Anxiolytic-like profile in Wistar, but not Sprague-Dawley rats in the social interaction test

The social interaction test is a valuable behavioural model for testing anxiolytic drugs in rodents, quantifying the level of social behaviour between pairs of rats.

The aim of the present study was to assess the appropriateness of the social interaction test for use with a Sprague-Dawley rat line, because of increasing use of this strain in targeted mutagenesis research.

Sprague-Dawley and Wistar rats received either diazepam or mCPP or were exposed to different environmental conditions (lighting, social isolation prior testing, habituation, testing-time). General anxiety-related parameters measured were: duration of active social contact, frequency of active social contact, latency to first contact. Different forms of active social contact were recorded: number of crawls, follows and sniffs. Secondly, aversion-induced hippocampal serotonin release and serotonin content in brain regions were measured.

In Wistar rats habituation to the test substantially increased the time of social contact, an effect comparable with treatment with diazepam (1 mg/kg), whereas changes in the lighting level had less impact. Latency to the first contact increased under "anxiety-reducing" conditions, the frequency of contacts did not change consistently. Sprague-Dawley rats behaviour did not change under varying environmental conditions, and treatment with diazepam had only sedating effects at higher doses (5 mg/kg). Anxiogenic doses of mCPP caused reduced social interaction in both strains. Serotonin release and serotonin content were higher in the anxious Wistar rats.

Different rat strains as well as differing test conditions have a major impact on the outcome of this animal test for anxiety.