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CHOLINERGIC TRANSMISSION

CHOLINERGIC TRANSMISSION. A:- Precursor - Choline B :- Enzyme- Synthesizing - Choline Acetylase Degrading - A cetycholine Esterase (TRUE) - Butyrylcholine Esterase (PSEUDO) C :- 300,000 vesicles

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CHOLINERGIC TRANSMISSION

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  1. CHOLINERGIC TRANSMISSION A:- Precursor - Choline B :- Enzyme- Synthesizing - Choline Acetylase Degrading - Acetycholine Esterase (TRUE) - Butyrylcholine Esterase(PSEUDO) C :- 300,000 vesicles Quantum - 0.1 to 0.3 mv - 1mepp/sec

  2. CHOLINERGIC TRANSMISSION (CONTD.) RECEPTORS N - Ligand gated ion channels Nn& Nm M - Through G- protein signalling systems M1 – Stomach Glands - Release of hist. - Secretion of acid M2 – (i) Myocardium - ↓ generation of impulses –SA - ↓ conduction of impulse – AV - ↓ contractility –Atria & Ventricle

  3. CHOLINERGIC TRANSMISSION (CONTD.) (ii) Pre-synaptic ↓ Ach from cholinergic neurons ↓ NA Postgang. sym. Neurones M3 - Smooth muscle – Contraction - Exocrine glands – ↑ secretion - Vascular Endothelium – ↑ NO secretion

  4. CLASSIFICATION CHOLINE ESTERS - Acetylcholine - Methacholine - Carbachol - Bethanechol - Cevimeline NATURAL ALKALOID - Muscarine - Pilocarpine - Arecoline - Nicotine

  5. ANTI- CHOLINESTERASES A) Reversible - Physostigmine - Neostigmine - Pyridostigmine - Edrophonium - Rivastigmine - Donepezil

  6. ANTI- CHOLINESTERASES(contd.) B) Irreversible - Parathion (agricultural insecticides) - Malathion - Diazinon (Household) - Propoxur - Tabun - Sarin (Chemical warfare) - Soman

  7. PHARMACOLOGICAL ACTIONS • CVS (M2) a) Heart :- ↓ G/C /C in Myocardium (PR ↑ – AV) b) Blood Vessel(M3) Dilatation – ↓ BP → Reflex tachycardia innervation is only on face to neck 2) Exocrine glands (M3) Sweating > Salivation > Lacrimation = TBT secretion >> Gastric secretion

  8. PHARMACOLOGICAL ACTIONS(contd.) 3) Smooth Muscle a) G.I. – ↑ Tone & Peristalsis b) Urinary System – ↑ Tone , Voiding c) Bronchi – ↑ Tone (Bronchial Asthma) 4) Eye- Cont. of circular mus. of iris →Miosis. - Cont. of ciliary mus.→ thickeningof lens

  9. PHARMACOLOGICAL ACTIONS(contd.) 5) Skeletal muscles (NM) Twitching & fasciculation 6) Autonomic ganglia(Nn) Both Ad & Ch- unpredictable 7) CNS (M+N) Rapid destruction + min. entry →unpredictable response. 8) Stomach (M1) – ↑ acid+ Pepsin

  10. USES OF CHOLINE ESTERS 1) Cardiac – PSVT – Methacholine 2) Intestinal – Paralytic ileus ,Megacolon (carbachol/ bethanechol) 3) Urinary - Retention of urine (carbachol /bethanechol) 4) Lacrimal Secretion & Sialogogue – Cevimeline

  11. CHOLINOMIMETIC ALKALOIDS Pilocarpine:- - As eye drops – Miosis - Ch. simple glaucoma – Drops Vs. Ocusert - To prevent and break adhesions between iris / lens and iris /cornea Muscarine, Arecolineand Nicotine

  12. CHOLINESTERASE INHIBITORS Reversible Physostigmine(Eserine) :- -Natural ,lipid soluble compound -Rapidly absorbed and crosses BBB – CNS effects -Poisoning with Atropine , Phenothiazines& Tricyclic Antidepressants

  13. CHOLINESTERASE INHIBITORS(contd.) Neostigmine – -Synthetic, much less lipid soluble -Does not cross BBB – No central effects - ACh action on NMJ – Myasthenia gravis - If intolerable M effects – Atropine -Steroids – ↓ production of Nm antibodies -Thymectomy • Also in paralytic ileus & bladder atony.

  14. CHOLINESTERASE INHIBITORS (contd.) Pyridostigmine- Less potent , Long duration Edrophonium - Very short duration - To identify between “Myasthenic” and “Cholinergic” crisis Rivastigmine Newer agents, AD, Long acting, Donepezil Well tolerated

  15. OTHER USES :- a) Cobra bite –venom b) Decurarisationafter G.A c) Curare & other poisonings d) Edrophonium(PSVT)

  16. ChEINHIBITORS – IRREVERSIBLE High efficacy ------ Toxicity (cross BBB) High lipid soluble – Rapid absorption from all routes Poisoning occurrence - Accidental , suicidal, homicidal

  17. Muscarinic Effects - Inhalation / ingestion/ vapours (Eye) Miosis, lacrimation - ↑ secretion – Dehydration - Fall in BP – Reflex Tachycardia - ↑ dose –VMC at medulla (Bradycardia) - ↑ contraction of smooth muscle - Ataxia, convulsion , coma , death due to Respiratory Failure

  18. TREATMENT • Change clothes. Wash skin , eyes. Gastric lavage. • Fresh air, Patent airway, PPR, Hydration • Maintenance of BP- vasopressor agent • CONVULSION – Diazepam i.v Atropine Enzyme Reactivator – Oximes DAM, Pralidoxime, Obidoxime

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