The thyroid hormone derivative 3-iodothyronamine increases food intake in rodents

Abstract

Background: The thyroid hormone derivative 3‐iodothyronamine (T₁AM), an endogenous biogenic amine, is a potent agonist of the G protein–coupled trace amine‐associated receptor 1 (TAAR1). T₁AM is present in rat brain, and TAAR1 is expressed in hypothalamic nuclei associated with the regulation of energy homeostasis. Aim: The aim of this study was to determine the effects of T₁AM on food intake in rodents. Methods: We determined the effect of (i) intraperitoneal (i.p.) administration of T₁AM on food intake, oxygen consumption (VO₂) and locomotor activity in mice; (ii) intracerebroventricular (ICV) injection of T₁AM on food intake in male rats; (iii) c‐fos expression following ventricular administration of T₁AM in male rats; and (iv) direct injection of T₁AM into the arcuate nucleus (ARC) of male rats on food intake. Results: (i) T₁AM (4 nmol/kg) significantly increased food intake following i.p. injection in mice but had no effect on VO₂ or locomotor activity. (ii) ICV administration of T₁AM (1.2 nmol/kg) significantly increased food intake in male rats. (iii) Intraventricular administration of T₁AM significantly increased c‐fos expression in the ARC of male rats. (iv) Direct administration of T₁AM (0.12, 0.4 and 1.2 nmol/kg) into the ARC of male rats significantly increased food intake. Conclusion: These data suggest that T₁AM is an orexigenic factor that may act through the ARC to increase food intake in rodents.