The Effect of Astrocytic S100B Protein on Memory Conolidation Rats

Introduction: S100B is a protein released from astrocytes, which controls neuroglial relationship and probably plays a role in memory and synaptic plasticity. Study of the functional relationship between astrocytes and neurons is of great importance. The present study was conducted to evaluate the effect of S100B infusion into the CA1 region of the hippocampus, on memory performance in male rats. Methods: In this study, 40 male wistar rats were used. Animals were bilaterally implanted with indwelling cannulae in the CA1 region of the hippocampus. Seven days after surgery, animals were trained in a step-down passive avoidance task (0.5 mA, 100 Hz, 5 sec). Immediately after the training, animals received 0.5 μl infusion of saline or S100B (5, 50, 500, or 5000 ng) bilaterally. Twenty four hours later step-down first latency and total time spent on platform were measured as learning and memory indices. Results: The infusion of 5 ng S100B induced a significant increase in step-down first latency (p< 0.01), and also increased the total time spent on the platform compared to the control group (p < 0.001). Surprisingly, animals which received doses of 500 and 5000 ng showed a significant decrease in both indices compared to the control group (p< 0.001). Conclusion: Our findings indicate that astrocytic S100B protein has modulatory effects on memory, in a way that in nanogram doses facilitates, but in micrograms impairs memory in passive avoidance task.