The cryoloop: an adaptable reversible cooling deactivation method for behavioral or electrophysiological assessment of neural function

We describe a very adaptable reversible inactivation technique for the beha vioral or electrophysiological analysis of neural circuits. The cryoloop de vice can be permanently implanted or topically applied in an acute preparat ion to apply cold to discrete surface regions of the central nervous system (e.g. cerebral cortex or midbrain). The cryoloop consists of a custom shap ed, stainless steel, hypodermic tubing and cooling is effected by passing c hilled methanol through the lumen of the tubing. Cryoloop temperature is mo nitored by a microthermocouple attached to the union of the loop, and can b e maintained within +/- 1 degrees C of a desired temperature. In chronic pr eparations, implanted cryoloops have been maintained in cats and monkeys fo r periods in excess of 2 years. After this period there are no structural, metabolic of functional changes in the deactivated tissue, and full reversi bility of cooling-induced effects is maintained. Operation of multiple cryo probes provides great flexibility of experimental protocols, permits double and triple functional dissociations to be made, and strengthens experiment al design considerably. (C) 1999 Elsevier Science B.V. All rights reserved.