Perinatal asphyxia results in changes in presynaptic bouton number in striatum and cerebral cortex - a stereological and behavioral analysis

Deficits in cognitive function have been related to quantitative changes in synaptic population, particularly in the cerebral cortex. Here, we used an established model of perinatal asphyxia that induces morphological changes , i.e. neuron loss in the cerebral cortex and striatum, as well as behaviou ral deficits. We hypothesized that perinatal asphyxia may lead to a neurode generative process resulting in cognitive impairment and altered presynapti c bouton numbers in adult rats. We studied cognitive performance at 18 mont hs and presynaptic bouton numbers at 22 months following perinatal asphyxia . Data of the spatial Morris water escape task did not reveal clear memory or learning deficits in aged asphyctic rats compared to aged control rats. However, a memory impairment in aged rats versus young rats was observed, w hich was more pronounced in asphyctic rats. We found an increase in presyna ptic bouton density in the parietal cortex, whereas no changes were found i n striatum and frontal cortex in asphyctic rats. An increase of striatal vo lume was observed in asphyctic rats; leading to an increase in presynaptic bouton numbers in this area. These findings stress the issue that volume me asurements have to be taken into account when determining presynaptic bouto n density. Furthermore, perinatal asphyxia led to region-specific changes i n presynaptic bouton numbers and it worsened the age-related cognitive impa irment. These results suggest that perinatal asphyxia induced neuronal loss , which is compensated for by an increase in presynaptic bouton numbers. (C ) 2000 Elsevier Science B.V. All rights reserved.