Channel rhodopsins are expressed in pre- and post-synaptic neuronal elements.

<p>A-E: Examples of eYFP-positive (ChR2 expressing) neuronal elements in the striatum (A-E, from monkey G) and VL (F, G, from monkey L). H and I: Proportion of immunolabeled elements in Putamen and VL. Scale bars: A-B, 0.25 µm; C-G: 0.5 µm. Abbreviations: d, dendrite; M. axons, myelinated axons; s, spine; U. axons, unmyelinated axons; t, terminal; u.i. or Unid., unidentified elements.