S100B infusion into the rat hippocampus facilitates memory for the inhibitory avoidance task but not for the...

Adult male Wistar rats were bilaterally implanted with indwelling cannulae in the hippocampus. Forty-eight hours after surgery, animals were habituated to an open-field box during 2 min, being tested 24 h later; next they were trained in a step-down inhibitory avoidance task (3.0 s, 0.4 mA foot-shock), being tested again 24 h later. Immediately after the training session of each task, animals received a 0.5-microl infusion of calcium-phosphate-buffered saline (PBS) and S100B (20, 200, 2000, or 20,000 nM). In the inhibitory avoidance task, animals infused with the two highest concentrations of S100B, 2 and 20 microM, obtained higher scores of retention relative to controls in the test session (p<0.05), and a trend toward an increase was observed in animals infused with 200 nM (p<0. 10). In both sessions of the habituation task, groups were not different regarding crossings, rearings, and time for leaving the first square (p>0.10). These results indicate that, in rats, post-training increased hippocampal levels of S100B right after training facilitate, in a dose-dependent way, long-term memory for an inhibitory avoidance task, but not for an open-field habituation.