Fig. 1: Transsynaptic modulation.
From: Selective control of synaptically-connected circuit elements by all-optical synapses
a Cell A connects with cells B, C, D and E; however, only cell A’s communication with cell B should be modulated, either amplified or dampened. b If cell A expresses optogenetic actuators, restriction of a light beam to the area of intended synaptic transmission can minimize unwanted activation (cell E will not be activated), but the likelihood of still activating unwanted synapses (cells C and D) is high. c The same applies when expressing a chemogenetic actuator (DREADD, designer receptor exclusively activated by designer drugs) in cell A and restricting application of the ligand CNO (Clozapine-N-Oxide) to an anatomical area as small as possible. d True cell-to-cell synaptic communication can be achieved by expressing a luciferase in cell A and an opsin in cell B. Activity of neuron A and application of the luciferin CTZ (Coelenterazine) results in light emission at all synapses of A, but only the opsin-expressing cell B will be modulated. At the same time, opsin-expressing cells not synaptically contacted by the luciferase-expressing cell A will not be modulated.
