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Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
Autacoids (ii)
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Autacoids (ii)

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  • 1. AUTACOIDS (II) 5-Hydroxytryptamine (5-HT) SEROTONIN
  • 2. • It is widely distributed in plants and animals. Highest concentration in mammals is found in the pineal gland, acting as a precursor for melatonin. It is synthesized from the amino acid tryptophan and acts on several types of receptors.
  • 3. Sources:Platelets Enterochromaffin cells (Intestines) CNS:- Tryptaminergic Neurons
  • 4. Physiological Functions 1. Neurotransmitter (CNS) 2. 5-HT released from platelets may account for vasospasm that accompanies certain diseases like Raynaud’s. 3. Regulation of intestinal activity. 4. Synthesis of Melatonin in Pineal body.
  • 5. VASCULAR INJURY 5-HT2A Accelerated Platelet Aggregation Initial Platelet aggregation Release of 5-HT 5-HT1 Release of EDRF (Vasodilatation) 5-HT2A Thrombus Heamostasis Vascular occlusion Vasoconstriction 5-HT EFFECTS ON BLOOD VESSELS AND HAEMOSTASIS
  • 6. • 5-HT causes constriction of renal, splanchnic, meningeal, and pulmonary arteries and veins and venules, but dilatation of the blood vessels of skeletal musles, coronaries, and skin capillaries. It has weak direct inochronotropic effect on the myocardium. It also stimulates smooth muscles, especially of the intestines.
  • 7. • Serotonin is widely distributed in the CNS, serving as a neurotransmitter. Altered functions may be responsible for disturbances in sleep, mood, sexual behavior, motor activity, pain perception, migraine, temperature regulation, endocrine control, psychiatric disorders and extrapyramidal activity.
  • 8. PHARMACOLOGICAL ACTIONS I. CARDIOVASCULAR SYSTEM 1. Blood Pressure i. Fall (Bezold Jarisch Reflex) stimulation of sensory receptors in heart. ii. Pressor phase:- Due to vasoconstriction (Peripheral vessels) and release of NE.
  • 9. iii. Prolonged Fall, with in 1 to 2 minutes of I/V injection. Dilatation of B.V. in skeletal muscles.
  • 10. FALL FALL RISE
  • 11. 2. Capillary Permeability:- Nil 3. Blood vessels and Hemostasis:- See Fig 4. Heart:- +ve Inotropic, +ve Chronotropic II. SMOOTH MUSCLE Bronchial and Intestinal smooth muscles stimulated  Bronchospasm and Increased peristalsis
  • 12. III. Sensory neurons 5-HT receptors located on sensory neurons mediate a depolarizing response causing:pain, itching, respiratory stimulation, Bezold Jarisch reflex.
  • 13. CARCINOID TUMOURS Tumours of Enterochromaffin cells in G.I.T. produce large quantities of 5-HT  Diarrhaea; Bronchospasm; Edema; Vasodilatation & Flushing; Release of Substance P; Formation of Kinins. Excessive utilization of Tryptophan  Tryptophan Deficiency PELLAGRA
  • 14. I. 5-HT AGONISTS 1. BUSPIRONE Anxiolytic 2. TRIPTANS i) Sumatriptan ii) Naratriptan iii) Rizatriptan iv) Zolmitriptan Treatment of Acute Migraine Headache 3. CISAPRIDE Gastro Esophageal Reflux
  • 15. Sumatriptan is a selective agonist of 5-HT1 receptors, highly effective in treating acute attacks of migraine. It relieves the nausea and vomiting, but the headache may recur, necessitating repeated administrations. • Adverse effects include flushing and heat at the injection site, neck pain, dizziness, and tingling of the hands. • The drug is contraindicated with symptomatic ischemic heart diseases, angina, and hypertension as it may cause coronary vasoconstriction.
  • 16. II. 5-HT ANTAGONISTS 1. Ketanserin Hypertension (α 1 blockade) Vasospastic conditions 2. Methysergide (Sansert) Prophylaxis of Migraine
  • 17. 3. CYPROHEPTADINE (Periactin); also blocks H1 Stimulation of appetite; Smooth muscle manifestations of carcinoid tumours. Post-gastrectomy dumping syndrome; Cold induced urticaria. 4. CLOZAPINE Antipsychotic (Schizophrenia)
  • 18. 5. Risperidone (Blocks D2 also) Schizophrenia 6. Ritanserin Reduction of thromboxane formation 7. Ondansetron Nausea and Vomiting associated with cancer chemotherapy.
  • 19. 8. Granisetron As above 9. Alosetron Irritable bowel syndrome.
  • 20. SELECTIVE SEROTONIN REUPTAKE INHIBITORS CITALOPRAM FLUOXETINE FLUVOXAMINE PAROXETINE SERTRALINE
  • 21. Very commonly used class of Antianxiety and Antidepressant agents. Like Tricyclic antidepressants, which block NE uptake, the SSRIs block neuronal transport of Serotonin.
  • 22. Increased synaptic availability of Serotonin stimulates a large number of Post-synaptic 5-HT receptor subtypes. ____________________________________ SIDE EFFECTS •Nausea and Vomiting •Risk of Agitation and Restlessness
  • 23. RELEASE REUPTAKE
  • 24. Lysergic Acid Diethylamide (LSD) TRYPTAMINERGI C NEURON Psychedelic Sumatripta Hallucinati on 5- Fluoxetine 5- HT 2A HT 1D Antimigrain e Ondansetro 5-HT-retuptake Inhibitor Antidepressant n n 5-HT 3
  • 25. QUESTIONS
  • 26. 1. A patient has been diagnosed with a rare metastatic carcinoid tumor. The neoplasm is releasing serotonin, bradykinin and several unknown peptides. The effects of serotonin in this patient are most likely to include which one of the following: a) b) c) d) e) Constipation Episodes of bronchospasm Hypotension Hypersecretion of gastric acid Urinary retention
  • 27. 2. In recommending treatment for a patient suffering from metastatic carcinoid tumors the one least likely to be helpful is : a) b) c) d) e) Cyproheptadine Ketanserin Phenoxybenzamine Sumatriptan Ondansetron
  • 28. 3. A patient undergoing cancer chemotherapy is vomiting frequently. A drug that might help in this situation is : a) b) c) d) e) Bromocriptine Cimetidine Ketanserin Loratidine Ondansetron
  • 29. 4. Which of the following is a serotonin agonist useful for aborting an acute migraine headache and is not derived from a fungus : a) b) c) d) e) Bromocriptine Cimetidine Ergotamine Ketanserin Sumatriptan

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