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SEROTONIN OR 5-HT (+ antagonists) (ANTAGONISTS OF 5-HT (Ketanserin …

- - - - 90% ECs/ 10% neurons
- - - - Depolarization of nerve endings & opening of channels (M type)
        indirect & reflex effects
        
        Somatic & ANS: pain/itch/ :crown: chemoreflex - :arrow_heading_down: BP/bradycardia
        Myenteric plexus nerve endings: augmentation of peristalsis & emetic reflex
        Brain: Area postrema and NTS; :nauseated_face:
        :black_flag: :pill: Ondansetron
    - - Gq - IP3/DAG
        
        2A: postjunctional (D type) - direct actions
        smooth mm, platelets & cerebral neurons
        vasoconstriction,
        intestinal/uterine/bronchial constriction
        platelet aggregation
        :check: cerebral neurons
        :black_flag: :pill: ketanserin
        
        2C: vasodilation through EDRF
        choroid plexus
    - - Gs type of receptor
        
        Brain: hippocampus area, slow K+ channel
        :red_flag: :pill: Cizapride
        :black_flag: :pill: Renzapride, Metoclopramide
    - - autoreceptors that :red_cross: firing of neurons or release of 5-HT
        :check: K+ channel
        :check: Ca2+ channel
        Gi/ Go
        
        1D: Basal ganglia & substantia nigra - dopeminergic
        
        1B/D: Cranial blood vessels; causes vasoconstriction
        :red_flag: :pill: sumatriptan; selective agonist
        
        1A: Brainstem (raphe nuclei) + hippocampus
        :white_flag: :pill: Buspirone; partial agonist
- - - - :no_entry: H1
        anti-histamine/cholinergic, sedative
        :star: increase appetite
      - Allergic reactions; hay fever
        Serotonin syndrome
        Carcinoid syndrome
        Priapism (FLUOXETINE)
        :ballot_box_with_check: appetite in children
      - :no_entry: 5-HT2A
      - ADRs
        
        weight gain
        
        drowsiness
        
        dry mouth
  - - - Diverse pharmacological effects
        
        Dihydroergotamine (DHE)
        
        Better a-blocking action
        lesser everything else
        
        Pharmacokinetics
        
        poor bioavailiabilty
        slow/incomplete absorption
        first-pass metabolism
        
        Sublingual/rectal administration
        metabolised in liver & excreted in bile
        
        Cross BBB
        
        t1/2 = 2hrs
        
        Ergotamine
        
        :white_flag: and :black_flag: 5-HT1/2
        
        Sustained vasoconstiction, visceral smooth muscke contraction and vasomotor centre depression
        
        Potent emetic via CTZ & oxytotic
        
        Prolong use
        
        vasoconstriction
        
        damaged endothelium
        
        ADRs
        :nauseated_face:, muscle cramps, weakness, :pushpin:, coronary/other vasospasm, chest pain
        
        Ergometrine
        
        :white_flag: 5-HT in uterus
        placenta
        umbilical blood vessels
        brain
        
        Weak agnoist/ :forbidden:antagonists on a-receptors
        
        :black_flag:5-HT1 in intestines
        
        C/I :eight_pointed_black_star:
        Sepsis
        IHD
        peripheral vascular dz
        HTN
        Liver disease
        :pregnant_woman::skin-tone-3: