Glucocorticoids modulate the NGF mRNA response in the rat hippocampus after traumatic brain injury

Nerve growth factor (NGF) expression in the rat hippocampus is increased after experimental traumatic brain injury (TBI) and is neuroprotective. Glucocorticoids are regulators of brain neurotrophin levels and are often prescribed following TBI. The effect of adrenalectomy (ADX) and corticosterone (CORT) replacement on the expression of NGF mRNA in the hippocampus after TBI has not been investigated to date. We used fluid percussion injury and in situ hybridisation to evaluate the expression of NGF mRNA in the hippocampus 4 h after TBI in adrenal-intact or adrenalectomised rats (with or without CORT replacement). TBI increased expression of NGF mRNA in sham-ADX rats, but not in ADX rats. Furthermore, CORT replacement in ADX rats restored the increase in NGF mRNA induced by TBI. These findings suggest that glucocorticoids have an important role in the induction of hippocampal NGF mRNA after TBI.