Presynaptic calcium currents and their relation to synaptic transmission: voltage clamp study in squid giant synapse and theoretical model for the calcium gate.
A voltage clamp study of the presynaptic terminal in squid stellate ganglion has given quantitative results relating inward Ca2+ current to presynaptic membrane potential and postsynaptic response to inward Ca2+ current. The results indicate an S-shaped curve for the relationship between presynaptic potential and Ca2+ current and a linear relationship between Ca2+ current and postsynaptic potential. A similar S-shaped curve was found for the time-dependent properties of the Ca2+ conductance. Based on these results a mathematical model was developed which accounts for the experimental results in this and previously published papers by other authors. The model suggests that five subunits are involved in the Ca2+ gate and that the subunits change noncooperatively from an inactive to an active form upon membrane depolarization.
D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D003201:Computers; D049832:Decapodiformes; D005724:Ganglia; D008564:Membrane Potentials; D008959:Models, Neurological; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission; D013816:Thermodynamics
D002118:Calcium