BEHAVIOR/CHRACTERISTICS

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
* This investigation was supported by P.H.S. Grant CA 06010-04, N.I.H.; Grant No. MH 0819841, the
Committee on Faculty Research, Dartmouth College; and (in part) by P.H.S. Research Career Program
Award I-K6-CA 22,652-Ol from the National Cancer Institute. We thank D. C. Downie for assistance.
t The authors, in the order listed, are now at Stanford University, Dartmouth Medical College, and
McGill University.
$ We wish to emphasize that we do not claim that the pathological state studied here is the same as
Down’s syndrome. While the term ‘mongolism’ seems to us to be a good descriptive title for the hamster
disease, by analogy with the human syndrome of the same name, the question of whether the hamster
disease resembles this, or any other human disease, in any aspect of its etiology, is completely open at this time.
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