Figure 6.

PV⁺ interneuron autapses. A, Example of an autapse on the interneuron soma (2-month-old pair MK190115-1). Volume reconstructions of the interneuron (streptavidin Alexa-594) on top and serial sections through the autapse on the bottom. The fluorescence intensity of the axon is much weaker compared with that of the soma or dendrites. In the color map of the autapses, magenta outline represents the presynaptic bouton and black represents the postsynaptic target. B, Example of an autapse on a proximal dendrite (1-month-old pair MK181212). C, Developmental changes in the number of autapses per PV⁺ interneuron. Magenta circles represent neuronal pairs with postsynaptic interneuron. D, Example of an autapse (white arrow) at P14 (pair MK190405-1). Volume reconstruction of the interneuron only (left, streptavidin Alexa-594) and zoomed in view of the synapse with the interneuron in magenta and synapsin immunolabel in blue (right). Right, Inset, Single section through the autapse showing the colocalization of synapsin (blue) and the presynaptic bouton fluorescence (magenta). E, Developmental changes in the autapse target distribution. Magenta circles represent neuronal pairs with postsynaptic interneuron. C, F, There is no statistically significant difference depending on age as determined using one-way ANOVA. Middle lines indicate the medians. Box limits indicate the 25th and 75th percentiles as determined by R software. Whiskers extend 1.5× the interquartile range from the 25th and 75th percentiles. Dots represent outliers. Crosses represent sample means. Data points are plotted as open circles.