Stereotaxic Coordinates of the Brain of the Golden Hamster (Mesocricetus Auratus)

During the course of investigating another problem, the writer placed lesions in neocortex and limbic system structures in 123 female Golden Hamsters weighing 90 to 110 gm. The stereotaxic coordinates for the hamster brain developed by Smith and Bodemer (1963) were used previously on 20 Ss both male and female and adjusted where necessary for these animals. The anterior-posterior coordinates of their atlas were not completely applicable to these Ss for accurately locating the septa1 area, cingulate gyrus, and the amygdala. However, once a structure or area was located, there was only a very small variation in the A-P dimension in animals of the same weight category (90, 100 or 110 gm.) and the intra-brain spatial relations which they report were very accurate. The work of the writer and of Smith and Bodemer was done on two different Stellartype stereotaxic instruments which were constructed at the same time in the University of Washington School of Medicine machine shop according to the design of Stellar and Krause (1954). A few minor modifications were incorporated but there were no major differences between the instrument Stellar and Krause describe and these two (Smith, personal communication, 1968). In addition to using an almost identical instrument, Ss were aligned as described by Smith and Bodemer. Their perfusion and frozen section technique was followed. The same histologist who prepared their work also sectioned and mounted many of the author's animals. The writer concludes that the work of Smith and Bodemer is highly reliable because once a structure is located other areas can be found following their insuuctions; however, their initial anterior-posterior directions may not bring E directly to the desired position. Their A-P locations can be used but may result in an anterior error of 2 mm. or more, depending on S's weight. A second conclusion is that this A-P difference is probably a constant error introduced by minor variations in the construction of the two stereotaxic instruments. Confirmation of the true distances of areas from ear bat zero for animals of various weights will have to come from future studies using a number of different instru