Novelty suppressed feeding test

A modified version of the original novelty suppressed feeding test developed by Britton and Britton⁴² was used in which mice were tested under ad libitum conditions. A similar test was recently described by Lockie et al.⁴³ to demonstrate that peripheral ghrelin increases food motivation in an anxiogenic environment. Mice were given access to a palatable snack (either Pilsbury™ cookie dough or a 60% high fat diet pellets (Harlan)) for 48 h and this was removed from the home cage 24 h before the novelty suppressed feeding test. At all times the mice consumed all of the palatable food provided, showing a preference for this diet. After the open field test (see above), each experimental mouse was briefly removed from the open field and a dish containing the palatable snack to which they had been previously exposed was placed in the middle of the open field. The mice were then placed back into a corner of the open field and were videotaped for 5 min to measure the latency to approach the food and the number of food approaches during the test. The quantity of palatable food consumed was measured at the end of the test.

To ensure that the order of tests did not influence behavioral performance, tests were administered 7 days apart in a counterbalanced order. Thus, half of the mice in each group underwent the social interaction test on test day 1 first, and the open field test immediately followed by the novelty suppressed feeding test first on test day 2. The order of test presentation was reversed for the remaining mice. Mice were tested under ad lib conditions in all experiments. The behavioral scoring of videos was done blind to the conditions by two independent raters with a correlation of 0.93 in their score ratings.