Canine Brain in Stereotaxic Coordinates

Despite the increasing uses of the dog as an experimental animal by biomedical investigators with interest in neurophysiology and experimental neurology, work with precise neuro-anatomical analysis has been limited. The inadequacy of available stereotaxic coordinates and the enormous variability of dogs' heads have contributed to this situation. Doctors Dua-Sharma, Sharma, and Jacobs have produced the first stereotaxic atlas of the entire canine brain, using full sections in frontal, sagittal, and horizontal planes from only one breed of dog to achieve uniformity of dimension.The work grew out of their own needs, encountered in collaborative study of the regulation of food and water intake at St. John's Medical College in Bangalore, India, the U.S. Army Laboratories in Natick, Massachusetts, the University of Illinois, and the University of Rochester School of Medicine.Forty-six beagle or beagle-type dogs were used. Because the greatest variations in skull shape appear facially, precise landmarks and definitions were noted to ensure accurate craniofacial measurements. For many tests, the authors used the stereotaxic assembly system developed at the Interscience Research Institute in Champaign, Illinois, in which preset alignment of x-ray tubes, electrode carriers, a ventriculographic needle, cassettes, and markers retain their relative positions in the 3-dimensional coordinate system defined by the stereotaxic instrument. Multiple marking electrodes were inserted in each dog's brain in order to determine the level of sections in the different planes as they related to the predetermined stereotaxic zero.Three series of plates present brain sections obtained from three dogs, one dog being used for each series. In addition to the standard millimetric grids, each plate is provided with four indicator lines aligned with the guide holes of the section. In this atlas, the horizontal zero plane is not raised 10 mm, but corresponds exactly to the instrument zero horizontal and passes through the axis of the ear bars used to position the animal's head in the apparatus.Part I is composed of seventy-two pairs of plates showing frontal sections with right-facing pages stained and labeled for fibers and left-facing pages stained and labeled for cells. Part II contains plates of thirty-one sections cut in the sagittal plane and stained for fibers only. Twenty-eight sections cut in the horizontal plane and stained for fibers only are included in part III.Each brain was perfused with balanced salt solution, the calvarium removed, and further measurements taken both at that time and again after several days of preservation in 10% formalin. To relate anatomical brain sites to craniofacial and internal brain landmarks, variability estimates were performed and the alignment and shrinkage validated.