Effect of ARC-directed leptin receptor gene therapy on hindbrain c-Fos induction by CCK. Mean number of cFLI-positive nuclei per section in the AP (A) or NTS (B) as determined by immunohistochemistry after i.p. injection of either saline vehicle (white bars) or a 1.0-μg dose of CCK (black bars) 7 days after adenoviral microinjection of either Ad-GFP (in Fa/Fa or fa^k/fa^k rats) or Ad-LEPR-B–GFP (in fa^k/fa^k rats). *P < 0.05, vehicle vs. CCK; P < 0.05, CCK treatment in Fa/Fa Ad-GFP and fa^k/fa^k Ad-LEPR-B–GFP vs. fa^k/fa^k Ad-GFP–treated rats.