Supplemental Fig. 7 from To eat or not to eat: ontogeny of hypothalamic feeding controls and a role for leptin in modulating life-history transition in amphibian tadpoles

The anorexigenic action of leptin develops during tadpole metamorphosis. We gave i.c.v. injections of 0.6% saline or rxLeptin (20 ng/g*BW) at two stages of tadpole metamorphosis, premetamorphosis (NF stage 50) or late prometamorphosis (NF stage 58) and measured feeding behavior as described in the Materials and Methods. We conducted 3-4 feeding trials per developmental stage and injection treatment, with each trial having four tanks per treatment (10 tadpoles per tank; the replicate was feeding trial; points represent the mean±SEM; n=3-4/time point). Tadpoles were randomly distributed throughout the tank before addition of food to quadrant A. They remained randomly distributed over the 15 minute measurement period if no food was added (the positions of animals in the tank were scored at 1 minute intervals) (p>0.05; Linear regression: Least squares). After the addition of food to quadrant A, there were more tadpoles in this quadrant over the 15 minute measurement period in the saline-injected NF stage 50 (p<0.0001) and NF stage 58 (p<0.0001), and rxLeptin-injected NF stage 50 (p<0.0001) treatments compared to the no food treatments. By contrast, rxLeptin treatment of NF stage 58 tadpoles strongly suppressed the directed movement into quadrant A after the addition of food; i.e., there was no difference between the no food and food added curves (p=0.897).