Fluoxetine induced insulin-like growth factor II (IGF-II) changes in hypothalami of normal, exercised and food restricted rats.

Hypothalamic and pituitary insulin-like growth factor II (IGF-II) peptide concentrations are differentially regulated by factors associated with metabolism such as insulin and glucoprivation. However, the effects of other metabolic stressors such as food restriction or exercise on hypothalamic IGF-II concentrations remain largely to be explored. In order to assess whether metabolic stress alters central nervous system IGF-II secretion, peptide analysis was conducted in rats exhibiting activity-based anorexia (ABA) compared to exercised-matched, body weight-matched or ad libitum fed controls. Further, the possibility of serotonergic control of IGF-II secretion was examined by determining IGF-II response to fluoxetine (FLX) injections (15 mg/kg body wt., i.p.). While ABA and body weight loss altered peripheral IGF-II concentrations compared to ad libitum fed or exercised controls, these treatments had no effect on hypothalamic or posterior pituitary IGF-II content. However, FLX administration increased IGF-II concentrations in the ventromedial hypothalamus and decreased IGF-II content in the lateral hypothalamus compared to vehicle injected. Anterior pituitary levels of IGF-II were also decreased by FLX. These data suggest that a serotonergic influence on CNS IGF-II exists and that IGF-II secretion may be altered by factors affecting serotonin metabolism or efficacy.