Potential role of endogenous brain-derived neurotrophic factor in long-term neuronal reorganization of the superior colliculus after bilateral visualdeprivation

The role of the brain-derived neurotrophic factor (BDNF), the BDNF receptor (TrkB), and the glutamic acid decarboxylase (GAD(67)) after neonatal, bila teral nerve deafferentiation during postnatal development was investigated in the rat superior colliculus (SC). BDNF and GAD(67) mRNA expression were significantly increased in optic (Op) and intermediate gray (InG) layers at 5, 8, 15, and 21 days after birth, but not in adult animals. However, TrkB mRNA expression was not modified at any time tested. At 15 days, where cha nges in BDNF and GAD(67) mRNAs were more evident, an upregulation of the NM DAR(1A) mRNA glutamate receptor in the Op and InG, a modification in the pa ttern of synaptic zinc in the superficial layers of SC, and an increased sy naptophysin immunoreactivity in the Op was found. This indicates the existe nce of a synergic mechanism between BDNF and NMDA to determine refinement o f connections after the loss of visual input in SC. (C) 2001 Academic Press .