[Is there solid evidence for reorganization of the neural network associated with development of behavioral...

Behavioral sensitization or reverse tolerance induced by repeated treatment of psychostimulants, such as amphetamine and cocaine, has been widely used as an animal model for schizophrenia. This phenomenon may result from almost eternally lasting plastic functional adaptation in the brain. Such long-lasting plasticity must accompany anatomical and morphological neural changes. Histological studies revealed that chronic treatment of psychostimulants induced thickness, elongation and an increased branch number of neurites and dendrites in cortices and accumbens, and an increased spine density. These changes may seem a positive adaptation for neural transmission, however, similar histological changes were seen after toxicity of methamphetamine as deafferation compensation. Therefore, further studies are needed to establish the significance of these morphological changes induced by chronic psychostimulants. On the other hand, neuromolecular studies showed increased phosphorylation of neuromodulin, increased expression of tissue-type plasminogen activator, synaptotagmin IV and arc, which are assumed to play roles in neural outgrowth and synaptogenesis. Although all of these histological and neuromolecular findings may suggest reorganization of the neural network should grow along with behavioral sensitization, more solid evidence is indispensable to confirm it.