The histograms quantify the γ-aminobutyric acid (GABA) content within PT-PUL terminals, their postsynaptic elements, and large cortical terminals with round vesicles (RL) in two cases (01-02, 02-04). Using the mean gold particle density overlying selected RL profiles +2 standard deviations as an upper threshold for GABA-immunonegative profiles (vertical dashed line in the graph, and a double-headed arrow along the X axis), we estimated the number of GABAergic and non-GABAergic PT-PUL terminal and their target elements in the PUL. For abbreviations, see list.