Histamine and Antihistamines, Pharmacology, Animation

00:03:40
https://www.youtube.com/watch?v=N9pr28Ht_EQ

Zusammenfassung

TLDRAntihistamines are drugs that inhibit the action of histamine, a compound involved in allergic reactions and various bodily functions like immune response and gastric acid secretion. Histamine, synthesized from histidine, is stored in mast cells and acts on four histamine receptors (H1-H4). H1-antihistamines are primarily used for allergy treatment, combating symptoms like itching and swelling, while H2-antihistamines target gastric acid disorders. First-generation antihistamines can cause sedation as they cross the blood-brain barrier, whereas second-generation ones are more selective for H1 receptors and less sedating. The release of histamine leads to blood vessel dilation and increased permeability, which can result in severe reactions like anaphylaxis.

Mitbringsel

  • 💊 Antihistamines counteract the action of histamine.
  • 🌐 Histamine mediates allergic responses and various bodily functions.
  • 📦 Most histamine is stored in mast cells found in tissues.
  • 📊 H1 and H4 receptors are involved in allergic inflammation.
  • 🩺 H2-antihistamines treat gastric acid disorders.
  • ⚠️ Allergic reactions can lead to symptoms like hives and difficulty breathing.
  • 🧠 First-generation antihistamines can cause drowsiness and cognitive impairment.
  • 🔍 Second-generation antihistamines are less sedating and more selective for H1 receptors.

Zeitleiste

  • 00:00:00 - 00:03:40

    The video explains antihistamines, which are drugs that counteract histamine—a compound involved in allergic reactions and other physiological processes like immune response, gastric acid secretion, and cognitive abilities. Histamine is synthesized from histidine and found in various tissues, predominantly in the skin, lungs, and gastrointestinal tract, stored in mast cells, and serves as a neurotransmitter in the brain. The video elaborates on histamine's binding to four types of G-protein-coupled receptors (H1-H4) that have distinct functions. H1 and H4 receptors are primarily involved in allergic reactions, whereas H2 receptors help regulate gastric acid secretion. H1-antihistamines are primarily used to treat allergies, causing symptoms like sneezing and swelling during allergic responses when mast cells release histamine. The video also discusses how first-generation H1-antihistamines can cause sedation by crossing the blood-brain barrier, whereas the second-generation antihistamines are less sedating due to their inability to cross this barrier and their selective action on H1 receptors.

Mind Map

Video-Fragen und Antworten

  • What are antihistamines?

    Antihistamines are medications that counteract the action of histamine.

  • What does histamine do in the body?

    Histamine mediates allergic reactions and is involved in immune response, gastric acid secretion, sleep-wake cycles, cognitive ability, and food intake.

  • What are the types of histamine receptors?

    There are four histamine receptors: H1, H2, H3, and H4, each with different functions and tissue expression.

  • What symptoms do antihistamines treat?

    Antihistamines are primarily used to treat allergic symptoms such as watery eyes, runny nose, and bronchospasm.

  • How do first-generation antihistamines affect the body?

    They can cross the blood-brain barrier causing drowsiness and cognitive impairment.

  • What are second-generation antihistamines?

    Second-generation antihistamines are less sedating and do not cross the blood-brain barrier as much as first-generation ones.

  • What is anaphylaxis?

    Anaphylaxis is a severe allergic reaction that can cause extensive vasodilation and bronchoconstriction.

  • What role do mast cells play in allergies?

    Mast cells release histamine and other chemicals upon re-exposure to allergens, triggering allergic responses.

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Untertitel
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Automatisches Blättern:
  • 00:00:03
    Antihistamines are medications that counteract the action of histamine.
  • 00:00:08
    Histamine is most notoriously known as a mediator of allergic reactions, but it’s also involved
  • 00:00:13
    in important physiological processes such as immune response, gastric acid secretion,
  • 00:00:19
    sleep and wake cycle, cognitive ability and food intake.
  • 00:00:25
    Histamine is synthesized from the amino acid histidine.
  • 00:00:28
    It is present in all tissues but most abundant in the skin, lungs and gastrointestinal tract.
  • 00:00:36
    Most of histamine in tissues is stored as granules inside mast cells.
  • 00:00:41
    In the brain, histamine also functions as a neurotransmitter.
  • 00:00:44
    It is found in histaminergic neurons of the hypothalamus, whose axons project throughout
  • 00:00:50
    the brain.
  • 00:00:52
    Histamine exerts its action by binding to histamine receptors, H-receptors, all of which
  • 00:00:58
    are G-protein- coupled.
  • 00:01:01
    There are four H-receptors, with different tissue expression patterns and functions.
  • 00:01:06
    Both H1 and H4 are involved in allergic inflammation, but only H1-antihistamines are currently available
  • 00:01:14
    for allergy treatment.
  • 00:01:16
    The major function of H2-receptor is to stimulate gastric acid secretion, so H2-antihistamines
  • 00:01:24
    are used to treat gastric acid disorders such as gastric reflux and peptic ulcers.
  • 00:01:30
    The term “antihistamine” generally refers to allergy-treating H1-antihistamines.
  • 00:01:37
    Most allergies occur upon a repeated exposure to an allergen.
  • 00:01:43
    Mast cells that were previously sensitized to the allergen are activated, releasing histamine
  • 00:01:48
    and other inflammatory chemicals.
  • 00:01:51
    Histamine causes dilation and increased permeability of blood vessels, stimulation of sensory nerves,
  • 00:01:58
    contraction of smooth muscle; and is responsible for most allergic symptoms, ranging from watery
  • 00:02:05
    eyes, runny nose, sneezing, itching; to swelling, hives, and difficulty breathing due to bronchospasm.
  • 00:02:14
    When released systemically, histamine can cause extensive vasodilation and bronchoconstriction
  • 00:02:21
    which may lead to life-threatening anaphylaxis.
  • 00:02:25
    Most H1-antihistamines are not similar to histamine in structure and do not compete
  • 00:02:31
    with it for binding to H1-receptor.
  • 00:02:33
    Instead, they bind to a different site on the receptor and stabilize it in its inactive
  • 00:02:39
    state.
  • 00:02:40
    The first-generation H1-antihistamines derive from the same chemical class as muscarinic,
  • 00:02:47
    adrenergic and serotonin antagonists, so they also have anti-cholinergic, anti-adrenergic,
  • 00:02:54
    and anti-serotonin effects.
  • 00:02:57
    More importantly, they can cross the blood-brain barrier and interfere with histamine functions
  • 00:03:02
    in the brain, causing drowsiness, cognitive impairment and increased appetite.
  • 00:03:07
    Some of these drugs are actually used for their sedative side effect, as sleeping aid
  • 00:03:13
    medications.
  • 00:03:15
    Second-generation antihistamines are less able to cross the blood-brain barrier, and
  • 00:03:19
    are therefore minimally or non-sedating.
  • 00:03:23
    They are also highly selective for H1-receptor and have no anti-cholinergic effects.
Tags
  • Antihistamines
  • Histamine
  • Allergic Reactions
  • Mast Cells
  • H1 Receptor
  • H2 Receptor
  • First-Generation
  • Second-Generation
  • Anaphylaxis
  • Gastric Acid