Human threat test: a method
to test anxiety-related behavior in a marmoset monkey
S.A.M. van Vliet1,2, M.J.
Jongsma1, R.A.P. Vanwersch1 and I.H.C.H.M. Philippens1,2
1TNO Defense, security and
safety, RG Toxicology and MedicalCounterMeasures, Rijswijk, The Netherlands
2Utrecht University, Dept. of psychopharmacology, Utrecht University,
Utrecht, The Netherlands
Defensive responses are components of the daily life of primates. These
responses are still present in captivity born animals. Based on this behavior,
the human threat test (HTT) is a widely used method in the assessment
of anxiety/fear related behavior in a non-human primate. The test is based
on findings that non-human primates will exhibit anxiety-related behavior
in the presence of a human observer. Retreating to the back of the cage
and display of aggressive and anxiety-related postures are the main pronounced
reactions.
This study focused on the effects of three psychoactive compounds on
the anxiety-related behavior of the marmoset monkey (Callithrix jacchus)
measured with the human threat test. First, the sedative compound diazepam,
known to decrease anxiety, was applied to validate the HTT on our marmoset
colony. Diazepam (0.25 mg/kg, i.m.) decreased the number of characteristic
body postures and increased the time spent in the front of the cage. The
second compound, modafinil (Modiodal) is a vigilance stimulant used as
treatment of narcolepsy. Oral administration of modafinil in a dose varying
from 50 mg/kg to 225 mg/kg reduced the anxiety-related behavior. No anxiolytic
effects of modafinil were found in earlier studies. The third compound
was ?9-tetrahydrocannabinol (?9-THC), the main euphorigenic component
of marijuana (Cannabis sativa), was administrated orally in doses of 2,
4 and 8 mg/kg. The display of postures was reduced after all three doses.
This anxiolytic effect was found earlier in other anxiety test systems
in other species.
In conclusion, this study showed that the human threat test is a sensitive
test to measure anxiety-related behavior and can be adapted to other marmoset
colonies with different housing situations. It is a good method to distinguish
between different effects on anxiety of psychoactive compounds.
Paper presented
at Measuring Behavior 2005
, 5th International Conference on Methods and Techniques
in Behavioral Research, 30 August - 2 September 2005, Wageningen, The
Netherlands.
© 2005 Noldus
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