Figure 2. Cell-type-specific integrated analysis of physiological properties, anatomical parameters and nanoscale molecular imaging.
(a) Representative voltage traces in response to depolarizing and hyperpolarizing current steps recorded in whole-cell patch-clamp configuration from a multipolar neuron in CA1 stratum radiatum shows the characteristic accommodating, regular-spiking pattern. (b) The neuron was filled with biocytin during recording to allow post-hoc reconstruction. While the dendrites (blue) arborize in all hippocampal layers, the axon cloud (red) is restricted to the stratum pyramidale. (c) Measurement of the relative laminar location of the recovered axonal varicosities confirms a bouton distribution biased towards the pyramidal layer. The bouton distribution index (BDI) based on the descriptive statistics of the distance distribution classifies this cell as a perisomatic interneuron (BDI > 1). (d) Maximum intensity projection of a deconvolved confocal stack of the biocytin-filled axon terminals. (e,f) Subsequent STORM superresolution imaging reveals CB1-immunolabeling on the identified boutons. (f) This STORM image depicts CB1 receptor localization points within the axon terminal shown in the boxed region in d2. (g) Traces recorded from another interneuron also show accommodating firing pattern. (h) This multipolar interneuron exhibits a distinct axonal morphology from the cell presented in b. (i) BDI classifies this cell as a dendritic interneuron (BDI < 0.5). (j-l) Combined confocal/STORM imaging visualizes the nanoscale distribution of CB1 receptors in identified boutons of the same dendritic interneuron. Boutons were imaged at a similar tissue depth (~5 μm) to equalize antibody penetration probability and the impact of light scattering. Throughout the present study, we have processed and evaluated 80 interneurons in the same manner.