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Ca2+ channels
Low voltage-activated, voltagedependent transient current; channels deactivate slower than L or N channels. Moderately high-voltage non-inactivating,
Octanol, flunarizine
TOXINS: Funnel
- 10-12 ps
P
activated;
/ FUNCTIO:G
Identified in some CNS neurones (prominent in Purkinje cells).
Influence on SA pacemaker activity in heart, and repetitive spike activity in neurones and endocrine cells.
Identified only in neurones; participate in neurotransmit~er release.
Excitation-contraction coupling; critical to cardiac muscle contraction, and involved in most forms of smooth muscle contraction. Excitation-secretion coupling in endocrine ceils and some neurones.
LOCATION
‘nomenclature as agreed by the IUPHAR Committee on Calcium Channels [5pedding, M. and Pitoletti, I? (1992) 1. Plmrvmcc~l.Rw 44,363-3761 ‘Iwith -100 mM Baz+as charge carrier %ate of inactivation may be greatly accelerated by [C~I*+]~; N-type channels show slow transitions between inactivating and non-inactivating states
Structural information: The L channel from skeletal muscle is heterooligomeric and composed of oil, ~2, fl, yand 6 subunits. The oil subunit provides the binding site for L channel blockers. Different types of al subunit, present in skeletal and cardiac muscle and brain, are encoded by distinct genes; alternative splicing may also occur. Each ul subunit includes four homologous repeats containing six membrane-spanning regions, and shares significant homology with other voltage-gated ion channels, particularly the Na+ channel.
web spider toxin (FTX), wagatoxin IVA (but not sensitive to o-conotoxin, except MVIIc dihydropyridines or Wagatoxin IIIA)
(nonselective)
High-voltage activated, voltagedependent; moderate rate of inactivation6.
-8yS
(GIVA)
T
oconotoxins
TOXINS:
High-voltage activated, voltagedependent long-lasting current responsive to dihydropyridines (agonists and antagonists) and modulated by protein I-inase Adependent phosphorylntion. Slow inactivation%
PROPERTIES
- 12-20 ps
Dihydropy~dine antagonists, phenylalkylamines, benzothiazepines TOXINS: calciseptine
BLOCKERS
N
CONDUCTANCE+
-25~s
TYPE*
L
CHANNEL
1
Octanol, flunarizine
TOXINS: Funnel
- 10-12 ps
P
activated;
/ FUNCTIO:G
Identified in some CNS neurones (prominent in Purkinje cells).
Influence on SA pacemaker activity in heart, and repetitive spike activity in neurones and endocrine cells.
Identified only in neurones; participate in neurotransmit~er release.
Excitation-contraction coupling; critical to cardiac muscle contraction, and involved in most forms of smooth muscle contraction. Excitation-secretion coupling in endocrine ceils and some neurones.
LOCATION
‘nomenclature as agreed by the IUPHAR Committee on Calcium Channels [5pedding, M. and Pitoletti, I? (1992) 1. Plmrvmcc~l.Rw 44,363-3761 ‘Iwith -100 mM Baz+as charge carrier %ate of inactivation may be greatly accelerated by [C~I*+]~; N-type channels show slow transitions between inactivating and non-inactivating states
Structural information: The L channel from skeletal muscle is heterooligomeric and composed of oil, ~2, fl, yand 6 subunits. The oil subunit provides the binding site for L channel blockers. Different types of al subunit, present in skeletal and cardiac muscle and brain, are encoded by distinct genes; alternative splicing may also occur. Each ul subunit includes four homologous repeats containing six membrane-spanning regions, and shares significant homology with other voltage-gated ion channels, particularly the Na+ channel.
web spider toxin (FTX), wagatoxin IVA (but not sensitive to o-conotoxin, except MVIIc dihydropyridines or Wagatoxin IIIA)
(nonselective)
High-voltage activated, voltagedependent; moderate rate of inactivation6.
-8yS
(GIVA)
T
oconotoxins
TOXINS:
High-voltage activated, voltagedependent long-lasting current responsive to dihydropyridines (agonists and antagonists) and modulated by protein I-inase Adependent phosphorylntion. Slow inactivation%
PROPERTIES
- 12-20 ps
Dihydropy~dine antagonists, phenylalkylamines, benzothiazepines TOXINS: calciseptine
BLOCKERS
N
CONDUCTANCE+
-25~s
TYPE*
L
CHANNEL
1