CCK and infection: We were also able to drive expression of GCaMP in AON-OB projection neurons via retrograde infection with the same virus after injection into the OB of young (postnatal day 1–3) (7 mice) or adult Chrna7-Cre (2 mice) animals, as previously reported for cholecystokinin (CCK)-expressing neurons in AON (Rothermel et al., 2013).