Neurotrophic factor expression after focal brain ischemia preceded by different preconditioning strategies

BACKGROUND: Both prolonged brain ischemia and preconditioning (PC) induce expression of neurotrophic factors. However, the influence of PC on their expression after a long-term ischemia remains vague. Previously, we have found various effects of PC on mRNA levels of different cytokines after focal brain ischemia. Thus, we investigated mRNA expression of nerve growth factor, brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor after 90-min middle cerebral artery occlusion (MCAo) preceded by ischemic or chemical PC. METHODS: MCAo was induced in rats using the suture method. PC had been carried out 3 days earlier. There were 4 experimental groups: MCAo alone; ischemic PC and MCAo; chemical PC and MCAo, and sham-operated rats. Expression of mRNAs in the ipsi- and contralateral cortex was studied by semiquantitative RT-PCR at 12 and 24 h after MCAo. RESULTS: Despite clearly neuroprotective effects of both PC strategies, mRNA levels of neurotrophic factors were similar in tolerant and nontolerant rats. Only BDNF mRNA expression, 12 h after reperfusion, was lower when ischemic PC was applied prior to long-term ischemia. CONCLUSIONS: These results suggest that PC generally does not change the expression of neurotrophic factor expression after a long-term focal brain ischemia compared to the nontolerant state.