A miniaturized cryoprobe for functional neuronal blockade in freely moving animals

We have developed a miniature cryoprobe for blockade of neuronal structures. The cryoprobe uses Freon as a cooling medium and consists of concentric double stainless steel cannulae, a shaft heater coil and a tip thermocouple. The cryoprobe tip temperature is controlled by adjusting Freon flow supplying the cryoprobe by an automobile fuel injector and electronic control circuit, and is displayed on a temperature monitor. Tissue temperatures, determined by thermocouples, ranged from 8.5 degrees C near the cryoprobe tip to 20 degrees C 2.5 mm distal to the tip. The cryoprobe shaft is maintained at body temperature by means of a shaft heater coil and a heater control circuit. The cryoprobe offers advantages of ease of construction, and allows cooling of neuronal structures in freely moving animal preparations.