Low threshold calcium T-current IV curve geometry is alterable through the distribution of T-channels in thalamic relay neurons

Mike Neubig and Alain Destexhe

Neurocomputing 26-27: 215-221, 1999.

Abstract

Low-voltage-activated calcium T-channels enable low-threshold calcium spiking and associated bursting in thalamocortical relay neurons. One measure of this firing pattern is the geometry of the T-current's IV curve, of which the current/voltage (IV) peak is a fundamental index. Using reconstructed neurons, we show that: (1) in cells with equivalent IV peak currents, physiologically constrained distributions can shift the peak's voltage by 4.8 mV-which is just below the resolution at which IV data is usually gathered and corresponds to a change in the single-spike threshold from 5.4 to 29.3 pA; (2) in neurons with equivalent IV peak voltages, distribution can shift the peak current by 1.4 nA-which is on the order of 30% of maximal T-current in relay cells. Further, we show that these shifts are qualitatively different than those induced by eight other factors. We conclude that channel distribution is a primary factor shaping IV curve geometry.
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