Calcium channel
As calcium channels, outdated calcium channels, ion channels are referred to in the physiology and cell biology, which are more or less selectively permeable ( permeable ) for calcium ions (Ca2 ). A distinction is made between voltage-gated and ligand -regulated calcium channels. Therapeutically, of particular interest are the voltage-dependent L-type channels and T-type.
Physiological function
Changes in intracellular calcium concentrations is crucial for many physiological processes. They cause the electromechanical coupling in muscle contraction, leading to synthesis and secretion of neurotransmitters and hormones that regulate the expression of genes and control enzyme activities. The major part of the calcium influx into the cell via voltage-dependent calcium channels, whose opening stimulus represents the depolarization of the cell membrane. Modulating here engage hormones, protein kinases, protein phosphatases, toxins and drugs.
Voltage-gated calcium channels ( VGCCs abbreviated, voltage - gated Ca2 channels) have an important meaning in the context about with the pain. As voltage-controlled Ca2 - channels are provided on the cell surfaces of excitable cells such as neurons, muscle, endocrine cells also expressed or available and transfer an action potential in a Ca2 - pulse. These calcium channels can be due to their voltage sensitivity ( see ion channel ), divided their activation kinetics and their pharmacological profile in different categories:
- L- type (" l" onglasting, long-lasting power ),
- T-type ( "t" ransient, low power )
- N- type (" n " either L or T in "N" Euronen )
- P / Q-type (in " P" urkinje cells of the cerebellum ( cerebellum) ) and the
- R- Type ("r" emaining ) VGCCs (voltage - gated Ca2 channels).
The activation of L -, P-, Q - and N -type calcium channels by different stimuli in Spinalneuronen is involved in the perception of acute pain, hyperalgesia and allodynia. So far, the N -type calcium channels are the most studied scientifically, they are localized at the presynaptic nociceptive nerve endings and trigger the release of the neurotransmitter substance P and glutamate. They can be specifically blocked by ω - conotoxins, among others.
Medical importance
In the treatment of heart disease and high blood pressure known as calcium channel blockers are used. They regulate the force of contraction of cardiac muscle and smooth muscle of blood vessels. The calcium channel blockers inhibit the flow of calcium ions into the muscle cells; Calciumioneneinstrom this is the cause of the muscle contraction, as it initiates the actin -myosin cross- bonding. A more calcium channel antagonist is nimodipine, which is used as the anti-dementia drug, ie for the treatment of dementia. Flunarizine, a drug which also antagonized the calcium channel is used in migraine prophylaxis.
A number of agents that inhibit calcium channels, are used as anticonvulsants.