Figure 4. In-vivo 2-photon imaging of GFP-labeled basket interneurons in Pv-cre mice.

(a) Low-magnification projection of a z-series starting at ∼20 µm below the pia surface to a depth of ∼120 µm, from a densely labeled area. The asterisks indicate the tops of two cell bodies. Numerous dendritic branches are indicated by blue arrows. (b–c) Higher magnification z-projections of regions highlighted in (a) at two different depths: 85–90 µm (b) and 65–75 µm (c) below the pia. Note the smooth, aspiny dendrites (blue arrows), and dense cluster of boutons of varying size (yellow arrowheads). (d) Projection of a z-series 60–170 µm below the pia from a sparsely labeled area, showing an isolated GFP-labeled basket interneuron. Dendrites (blue arrows) could be traced back to soma, and axonal boutons (yellow arrowheads) appear as a cloudy signal at this magnification. (e–f) Examples of axon morphology magnified from areas indicated by gray boxes in (d). (e) shows an axonal basket-like structure (asterisk), and (f) shows a well-isolated axon branch (yellow arrow) with distinct boutons (yellow arrowheads). (g–h) dendrite structures from areas indicated in (d). Dendrites of the cell were largely aspiny (g), though occasionally small protrusions were visible on some dendritic branches (h). Scale bars a,d: 20 µm; b–c, e–h: 5 µm.