“…Light from single-cell transcriptomics is now beginning to illuminate dark corners of cellular neuroscience 424 that have long resisted mechanistic and functional analysis (Fan et al, 2018;Fishell and Kepecs, 2019; may be one such corner. While profound impacts of neuropeptide signaling are well-established in a wide 428 range of non-mammalian and sub-cortical neural structures (Borbély et al, 2013;Burbach, 2011;Elphick 429 et al, 2018;Grimmelikhuijzen and Hauser, 2012;Katz and Lillvis, 2014;Kuffler et al, 1979) and there 430 certainly is an excellent literature on cortical neuropeptide signaling (Crawley, 1985;Férézou et al, 2007;431 Gallopin et al, 2006;Gomtsian et al, 2018;Hamilton et al, 2013;Liu et al, 2018;Mena et al, 2013;Mitre 432 et al, 2018;Owen et al, 2013;Rossier and Chapouthier, 1982;Williams and Zieglgänsberger, 1981), 433 published physiological results are surprisingly rare given the breadth of neuroscientific interest in cortex.…”