It was reported that brain-derived neurotrophic factor (BDNF) plays an important role in developmental plasticity of the visual cortex and its expression is regulated in activity-dependent manner. Althogh it is known that protein kinases such as , extracellular signal-regulated kinase 1/2 (ERK1/2), protein kinase A (PKA) or calcium-calmodulin kinase type IV (CaMK IV) regulate BDNF level in vitro, it is not clear how these kinases regulate BDNF level in vivo. So we measured level of BDNF protein in the visual cortex of young rats treated with various kinase inhibitors or activators to examine the contribution of each kinase to BDNF level. Surprisingly, inhibition of PKA increased BDNF protein level. Inhibition of ERK1/2 or CaMK for 2 days induced no detectable change in the BDNF level. These results suggest that BDNF level in the visual cortex might be regulated by combination of various kinases by other untested pathway. Increase of BDNF by PKA inhibition may reflect accumulation of unreleased BDNF, suggesting a role of PKA in BDNF release. [Jpn J Physiol 54 Suppl:S211 (2004)]
