Interneuronal connections are an important component of the integration circuits of the hippocampus. They are formed mostly postnatally, i.e. in a phase when their development can be strongly influenced by external environmental factors. In model postnatal hypoxia, a morphometric analysis showed reduction of the number of dendritic segments (chiefly 3rd order segments) in 18-day-old rats. The total length of the dendrites was unaltered, but mean segment length increased. Interneuron density in the experimental animals was higher, especially in the stratum radiatum, but pyramidal cell density was lower than in the controls. These findings are evidence that hypoxia has a complex effect on the microstructure of the hippocampus and that, in the long run, it can lead to impairment of the balance of the elementary processes of excitation and inhibition.

Department of Physiology Faculty of Medicine Charles University Prague