AN INCREASED INTENSITY OF N-METHYL-D-ASPARTATE (NMDA) BUT NOT NON-NMDA RECEPTOR ACTIVATION MAY BE RESPONSIBLE FOR THE ENHANCEMENT OF EXCITATORY PROCESSES IN THE NEOCORTEX OF 2-WEEK-OLD RATS - A BRAIN-SLICES STUDY

During the brain maturation a critical period is detectable when the s ensitivity of the neocortex is high. Enhanced excitatory activity is c haracteristic at that time while the inhibitory processes are underdev eloped. The goal of this study was to determine the effectiveness of d ifferent types of excitatory amino acid antagonists reducing the elect rically evoked excitatory synaptic responses of the somatosensory cort ex. Effects of the specific competitive N-methyl-D-aspartate (NMDA) an tagonist 4-amino-phosphono-valerate (APV), and the specific non-compet itive, non-NMDA antagonist carbamoyl-7,8-methylenedioxy-5H-2,3-benzodi azepine (GYKI 53655) were analysed on neocortex slices prepared from 2 -week-old and adult rats. APV caused a partial inhibition of the elect rically evoked response more effectively in young animals than in adul ts, while the effective IC50 values were similar. In contrast, the non -NMDA antagonist had a similar effect on the slices of both age-groups .