An isolation protocol for testing anti-depressants and anxiolytics in the marmoset monkey

M.J. Jongsma¹, S.A.M. van Vliet^1,2, R.A.P. Vanwersch¹, I.H.C.H.M. Philippens^1,2

¹TNO Defence, Security and Safety, Dept. Diagnosis and Therapy, Rijswijk, The Netherlands
²Utrecht University, Dept. of Psychopharmocology, Utrecht, The Netherlands

Testing of anti-depressants or anxiolytics remains dependent to a great extent on the use of proper animal models of anxiety and depression. An ideal model would be one reproducing all features of human anxiety or depression. Therefore, an isolation protocol in a nonhuman primate has been developed in which a 'natural' expression of fear and depressive behavior is present. Separation from the social group is very stressful for nonhuman primates, elevating anxiety- and depressive-like behaviors.

To test anxiety and depression, different readout-systems were used resembling depressive-like behavior in human: observational recordings of anxiety- and depressive-like behavior, human threat test (HTT), startle reflex, body weight and activity.
" With the observations the occurrence of symptoms correlated to central effects and the condition of the animal are scored in detail. The following symptoms are observed: appetite, grooming, apathy (responsiveness to its surrounding), mobility, stereotypy (repetitive, patterned and rhythmic movement), stypic behavior (idiosyncratic non-locomotive stereotyped actions), passive (maintenance of non-locomotive behavior), huddle (fetal-like self-enclosed position), location (back of cage).
" In the HTT, the response to a human is observed. The following parameters are recorded: 1) time spent forward on perch, 2) time spent in nest box, 3) number of forward jumps, 6) body postures: tail postures (i.e. genital presenting), scent making, arched pilo, 7) Fear postures: slit stares (flattening of ear tufts and staring through reduced eye lids), rearing, twisting.
" For the startle reflex and activity computerized test systems are used.

In the new protocol these tests are performed during normal housing, during two weeks of isolation, and after re-socialization. During isolation, all parameters were affected. There was a clear correlation between the observational and quantitative parameters confirming the anxiety related behavior. After replacing the animals in the colony, most parameters recovered to normal. Only the depressive-like behavior was still present.

Paper presented at Measuring Behavior 2005 , 5^th International Conference on Methods and Techniques in Behavioral Research, 30 August - 2 September 2005, Wageningen, The Netherlands.

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