Coronal slices of mouse embryonic forebrain at E14 were prepared as described above. Sections were transferred into tissue culture dishes containing complete HBSS for ~1 hour, after which CAG-Cav1.2 (WT– or TS–CACNA1C) plasmids were focally co-injected with CAG::GFP at a ratio of 1:0.5 directly into the ganglionic eminence through a glass micropipette. Cav1.2 overexpression constructs were generated by insertion of PCR-amplified WT– and TS–Cav1.2 coding sequences from dihydropyridine-insensitive Cav1.2 constructs39 into pCAGIG (kind gift from C. Cepko through Addgene, plasmid 11159)46. Slices were then electroporated using two horizontally oriented platinum electrodes powered by a BTX Square Pulse Electroporator, and placed onto cell culture membrane inserts for subsequent live imaging 48 hrs later as described below.
