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

Area of Science:

• Biomedical Engineering
• Physiology
• Neuroscience

Background:

• Accurate measurement of deep body core temperature is crucial for physiological research.
• Silicon diodes offer a potential method for precise, long-term temperature monitoring.
• Understanding brain temperature regulation is key to comprehending thermoregulation.

Purpose of the Study:

• To describe an electronic circuit for temperature measurement using silicon diodes.
• To assess the long-term stability and accuracy of silicon diode temperature sensors implanted in rabbits.
• To investigate the relationship between brain temperature and rectal temperature under various physiological conditions.

Main Methods:

• Development of an electronic circuit utilizing the linear relationship between diode reverse current and temperature.
• Calibration and implantation of silicon diode sensors into various body core sites in rabbits.
• Simultaneous measurement of temperatures at the atlanto-occipital membrane, intracisternally, and rectally.
• Observation of temperature dynamics during fever and defervescence, including cutaneous vasoconstriction and thermal panting.

Main Results:

• Silicon diode sensors maintained accurate temperature sensing capabilities for over a year post-implantation.
• Atlanto-occipital membrane and intracisternal temperatures were consistently higher (approx. 0.3°C) than rectal temperature.
• This temperature gradient remained consistent across different states of cutaneous vasoconstriction and thermal panting.

Conclusions:

• Implanted silicon diodes provide a stable and accurate method for long-term deep body temperature monitoring.
• Brain temperatures in regions like the cerebellum and medulla oblongata do not appear to be actively cooled during heat dissipation responses.
• The findings challenge the proposed protective role of brain cooling in regulating thermoregulatory effector mechanisms.