POTENT OPTOGENETIC SUPPRESSION OF NEUROTRANSMITTER RELEASE BY PDCO IN THE MOUSE NEOCORTEX IN VIVO

Even relatively simple behaviors are orchestrated by distributed neural ensembles that span various brain regions. Comprehending how long-range connections link these ensembles requires methods that can selectively manipulate their function. Although optogenetic approaches can control neuronal firing with high spatiotemporal precision, many projection neurons send branched axon collaterals to multiple downstream targets, resulting in only a partial—and potentially misleading—view of a pathway’s contribution to circuit function. Optogenetic actuators acting directly on the synaptic release from long-range projections with high temporal precision are therefore desirable to provide a more fine-grained understanding of the role of specific neuronal pathways. Recent progress in developing light-activated G-protein couple receptors (GPCR) revealed that the Platynereis dumerilii ciliary opsin (PdCO) is an inhibitory bistable optoGPCR that can efficiently silence synaptic transmission with high spatial and temporal precision (Wietek et al., Nature Methods, 2024). Here, we further characterized PdCO’s ability of silencing synaptic transmission in vivo, examining the well-established monosynaptic pathway from whisker primary somatosensory barrel cortex (wS1) to the whisker primary motor cortex (wM1). We used a viral approach to express PdCO in excitatory neurons of wS1, together with a soma-targeted light-activated cation channel ChrimsonR. Optogenetic stimulation of wS1 neurons evoked a short-latency response in wM1 measured with local field potentials or whole-cell patch-clamp recordings of membrane potential. Activation of PdCO by applying light to frontal cortex reversibly and potently blocked the evoked response in wM1, suggesting that PdCO might be a powerful tool to dissect circuit function in behaving mice.