[In vitro analysis of temperature-sensitivity of neurons in the rat dorsal motor nucleus of the vagal nerve].

Extracellular and intracellular recordings were made from neurons in the rat dorsal motor nucleus of the vagal nerve (DMV) in vitro to investigate the thermosensitivity of their firing rates and membrane properties. Out of 69 neurons which were extracellularly recorded, sixteen (23%) were warm-sensitive neurons and three (4%) were cold-sensitive neurons. The thermosensitivity of all the neurons tested was preserved during the synaptic blockade in a low Ca2+ (0.2 mM)/high Mg2+ (12 mM) solution. Intracellular recordings demonstrated that warm-sensitive neurons depolarized with a decrease in the input resistance (Rinput) during warming of the brain tissue. The responses of warm-sensitive neurons were completely abolished in the low Ca2+/high Mg2+ solution which contained TTX (5 microM). Cold-sensitive neurons showed a hyperpolarization with a decreased Rinput during warming, whose reversal potential was about-83 mV. Both the hyperpolarization and the reduced Rinput of cold-sensitive neurons during warming were partially suppressed by perfusion with 10 mM of TEA. Therefore, it is concluded that the depolarization of warm-sensitive neurons during warming is seemed to be caused, at least in part, by opening of the TTX-sensitive Na2+ channels, while the depolarization of cold-sensitive neurons during cooling is largely determined by closure of the K+ channels.