Fig. 1

Measurement of food intake and the 2-bottle preference test. a Protocol for the measurement of food intake before, during, and after l-histidine administration. The first 6 days are the training period of the feeding cycle with 12 h of food deprivation. Food intake was measured at 1, 3, 6, and 12 h after starting the feeding period. On day 7, rats were injected with l-histidine (i.p.) or saline (i.p.), and food intake was measured at 1, 3, 6, and 12 h after starting the feeding period. b Protocol for the two-bottle preference tests using quinine solution (0.05 mM) and distilled water (DW) before (3 days) and after (3 days) l-histidine or saline administration (i.p.)