Figure 4

The distribution of inhibitory and excitatory inputs shifts with developmental stage. (A) The average percentage of stimulated sites that generated inhibitory post-synaptic currents (IPSCs) at various distances from the cell body for each age group. At all distances, the percentage of responding sites increased between P20 and P22 and P30 and P35, after which the percentages at all distances declined. The declines were most pronounced at greater lateral distances from the soma, implying a preferential elimination of longer-range inhibitory inputs. (B) Age-related changes in the origins of excitatory post-synaptic currents (EPSCs) with distance from the cell body. The average percentage of stimulated sites that generated EPSCs at different ages is generally similar to the pattern seen with IPSCs (A). The major difference is the retention of a significant number of inputs originating at >500 μm from cell bodies; these probably reflect long-range horizontal connections. Error bars = standard error of the mean.