Figure 4.
Systemic LiCl decreases electrically-evoked dopamine release via central GLP-1 receptors in awake rats. (a) Time-dependent effects of treatments. After three baseline stimulations, rats were either pretreated (lateral ICV) with Ex-9 (broken lines) or vehicle (veh; solid lines). Following an additional four stimulations, rats were injected (IP) with either LiCl (red) or vehicle (black). Data are expressed as % of baseline dopamine concentration evoked by electrical stimulation of the VTA once every 5 min. Data points represent group means and error bars are±1 standard error of the mean (SEM). (b) Statistical comparison of the average % change in dopamine concentration from baseline at the 60-minute post-LiCl (red) or vehicle (black) time point demonstrates a significant (*p<0.05) decrease in dopamine concentration in the animals that received LiCl treatment after vehicle pretreatment (n=5; solid red bar) relative to animals that received LiCl treatment after Ex-9 pretreatment (n=5; stippled red bar) or vehicle treatment after either vehicle (n=5; solid black bar) or Ex-9 (n=5; stippled black bar) pretreatment. Error bars indicate mean±SEM. (c) NAc recording sites depicted as circles (black filled= vehicle/vehicle, red filled= vehicle/LiCl, black crosshatched= Ex-9/vehicle, red crosshatched= Ex-9/LiCl) on coronal sections modified from Paxinos and Watson (2007). Numbers on the left indicate approximate distance from bregma.