MONITORING RELEASE OF NEUROTROPHIC ACTIVITY IN THE BRAINS OF AWAKE RATS

Intracerebral microdialysis of awake rats was used to monitor the poss ible release of neurotrophic factors from brain cells in response to i njury and excitation. Perfusates were tested with ganglia bioassays an d enzyme immunoassay. Trophic activity was released after implantation of the microdialysis probe into the hippocampus but not into the stri atum, as assessed by increased nerve fiber outgrowth from Remak's gang lion. Kainic acid treatment significantly increased the release of tro phic activity from hippocampal sites. These findings suggest that the brain responds to mechanical injury as well as to certain excitatory s timuli by regional extracellular release of neurotrophic activity that is not identical to the actions of known neurotrophic factors.