The present study was undertaken to evaluate the effects on hippocampal vascular endothelial growth factor (VEGF) levels in rats when they experience hippocampal-depen-dent spatial learning via the Morris water maze (MWM) task. Rats underwent one of two different versions of the MWM: weak or intensive. After one day of intensive training, a highly sensitive enzyme-linked immunosorbent assay (ELISA) was used to measure VEGF protein levels in the hippocampus, cortex, and serum, and higher levels were found in the trained group compared to a naive control group. VEGF levels also increased in rats that swam only for durations equal to the intensive training periods. In contrast, rats trained under the weaker MWM paradigm for five days showed a decrease in hippocampal VEGF protein level. Mimicking increases in neuronal VEGF in the hippo-campus by direct infusion of VEGF into CA1 resulted in up-regulation of the phosphorylation of the cAMP respon-se element-binding (CREB) protein and the Ca2+/calmodulin- dependent protein kinases II (CaMKII). These results su-ggest that VEGF may be a physiological parameter involved in learning procedures that include physical activity.

Keywords: learning, morris water maze, VEGF