Serotonergic regulation of galanin-induced selective macronutrient intake in self-selecting rats.
We investigated macronutrient intake after intraventricular injection of galanin (GAL, 3 nmol/5 microl/rat) and/or serotonin (5-HT, 50 nmol/5 microl/rat) in self-selecting fasted rats with preferences for either carbohydrates or fats. GAL injection significantly increased carbohydrate and total intake in all rats irrespective of macronutrient preference, whereas 5-HT alone did not affect macronutrient intake. The GAL-induced increase in total intake decreased to the level of saline controls when GAL was coinjected with 5-HT. The ratio of kilocalories of carbohydrates, fats and proteins (macronutrient energy ratio) after injections of GAL and/or 5-HT was similar to the saline control. In carbohydrate-preferring rats, GAL increased carbohydrate, protein and fat intake as well as total intake. Coinjection of GAL and 5-HT tended to decrease carbohydrate intake, but increase protein and fat intake. The macronutrient energy ratio after injection of GAL did not change, but the carbohydrate energy ratio decreased after 5-HT was injected, with or without GAL. In contrast, in fat-preferring rats, GAL significantly increased carbohydrate intake. Injection of 5-HT with or without GAL did not change total macronutrient intake. The macronutrient energy ratio did not change after GAL injection with or without 5-HT. These differences suggest that macronutrient preferences should be considered in any macronutrient intake study, and that serotonergic neurons play a part in the regulation of GAL-induced macronutrient intake.
Tanaka
Michiko
M
Department of Food Sciences and Nutritional Health, Kyoto Prefectural University, Kyoto, Japan.
Kido
Yasuhiro
Y
D000818:Animals; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004041:Dietary Fats / Q000008:administration & dosage; D004044:Dietary Proteins / Q000008:administration & dosage; D002149:Energy Intake / Q000187:drug effects* / Q000502:physiology; D005215:Fasting / Q000502:physiology; D005518:Food Preferences / Q000187:drug effects / Q000502:physiology; D019004:Galanin / Q000008:administration & dosage* / Q000502:physiology; D007276:Injections, Intraventricular; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000008:administration & dosage* / Q000502:physiology
D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins; D012701:Serotonin; D019004:Galanin