Thermo-coagulation in Destruction of Tissue in Cerebral Cortex of Small Animals

In order to overcome certain mechanical difficulties inherent in the trephining method when applied particularly to the removal of tissue in the none too accessible auditory areas of the rat's cerebral hemispheres, the technic about to be described was devised.

Although Dennis and Bolton 1 suggested certain advantages of the thermo-coagulation method for the induction of lesions in the rat's brain, they made no attempt to describe in detail the procedures used to induce circumscribed lesions of varying magnitudes and depths in the brains of small animals frequently used in laboratories. The present technic, in brief, has involved the application of a heated platinum wire to a selected area of the exposed skull bone. This wire is left upon the skull for an interval, the magnitude of which depends upon the nature and purpose of the experiment. Microscopic study of the cerebral tissue, following sectioning and staining, indicates clearly that differential destruction of specific cortical layers may be effected by varying the duration of the application of the heated cautery wire to the external surface of the skull. Careful observation of other layers of the cerebrum indicates that the lesions so induced are clearcut and that adjacent cells are normal in appearance.

The data available have been accumulated from the study of the cerebral areas of 35 rats. These animals, all male albinos, were 3 months of age at the time that the cortical operations were performed. The results indicate that the application of the heated cautery tip to the skull for a period of 10 seconds effects the destruction of the outer or first cellular layer of the cortex within the auditory area. 2 If the wire is applied for 20 seconds all cortical layers within this region underlying the tip are destroyed.