Effects of peripheral 5-HT on consumption of flavoured solutions.

Non-deprived rats, injected SC with serotonin (5-hydroxytryptamine; 5-HT), showed flavour-dependent alterations in fluid consumption during 2-h tests. The consumption of water, quinine, citric acid or saline was increased by 5-HT, whereas the consumption of sucrose, saccharin or milk was decreased. There were dose-dependent decreases in saccharin and milk consumption with maximal suppression of intake at 2 mg/kg. Two-bottle preference tests (flavour versus water) revealed that 5-HT increased saline consumption without changing saline preference and reduced consumption of, and preference for, both saccharin and sucrose. These results are discussed in terms of the characteristics which identify substances as being "food-like" rather than "water-like", and it is suggested that peripheral 5-HT plays a role in the control of both water and food intake. This latter function may be fulfilled through an alteration in the incentive value of food-related stimuli.