Transcriptomically-guided pharmacological experiments in neocortical and hippocampal NPY-positive GABAergic interneurons

Cortical GABAergic interneurons have been shown to fulfil important roles by inhibiting excitatory principal neurons. Recent transcriptomic studies have confirmed seminal discoveries that used anatomical and electrophysiological methods highlighting the existence of multiple different classes of GABAergic interneurons. However, individual studies have rarely addressed regional specific differences in gene expression in a given subclass of neuron. Using single-cell Patch-RNAseq, we characterised neuropeptide Y (NPY)-positive GABAergic interneurons in superficial layers of the primary auditory cortex and in distal layers of area CA3. We found that more than 300 genes are differentially expressed in NPY-positive neurons between these two brain regions. For example, the AMPA receptor auxiliary subunit Shisa9/CKAMP44 and the 5-HT2a receptor are significantly higher expressed in auditory NPY-positive neurons. These findings guided us to perform pharmacological experiments that revealed a role for 5-HT2a receptors in auditory NPY-positive neurons. Specifically, although the application of 5-HT led to a depolarisation of both auditory and CA3 NPY-positive neurons, the 5-HT2a receptor antagonist ketanserin only reversed membrane potential changes in auditory NPY-positive neurons. Our study demonstrates the potential of single-cell transcriptomic studies in guiding directed pharmacological experiments. 8 NPY-EGFP mice were analyzed for a total of 46 NPY positive cells and 1 NPY negative cell. For NPY positive cells, 21 were from the Hippocampal CA3, 20 from ACTX (auditory cortex), 3 from the Hippocampal CA1, and 2 from the Hippocampal DG. The NPY negative cell was from the Hippocampal CA3.