Abstract
Glucagon-like peptide 1 receptors (GLP-1R) are expressed in the lateral septum (LS) of rats and mice, and we have published that endogenous LS GLP-1 affects feeding and motivation for food in rats. Here we asked if these effects are also observed in mice. In separate dose-response studies using male C57Bl6J mice, intra-LS GLP-1 or the GLP-1R antagonist Exendin 9 (Ex9) was delivered shortly before dark onset, at doses subthreshold for effect when injected intracerebroventricularly (icv). Intra-LS GLP-1 significantly suppressed chow intake early in the dark phase and tended to reduce overnight intake. However, blockade of LS GLP-1R with Ex9 had no effect on ad libitum dark onset chow intake. We then asked if LS GLP-1R blockade blunts nutrient preload-induced intake suppression. Mice were trained to consume Ensure immediately before dark onset, which suppressed subsequent chow intake, and intra-LS Ex9 attenuated that preload-induced intake suppression. We also found that restraint stress robustly activates hindbrain GLP-1-producing neurons, and that LS GLP-1R blockade attenuates 30-min restraint stress-induced hypophagia in mice. Furthermore, we have reported that in the rat, GLP-1R in the dorsal subregion of the LS (dLS) affect motivation for food. We examined this in food-restricted mice responding for sucrose pellets on a progressive ratio (PR) schedule. Intra-dLS GLP-1R stimulation significantly suppressed, and Ex9 significantly increased, operant responding, and the Ex9 effect remained after mice returned to ad libitum conditions. Similarly, we found that stimulation of dLS GLP-1 suppressed licking for sucrose and conversely, Ex9 increased licking under ad libitum feeding conditions. Together, our data suggest that endogenous activation of LS GLP-1R plays a role in feeding in mice under some but not all conditions, and that these receptors strongly influence motivation for food.