Reversal of stable behavioural modifications through NMDA receptor inhibition in rats

Effects of Long-Term Acetyl-L-Carnitine Administration in Rats—II: Protection Against the Disrupting Effect of Stress on the Acquisition of Appetitive Behavior

“…Rats selected on the basis of their failure to escape (0-3 escapes/30 trials), starting 48 h after the escape test: (1) were restrained for 10 min; (2) received 10 min of restraint plus four unavoidable shocks, 48 h after (1); (3) spent 20 min in the cage where the unavoidable shock had previously been administered, 48 h after (2). By repeating this procedure on alternate days, the escape deficit can be maintained in all rats (De Montis et al, 1995). No significant differences in the amount of daily food and water consumption or in the curve of body weight increase was ever observed between control and chronically stressed rats (data not shown).…”

Efficacy of an Hypericum Perforatum (St. John's Wort) Extract in Preventing and Reverting a Condition of Escape Deficit in Rats

“…The ED paradigm is a slight modification of the classical Learned Helplessness Syndrome which has already been described (De Montis et al 1995;Gambarana et al 1995a). In brief, the unavoidable shock session lasted 50 min.…”

“…Although several studies have investigated the possible mechanism of action of the antidepressant activity of H. perforatum extracts (Müller et al 1997Nahrstedt and Butterweck 1997;Chatterjee et al 1998;Laakmann et al 1998), no conclusive evidences on such activity have been reported either in humans or in animal models. Thus, we decided to assess the activity of a total extract of H. perforatum in three experimental models recently devised in our laboratory for the study of antidepressant treatments (Gambarana et al 1995a, De Montis et al 1995, Ghiglieri et al 1997.…”

“…The first model is an acute form of escape deficit (ED), the utilization of which is restricted to the evaluation of the protective activity of antidepressants on the behavioral sequelae of an unavoidable stress (Gambarana et al 1995a). The second is a chronic model of ED, which can be maintained indefinitely by the administration of tedious, mild stressors on alternate days (De Montis et al 1995), and which allows the study of ED reversal by antidepressant treatments (De Montis et al 1995). The third is a model of anhedonia based on the finding that repeated unavoidable stressors prevent the development of an operant appetitive behavior induced and maintained by a highly palatable food (vanilla sugar) in rats fed ad libitum (Ghiglieri et al 1997).…”

“…Second, the chronic ED condition, as maintained by the repeated stress paradigm, can be used to evaluate the revertant efficacy of a treatment (De Montis et al 1995). However, chronic ED is less reliable than the acute model for studying the mechanism of a drug's action by the use of selective receptor antagonists, because the effect of any antagonist administered acutely before the last stress session would be difficult to interpret.…”