Effect of early decrease in the lesion size on late brain tissue loss, synaptophysin expression and functionality after a focal brain lesion in rats.

The purpose of the present study is to determine the effects of early decrease in the lesion size on late brain tissue loss, synaptogenesis and functionality after a focal brain lesion in rats. The lesion was induced either to the cortex using the photothrombotic ischemic stroke or to the striatum using the malonate poisoning model. The cortical and striatal lesions amounted to 66-80 mm(3) at day 1 post-lesion and were reduced by 50% after the acute administration of dipyridyl (a liposoluble iron chelator) and aminoguanidine (an inhibitor of the inducible nitric oxide synthase), respectively. Loss of histologically intact tissue and synaptophysin expression as an indicator of synaptogenesis were examined at day 35 post-lesion. Both types of lesion resulted in synaptophysin upregulation in contralateral and ipsilateral cortical areas. On the contrary, brain tissue loss was greater after the striatal (-17%) than the cortical lesion (-5%). Synaptophysin expression and tissue loss were not different between drug- and vehicle-treated rats. Moreover, a set of standard neurological tests revealed a difference in deficit between the both types of lesion, yet only in the acute post-lesion stage. However, it did not distinguish between vehicle- and drug-treated rats whatever the lesion location. Our results indicate that late histological endpoints measurements are not recommended to probe the potential neuroprotective properties of a drug administered within the acute post-lesion stage. They also suggest that inhibition of cytotoxic mechanisms involved in lesion growth is of no clinical interest when it cannot lead to a long-term histological protection and/or increased synaptogenesis.