SOMATOSTATIN-IMMUNOREACTIVITY IN THE HIPPOCAMPUS OF MOUSE, RAT, GUINEA-PIG, AND RABBIT

The hippocampi of species commonly used for in vitro physiologic studi es were examined to determine if there were species-specific and regio nal differences in somatostatin immunoreactivity. The distributions of somatostatin-immunoreactive somata and fiber plexuses were determined , and the concentration of somatostatin along the septotemporal axis o f the hippocampus was measured using a radioimmunoassay. There are man y similarities in the patterns of somatostatin immunoreactivity in the hippocampi of mice, rats, guinea pigs, and rabbits. All species had a relatively even distribution of somatostatin-positive perikarya acros s three fields of the hippocampus (dentate gyrus, CA3, and CA1-2), a s imilar distribution of somatostatin-immunoreactive perikarya across th e strata of the CA1-2 field and the dentate gyrus; and more somatostat in-positive cells in temporal than in septal hippocampus. However, the re are species-specific differences in the distribution of somatostati n-immunoreactive perikarya across the strata of CA3. In addition, unli ke the other species examined, mice appeared not to have a somatostati n-immunoreactive fiber plexus in the molecular layer of the dentate gy rus. The functional signifi cance of these differences remains to be d etermined. (C) 1994 Wiley-Liss, Inc.