P.2.a.012 Co-administration of fluoxetine with acetylsalicylic acid, but not flurbiprofen or celecoxib, for one week shows an antidepressant-like effect

Increasing evidence is now demonstrating the involvement of the immune system and in particular of their effectors, cytokines, in the development and progression of depression. In particular, it is worth underlying how pro-inflammatory cytokines appear to be increased in blood or brain of patients with major depression (MD) and that pharmacological use of pro-inflammatory cytokines (i.e. interferon alpha) may induce MD. These data suggest a role for inflammation in the pathogenesis of depression and that anti-inflammatory drugs may be used as an adjunctive therapy in the treatment of MD. However, some studies reported contradictory results and suggest that adverse effects may contraindicate the use of anti-inflammatory agents in the treatment of depression. Nevertheless, non-steroidal anti-inflammatory drugs (NSAIDs) can have different mechanisms of action also depending on the dose. This is true for the therapeutic effects as well as for the unwanted side effects. On this basis, the present study aimed at evaluating the behavioural effect of the co-administration of fluoxetine (FLX, 5 mg/kg i.p.) with different NSAIDs in the chronic escape model of depression (CED). The CED model of depression possesses face, construct and pharmacological validity and is based on the induction, and maintenance, of an escape deficit upon exposing rats to unavoidable stressors. We previously demonstrated that, in this model, the stress-induced impaired behaviour can be resolved by one week of treatment with the co-administration of FLX (5 mg/kg/i.p.) plus acetylsalicylic acid (ASA, 45 mg/kg i.p.) but not FLX alone [1]. Here we evaluated the effect of the co-administration of FLX and flurbiprofen (FLB, an inhibitor of Cox-1 and Cox-2, 5 mg/kg, p.o.) or celecoxib (CLX, a selective COX2 inhibitor, 5 mg/kg, p.o.) in the CED model after 7 days of treatment. The co-administration FLX plus ASA (45mg/kg i.p.) was used as a positive control. Morever we tested the behavioral effect of different doses (45, 22.5 and 11.25 mg/Kg i.p.) of ASA as potentiating agent of the effect of fluoxetine. Our study shows that only the co-administration of ASA with FLX reverted the stress-induced condition of escape deficit after 7 days of treatment. Moreover, the amplitude of the antidepressant-like effect was dose dependent. The percentage of the antidepressant response was about 90%, 60% and 40% for animals receiving FLX (5 mg/kg/i.p.) plus ASA at the dose of 45, 22.5 or 11.25 mg/Kg i.p. respectively. Both flurbiprofen and celecoxib, when administered together with FLX for 7 days, failed to induce an antidepressant-like effects in the CED model. Higher dose of FLB (50 mg/Kg p.o.) and CLX (20 mg/Kg p.o.) were also tested, but they were associated to high mortality rate (80% and 25% respectively). These data demonstrated that neither all NSAIDs, nor all doses, may be useful in the treatment of depression while adverse effects can be potentiated or induced by the co-administration with antidepressants. Unraveling the cellular and molecular mechanisms behind the dissimilar behavioral response elicited by different anti-inflammatory drugs can contribute to understand the role of inflammation in the etiopathogensis of MD and to improve patient care. [1] Brunello, N., Alboni, S., Capone, G., Benatti, C., Blom, J.M., Tascedda, F., Kriwin, P., Mendlewicz, J., 2006 Shortened onset of action of antidepressants in major depression using acetylsalicylic acid augmentation: a pilot open-label study. Int Clin Psychopharmacol. 21:227-31.