Behavioural effects of anxiogenic agents in the common marmoset.

The effects of the anxiogenic agents FG7142, caffeine, pentylenetetrazole, and amphetamine were assessed in two anxiety situations in the marmoset, first in an "anxiogenic" test based on the animal's response to a human observer standing in front of the home cage and second in a low-anxiety situation where animals behaviour was videotaped in the absence of the observer. In response to the human observer, the anxiolytic agent diazepam (0.1-2.5 mg/kg, SC) was shown to reduce the intensity of behaviours such as postures, while increasing time spent on the cage front. In this test, with the exception of amphetamine, which only modified responding at stereotypic doses, the anxiogenic agents failed to modify marmoset behaviour. In contrast, in the low-anxiety filming protocol the anxiogenic agents consistently reduced measures of locomotor activity while increasing the amount of time animals spent in the nest box. It is suggested that the low-anxiety protocol may be useful to evaluate drug-induced anxiogenesis and in studies of withdrawal from chronic anxiolytic treatment or drugs of abuse.