Effects of anxiolytic and antidepressant drugs on long-lasting behavioural deficits resulting from one short stress experience in male rats

Exposure of male Wistar rats to one single session of ten inescapable footshocks induces changes in the behavioural responses to environmental stimuli as measured in the noise test 14 days later. Shocked (S) rats showed decreased locomotion and rearing during the first 3 min of exposure to a novel environment compared to control (C) rats. When the 85 dB background noise was switched off a marked immobility response emerged in S rats, concomitant with a further decrease in locomotion and rearing. In response to noise off, C rats showed hardly any immobility and a much smaller reduction in locomotion and rearing compared to S rats. These long-lasting changes in behaviour were not reversed by acute treatment with the antidepressants fluvoxamine (3.0–30.0 mg/kg) and desmethylimipramine (DMI, 2.5–10.0 mg/kg) injected IP 30 min before the noise test on day 14 following the shock session. Chronic treatment (day 1 to day 14) with flvoxamine or DMI did not reverse the behavioural deficits induced by shock exposure. Diazepam (0.6–5.0 mg/kg) administered acutely only reversed the effects of shock on locomotion during the first 3 min of the noise test. Chronic treatment with diazepam normalized the shock-induced decrease in locomotion and attenuated the rearing decrease during the first 3 min of the test, and partially restored shock-induced changes in behavioural response to switching off the noise. The most potent drug in this study was the 5-HT_1A receptor agonist flesinoxan (0.3–3.0 mg/kg). Both acute and chronic drug treatment were equally effective in reversing the shock-induced locomotion deficits as well as the marked immobility response in S rats, although rearing was not reversed. However, flesinoxan also increased locomotion and reduced rearing in C rats, suggesting some nonspecific stimulating effects of flesinoxan. In conclusion, the footshock-induced long-lasting behavioural changes are sensitive to treatment with (putative) anxiolytic agents, whereas no beneficial effect of the antidepressant drugs was found.