Figure 1.

Activation of an inward current by heat in primary sensory neurons. (A) Membrane current activated in a heat-sensitive and a heat-insensitive neuron in response to a temperature change from 25°C to 49°C (timing of solution change given by top trace, obtained by measuring time course of change in solution conductance at pipette tip after detaching from the cell at the end of the experiment). In 56% (n = 155) of small neurons (<25 μm in diameter), a delayed increase in membrane current exceeding 50 pA was observed in response to a 49°C pulse; such neurons were classified as heat-sensitive. (B) Same traces as in A expanded to show delayed onset of current increase in heat-sensitive neurons.