Figure 2.

Cocaine self-administration is associated with increased plasma corticosterone levels and peripheral corticosterone administration increases activation of PPG-expressing neurons in the NTS. (a) Total active lever responses (mean±SEM) are shown for cocaine-experienced rats and yoked-saline controls. (b) Plasma corticosterone levels were significantly different in cocaine-experienced rats when compared with yoked-saline controls (n=14 per treatment). *P<0.01 for total active lever responses and plasma corticosterone levels between treatments (unpaired t-test). (c) Representative immunofluorescent micrographs (× 10) showing activation of NTS GLP-1-producing neurons, as measured using double immunohistochemistry for PPG (green) and c-fos (red), was increased in rats treated with corticosterone (15 mg/kg, s.c.) vs vehicle. (d) High-magnification image (× 20) of the insert in (c) showing neuron colocalization of PPG and c-fos immunoreactivity in the NTS of a corticosterone-treated rat. Total percentages of c-Fos-positive (+) cells coexpressing PPG (e) and PPG-positive (+) cells coexpressing c-Fos (f) were significantly increased in the NTS of rats treated with corticosterone (n=4) compared with vehicle-treated controls (n=3); cc, central canal. A full color version of this figure is available at the Neuropsychopharmacology journal online.