Correlations and Discrepancies between Serum and Brain Tissue Levels of Neurotrophins after Electroconvulsive Treatment in Rats

Introduction The neurotrophin brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) are a central part of the molecular concepts on neuroplastic changes associated with stress, anxiety and depression. An increasing number of studies uses serum BDNF levels as a potential indicator for central nervous system alterations. Methods To analyze the relationship between brain tissue and serum BDNF and NGF levels, we used electroconvulsive shocks (ECS), an animal model of electroconvulsive therapy, and studied the temporal profile of neurotrophin expression in the hippocampus, prefrontal cortex and serum. 88 male Sprague-Dawley rats received single or serial ECS treatments and were killed between 3 hours and 14 days after the last treatment. Results: We found a 2.8-fold rise for BDNF(1.3-fold for NGF) in the prefrontal cortex, and a 2.2-fold rise (1.2-fold for NGF) in the hippocampus after 5 ECS sessions. The temporal expression profile and correlation analyses between tissue and serum BDNF indicate that BDNF crosses the blood-brain barrier. No such correlation was found for NGF. Discussion: The time course of central and peripheral BDNF changes may significantly differ. However, we demonstrate substantial evidence that it can be justified to measure serum BDNF levels with a time delay to monitor brain tissue neurotrophin alterations.