Temperature-dependent subconducting states and kinetics of deltamethrin-modified sodium channels of neuroblastoma cells.

The effects of temperature on the properties of sodium channels from mouse neuroblastoma cells modified by the pyrethroid insecticide deltamethrin were investigated using the patch-clamp technique. The study was aimed at determining various states of modified channels which were expected to be revealed by raising the temperature as a result of an increase in channel activity. After exposure to 10 microM deltamethrin, the decay of whole cell sodium current at -30 mV was drastically slowed. It is expressed by two exponential functions at 11 degrees C and by three exponential functions at room temperature (22 +/- 1 degree C). Thus, raising the temperature reveals a new process. Whole cell sodium tail currents associated with step repolarization from -30 mV to -100 mV were best fit by the sum of two exponential functions both at 11 degrees C and at room temperature. The decay of the summed modified single sodium channel currents at -30 mV was expressed by a single exponential function at 11 degrees C, and by two exponential functions at room temperature. In keeping with these results, the open time histograms show the single (11 degrees C) and double (room temperature) exponential distributions. Thus, raising the temperature allows a new single channel process to be revealed. Other modified open states observed previously at 11 degrees C were also found at room temperature including a flickering state and a subconducting state. In addition, several new subconducting states were found at room temperature.(ABSTRACT TRUNCATED AT 250 WORDS)