THE EFFECT OF CORTICOSTERONE IN RATS SUBMITTED TO THE ELEVATED PLUS-MAZE AND TO PENTYLENETETRAZOL-INDUCED CONVULSIONS

1. In order to examine the effects of corticosterone in the anxiety re sponse, the effect of acute, subchronic and chronic corticosterone (CO RT) administration were studied using two animal models to study using two animal models to study anxiolytic effects of drugs: the elevated plus-maze and the blockade of pentylenetetrazol (PTZ)-induced clonic c onvulsion. 2. The results obtained with the plus-maze showed an increa se in the percentage of open arm entries and time spent in the open ar ms after acute treatment with the CORT. These results may be interpret ed as an anxiolytic effect of corticosterone. Three days of vehicle tr eatment followed by an acute CORT administration, produced results tha t should also indicate anxiolytic effect of the corticosteroid. No eff ect was seen after 14 days of vehicle treatment followed by an acute C ORT injection. Subchronic or chronic CORT treatment did not produce re sults different from controls. CORT treatment did not affect the PTZ-i nduced clonic convulsion. 3. In conclusion these results suggest that the acute anxiolytic effect observed in the elevated plus-maze did not occur after repeated CORT administration or mild stressors. Moreover they also suggest that the anxiolytic effect did not involve GABA mech anisms.