Long-term recording of core temperatures with chronically implanted silicon diodes.

An electronic circuit for measurement of temperatures is described utilizing silicon diodes as temperature sensors and the feature that the reverse current flow of a diode is linearly related to temperature. Once calibrated and implanted into various sites of the body core of rabbits, the diodes preserved their precise temperature sensing qualities for periods longer than a year. Temperature changes of the atlanto-occipital membrane were found to be close to simultaneously measured intracisternal temperature, both temperatures being some 0.3 degree C higher than rectal temperature. This temperature-relationship persisted under conditions with different states of cutaneous vasoconstriction and thermal panting as observed in fever and during defervescence. These results indicate that extrahypothalamic brain regions as the cerebellum and the medulla oblongata do not benefit from the proposed protective function of brain cooling during stimulation of heat dissipating effector mechanisms.