INTRODUCTION: Optogenetics allows to stimulate selected neuronal populations with high temporal resolution but the spatio‑temporal extent of resulting effects is not well characterized. AIM(S): Experiment were aimed to evaluate spatial distribution of the potentials and currents evoked by light impulses in the channelrhodopsin-transfected rat cortex. METHOD(S): Rats were injected with viral vector introducing ChR2 into large portion of somatosensory cortex. 2–3 weeks later we performed acute in vivo experiments recording multichannel local field potentials evoked (EP) by a blue light delivered either to the cortical surface (surf-stim) or into the cortex (deep-stim). We analyzed spatio-temporal patterns of EPs and their 2-D current source density (CSD) profiles (kernel CSD method, https://github. com/Neuroinflab/kCSD‑python). RESULTS: Our preliminary results indicated that light evoked potentials consisted of early waves, resulting from opening ChR2 channels, overlapping with later components related to the synaptic spread of activity within cortical network. As expected, largest EPs were recorded close to the fiber tip, in layer 2–3 with surf‑stim and layer 5 with deep-stim. Longer impulses (10 ver 1 ms) evoked around 20% stronger responses. Up to 600–800 µm from a light source EPs sustained ~50% of max amplitude. However, CSD analysis indicated that after surf-stim the early current sink (1–2 ms) was restricted to ~400 µm in layer 2–3. Later, postsynaptic sink developed at 5–8 ms in layer 5. Later components had wider lateral spread across few columns with clear reflection of cortical layering. After intra-cortical light delivery activity seemed to spread within, not across the cortical columns. CONCLUSIONS: For well controlled use of optogenetics it is not enough to ensure light beam of sufficient strength. The localization of the fiber tip can have specific impact on the activity developing within local neuronal network. FINANCIAL SUPPORT: Supported by Polish National Science Centre grant 2013/08/W/NZ4/00691.
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.