Behavioral characteristics associated with the rat-virus-induced 'hamster mongolism' syndrome.

KILHAM~ found that hamsters inoculated intracerebrally (i.c.) with sub-lethal doses of rat virus (RV) during the first few weeks of life developed a number of abnormalities. The symptoms produced by the virus, which was originally isolated from rats bearing spontaneous or transplantable tumors, included stunted growth, malformed teeth,2 broadened facial bones, and protrusions of the eyes and tongue. The affected hamsters are somewhat ‘mongoloid’ in appearance (see Fig. 1). TOOLAN~ had previously reported similar abnormalities resulting from inoculation of hamsters at birth with cell-free filtrates of human tumor cells as well as certain tissues derived from human beings and rats carrying spontaneous cancers. The syndrome has been described previously as ‘hamster mongolism’.297 This syndrome is to be distinguished from other abnormalities which are produced in hamsters by the same virus when inoculation occurs at developmentally different times. The use of the term ‘mongolism’ should not be interpreted to imply any relation other than a superficial resemblance to the human syndrome of the same name.$ We thought it of interest to investigate the behavioral characteristics of hamsters afflicted with this syndrome. We have carried out a series of experiments in which hamsters with virus-induced ‘mongolism’ have been compared with normal hamsters on several standard behavioral tests. In the first experiment, differences in learning curves for shuttle-box avoidance learning were found, suggesting that affected hamsters were slow learners as compared to normal controls. However, further avoidance conditioning experiments found that this difference, while replicable, is highly variable. In two experiments a similar rate difference was found, in a third no rate difference appeared, and the overall performance level of the affected