The effects of excessive heat on heat-activated membrane currents in cultured dorsal root ganglia neurons from neonatal rat

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Abstract
Re between 43 and 50°C exhibited a fast slope (Q10>10) that was similar both during rising and falling temperature (n=85). Temperatures exceeding 52°C resulted in slowdown in the recovery of Iheat, and the threshold for inducing Iheat was shifted to lower temperatures in successive trials. These high temperatures (54–60°C) caused a linear and incomplete recovery of Iheat (Q10 decreased to <5; 4.5±0.4; n=17) and in successive trials the threshold of Iheat decreased to temperatures close to that in the bath. The neurons, however, remained sensitive to capsaicin and to decreased extracellular pH. It is suggested that exposure of nociceptive neurons to excessive noxious heat results in an irreversible decrease of the energy barrier between the resting and activated state of the protein structures responsible for generation of Iheat. This may explain the sensitization of nociceptors after heat injury....