Whole-cell recordings and optogenetic manipulation of GABAergic neurons in the barrel cortex of behaving mice

• Applicant: Professor Dr. Carl Petersen
• Subject Area: Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2010 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 141272880

Most neurons (~80%) within the neocortical microcircuit are excitatory and release glutamate onto postsynaptic target cells. Inhibitory GABAergic neurons form the remaining ~20% of neocortical neurons. The inhibitory GABAergic neurons of the neocortex display a wealth of different molecular, structural and electrophysiological features, but the functional correlates of this diversity have yet to be mapped in behaving animals. Here, we propose to measure and perturb the membrane potential of different genetically-defined types of GABAergic neurons in L2/3 of mouse barrel cortex during quantified whisker behaviour. We will study mouse lines expressing Cre-recombinase in specific subtypes of GABAergic neurons, allowing visualisation of the Cre-expressing cell-types through Cre-dependent expression of fluorescent proteins and optogenetic manipulation through Cre-dependent expression of channelrhodopsin-2, halorhodospin or archaerhodopsin. We have selected to study mouse lines expressing Cre-recombinase from the gene loci of parvalbumin, somatostatin, vasoactive intestinal peptide and neuronal nitric oxide synthase. These four Cre-driver mouse lines are expected to label largely non-overlapping classes of neurons and account for most, although not all, of the GABAergic neurons in L2/3 mouse barrel cortex. We will study the membrane potential dynamics of these neuronal cell-types during quiet wakefulness, whisking, passive whisker stimulation, active touch, and during a simple detection task in which the mouse must lick for reward in response to a whisker deflection. Having measured the cell-type specific membrane potential correlations with whisker behaviour, we will next optogenetically manipulate each of the genetically-targeted neuronal classes while recording membrane potential. By activating or inhibiting a specific class of GABAergic neuron, we will perturb the neocortical neuronal network, which will help to determine the functional role of each of these genetically-defined types of GABAergic neurons. We will further examine if the optogenetic manipulations affect behaviour. Taken together, these experiments will substantially advance causal understanding of the functional operation of GABAergic neurons within the L2/3 barrel cortex microcircuit.

• DFG Programme: Research Units
• Subproject of: FOR 1341: Barrel Cortex Function
• International Connection: Switzerland