Centrally administered tumor necrosis factor-α facilitates the avoidance performance of Sprague–Dawley rats

In addition to their immunological functions, recent research has indicated that the pro-inflammatory cytokines can influence learning and memory processes. We have previously shown that a peripheral injection of TNFα facilitates the acquisition of a leverpress avoidance task 24 h post-injection. Because the improved acquisition is presumably mediated by central changes, the current experiment involved directly injecting TNFα into the third ventricle 24 h prior to training. The data indicate that low (20 ng) but not high (40 ng) doses of TNFα produced improved avoidance performance. Results are discussed in terms of possible monoaminergic sensitization induced by TNFα and the relationship of this to acquisition of the avoidance response.