornea by alternating with mydriatics 2. As ? SIALOGOGUE

MUSCARINE : 

MUSCARINE Obtained from poisonous mushrooms Amantia muscaria & Inocybe Has only muscarinic actions No therapeutic indications Quarternary alkaloid ↓ BBB penetration

MUSHROOM POISONING : 

MUSHROOM POISONING 3 types of mushroom poisoning MUSCARINE TYPE Inocybe Symptoms appear within an hour of eating Reversed by ATROPINE

HALLUCINOGENIC TYPE : 

HALLUCINOGENIC TYPE Muscimol & other Isoxazole compds  A muscaria Another -Psilocybin – Psilocybe mexicana activate amino acid receptors & block muscarinic receptors in brain – HALLUCINOGENIC No specific Rx. Atropine is Contraindicated

PHALLOIDIN TYPE : 

PHALLOIDIN TYPE PEPTIDE TOXINS-in A phalloides, Galerina (-) RNA & protein syn Symptoms after many hrs - due to damage : GI mucosa , Liver & Kidney Rx : Supportive measures Thioctic acid : Antidotal effect

ARECOLINE : 

ARECOLINE Betel nut Predominant M + slight N Prominent CNS effect

CEVIMELINE : 

CEVIMELINE Direct acting at M3 Lacrimal & Salivary gland epithelium Longer lasting Sialogogue action than pilocarpine ↑ lacrimal secretion in Sjogrens syndrome

INDIRECTLY ACTING PARASYMPATHATOMIMETICS : 

INDIRECTLY ACTING PARASYMPATHATOMIMETICS

ANTI CHOLINE ESTERASES : 

ANTI CHOLINE ESTERASES NATURAL Physostigmine Galantamine SYNTHETIC CARBAMATES ACRIDINE Neostigmine Tacrine Pyridostigmine Edrophonium Donepezil Rivastigmine REVERSIBLE

IRREVERSIBLE : 

IRREVERSIBLE Organophosphates Ecothiophate Isoflurophate Paraoxon Parathion Malathion Diazinon NERVE GASES Tabun , Sarin , soman CARBAMATES Carbaryl Propoxur

Thank You : 

Thank You

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