Serial Frozen Section of Whole Brain

During the past decade, reconstructions of monkey brains lesioned or implanted for behavioral studies have been time consuming. The imbedding process especially has taken precious months that delay completion of an otherwise finished study. To overcome this difficulty the present method, developed for rapid location of electrode implant sites, was modified to allow serial analysis of whole monkey brains. At the time Ss are sacrificed their brains are perfused with 10% formalin. The brain is then fixed for a week in 10% formalin ( a rat brain requires only 48 hr.), neutralized with chalk or CaC1: after which a small unwanted portion, caudally or rostrally, is cu: away and a small metal pin is inserted to form a guide hole through the entire length of brain. The brain is then placed in 20% alcohol for 36 hr. If a Technicon is available or a Lipshaw Tissue Plunger and Rotator, the time can be shortened to 12 hr. When ready co section, the metal pin is removed and the brain is frozen, using a freezing block in which dry ice is evaporated in 70% alcohol. For most work, a modification of the type furnished by the American Optical Co. is advantageous. The well is enlarged to permit greater circulation of the alcohol and better temperature control. The mounting base for the brain in the well is made removable and interchangeable so that other mounting bases of varying diameters can be used for different size brains or tissue blocks. Sections are floated in 20% alcohol and mounted onto prepared glass slider with the aid of a sable brush. Sections adhere to the slides beccer if Mayer's fixative is applied the day before needed, and the slides incubated at 37OC overnight. The slides can be nutnbered at this time, using Labink, which after it has dried overnight does not come off during any staining process. An entire monkey brain can be sectioned, requiring 5 to 7 hr. of fairly constant temperame control. In this instance, a single, large, thick piece of dry ice is used. If it is of such diameter and height chat, as it melts, it fills the entire freezing well around the mounted brain and yet retains the same height as the brain, a more even temperature is obtained. Thus, as one sections, the ice melts just fast enough to clear the edge of the knife as it is drawn across. Intermittent cutting, as well as uneven freezing, resulcs in poor sections. This is especially true of larger mounts where not only the temperature but the sectioning should be fairly constant

Section (typography · Anesthesia and Neurotoxicity Research · Computer Science · Psychology