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Related Concept Videos

Adrenergic Receptors (Adrenoceptors): Classification01:27

Adrenergic Receptors (Adrenoceptors): Classification

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Adrenergic receptors, or adrenoceptors, respond to the autonomic neurotransmitter noradrenaline and other endogenous catecholamine agonists. They are classified into two main families, α and β, based on their pharmacological response and are further subdivided depending on their location, elicited response, and affinity to specific agonists or antagonists.
α-Adrenoceptors
α-Adrenoceptors are classified into two main subtypes: α1 and α2. The α1 adrenoceptors,...
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Adrenergic Receptors: ɑ Subtype01:31

Adrenergic Receptors: ɑ Subtype

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Adrenoceptors are classified into α and ꞵ classes based on their potencies to catecholamine agonists. α-adrenoceptors show the following order of catecholamine potency:
Adrenaline ≥ Noradrenaline >> Isoprenaline
α-adrenoceptors are further divided into α1 and α2-adrenoceptors.
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Adrenergic Receptors: β Subtype01:26

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β-adrenoceptors have varied sensitivities towards adrenaline, noradrenaline, and isoprenaline. The order of agonist potency is as follows:
Isoprenaline > Adrenaline > Noradrenaline
Neurotransmitter binding to these receptors causes activation of adenylyl cyclase resulting in increased concentrations of cAMP and modulation of calcium ion channels within the cell. They are further classified into β1, β2, and β3 subtypes.
β1-adrenoceptors: β1-adrenoceptors...
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Adrenergic Neurons: Neurotransmission01:27

Adrenergic Neurons: Neurotransmission

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Postganglionic sympathetic fibers (except those supplying the sweat glands) releasing noradrenaline or norepinephrine are called noradrenergic or adrenergic neurons. Noradrenaline, dopamine, adrenaline, or epinephrine are collectively called "catecholamines" as they contain a catechol moiety and an amine side chain. The five stages of neurotransmitter release involve their synthesis, storage, release, reuptake and metabolism.
Synthesis: Catecholamine synthesis requires tyrosine, which...
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Sympathetic Signaling01:32

Sympathetic Signaling

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Sympathetic signaling, a vital part of the autonomic nervous system, plays a crucial role in mobilizing the body's resources in response to stress or emergencies. It involves the transmission of nerve impulses from sympathetic preganglionic fibers to postganglionic fibers. This results in the release of specific neurotransmitters and activation of adrenergic receptors.
Sympathetic preganglionic fibers release the neurotransmitter acetylcholine (ACh) onto the ganglionic neurons in the...
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Drugs Affecting Neurotransmitter Release or Uptake01:21

Drugs Affecting Neurotransmitter Release or Uptake

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Certain drugs can affect how neurotransmitters called catecholamines, are released or taken back up in the adrenergic neuron. They can have different effects on the body's sympathetic transmission. Reserpine, a natural compound found in the Rauwolfia shrub, blocks a transporter called vesicular monoamine transporter (VMAT), which leads to a buildup of catecholamines in the cell and reduces sympathetic transmission. Another drug called guanethidine works in multiple ways, including blocking...
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Measuring the Rate of Lipolysis in Ex Vivo Murine Adipose Tissue and Primary Preadipocytes Differentiated In Vitro
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Presynaptic Adrenoceptors.

Bela Szabo1

  • 1Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany. szabo@pharmakol.uni-freiburg.de.

Handbook of Experimental Pharmacology
|May 16, 2024
PubMed
Summary
This summary is machine-generated.

Presynaptic alpha2-adrenoceptors on neurons regulate neurotransmitter release. Their activation inhibits noradrenaline release, impacting conditions like hypertension and depression.

Keywords:
AdrenoceptorAlpha-adrenoceptorAxon terminalBeta-adrenoceptorClonidineDexmedetomidineExocytosisMirtazapineNoradrenalinePresynaptic receptorSynaptic transmissionTransmitter releaseVoltage-gated calcium channel

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Area of Science:

  • Neuroscience
  • Pharmacology

Background:

  • Presynaptic alpha2-adrenoceptors (α2-ARs) are found on peripheral and central nervous system neurons.
  • Activation of α2-ARs inhibits the release of neurotransmitters like noradrenaline.
  • The α2A-receptor subtype is primarily involved in this inhibitory mechanism.

Purpose of the Study:

  • To elucidate the molecular mechanisms linking α2-AR activation to inhibited neurotransmitter release.
  • To explore the physiological role of endogenous noradrenaline in autoinhibition.
  • To review the therapeutic applications of α2-AR modulators.

Main Methods:

  • The abstract does not detail specific experimental methods but discusses established knowledge on receptor function and molecular pathways.
  • Review of literature on α2-adrenoceptor pharmacology and physiology.
  • Analysis of the molecular cascade from receptor binding to transmitter release inhibition.

Main Results:

  • Activation of presynaptic α2-ARs, particularly α2A, inhibits exocytotic release of noradrenaline and other transmitters.
  • Endogenous noradrenaline triggers retrograde autoinhibition of its own release via α2-ARs.
  • β2-adrenoceptors enhance transmitter release but are not activated by endogenous adrenaline.

Conclusions:

  • Presynaptic α2-ARs are key regulators of noradrenergic and non-noradrenergic neurotransmission.
  • Modulation of α2-ARs has significant therapeutic potential, as seen with antihypertensive, sedative, analgesic, and antidepressant drugs.
  • Understanding these mechanisms is crucial for developing targeted pharmacological interventions.