Social competition in dominant rats can be attenuated by anxiogenic drugs

In a previous study it was found that, in groups of three male Wistar rats competing for access to sweetened milk, access to the milk by subordinate animals was increased after administration of anxiolytic drugs. This result was consistent with the hypothesis that levels of social competition were associated with different levels of fear. The present study involved the administration of anxiogenic drugs to rats found to be dominant during similar social competition tests. Dose-related decreases in access to the milk during competition sessions were produced by FG 7142 (0.3-5.0mg/kg), pentylenetetrazole (0.6-10mg/kg) and yohimbine (1.0-4.0mg/kg). These three compounds were also investigated on the milk intake of the same animals tested singly. It was found that there was a wide separation between doses active in the two conditions with FG 7142 and pentylenetetrazole, but a much less wide separation with yohimbine. These results are further evidence that tests of social competition provide sensitive behavioural baselines for assessing the effects of drugs which modulate anxiety levels.