Calcium channel

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As calcium channels , outdated calcium channels are in the physiology and cell biology ion channels refers to the more or less selectively permeable (permeable) for calcium - ion (Ca 2+ are). A distinction is made between voltage-dependent and ligand-regulated calcium channels. The voltage-dependent L-type and T-type channels are of particular therapeutic interest .

Physiological function

Changes in the intracellular calcium concentration are crucial for many physiological processes. They cause the electromechanical coupling during muscle contraction , lead to the synthesis and secretion of neurotransmitters and hormones, regulate the expression of genes and control enzyme activities . The essential part of the calcium influx into the cell occurs via voltage-dependent calcium channels, the opening stimulus of which represents the depolarization of the cell membrane . Modulating access this hormone , protein kinases , protein phosphatases , toxins and drugs one.

Voltage-controlled calcium channels (abbreviated vgCaCh or VGCC, English voltage-gated Ca 2+ channel ) have an important meaning in connection with pain . Voltage-controlled Ca 2+ channels are made available or expressed on the cell surfaces of excitable cells such as neurons , muscle but also endocrine cells and transmit an action potential in a Ca 2+ pulse. These calcium channels can be divided into different categories based on their voltage sensitivity (see ion channel ), their activation kinetics and their pharmacological profile:

  • L-type ( "l" onglasting , long-lasting current),
  • T-type ( "t" ransient , low current),
  • N-type ( "n" either L or T, in "N" euros),
  • P / Q type (in “P” urkinje cells of the cerebellum ) and the
  • R-type ( "r" emaining ) VGCCs (voltage-gated Ca 2+ channels)

The activation of L-, P-, Q- and N-type calcium channels by various stimuli in spinal neurons is involved in the perception of acute pain, hyperalgesia and allodynia . So far, the N-type calcium channels have been best researched scientifically, they are located on the presynaptic nociceptive nerve endings and cause the release of the neurotransmitter substance P and glutamate . They can be blocked specifically by ω- conotoxins , among other things .

Medical importance

So-called calcium channel blockers are used in the therapy of heart diseases and high blood pressure . They regulate the contraction force of the heart muscles and the smooth muscles of the blood vessels . The calcium channel blockers inhibit the flow of calcium ions into the muscle cells ; This influx of calcium ions triggers the muscle contraction, as it initiates the actin - myosin cross-bridge bond. Another calcium channel antagonist is nimodipine , which is used as an anti- dementia agent, i.e. for the treatment of dementia . Flunarizine , a drug which also antagonizes the calcium channel, is used in migraine prophylaxis.

A number of active ingredients that inhibit calcium channels are used as anti-epileptic drugs. For example ethosuximide (T-type calcium channel), pregabalin and gabapentin (both P / Q-type calcium channel).

Toxins that bind calcium channels are calcicludin , calciseptin , ω-conotoxin , ω-agatoxin, and taicatoxin .

See also


Individual evidence

  1. M. Freissmuth et al.: Pharmacology & Toxicology. Springer, 2012, ISBN 978-3-642-12353-5 , p. 308.