Hypothalamic monoaminergic activity in obese Zucker rats in response to acute and chronic dietary stimuli

S. E. Specter, J. S. Stern, Barbara A Horwitz

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Monoamine neuromodulators link diet-related signals with autonomic responses in the regulation of energy balance. In view of evidence that sympathetically mediated expenditure is blunted in genetically obese (fa/fa) Zucker rats, a central defect in neurochemical activity has been proposed. This study tested the hypothesis that genotypic differences in monoaminergic activity in the hypothalamus underlie a blunted sensitivity of fa/fa rats to acute and chronic dietary stimuli, leading to less effective modulation of energy metabolism. Homozygous lean and obese Zucker rats were fed a protein- restricted (PR, protein = 8% of total dietary energy) or control (CF, 21% protein) diet from the age of 5 wk. At 10 wk of age, postprandial oxygen consumption (thermic effect of food, TEF) and levels of brown adipose tissue (BAT) uncoupling protein were significantly elevated (P < 0.0005) in PR vs. CF lean rats. Serotonin turnover was significantly (P < 0.0014) greater in the ventromedial hypothalamus (VMH) of meal-fed lean PR (vs. CF) rats, consistent with the suggestion that VMH serotonin release stimulates sympathetic outflow and may signal a heightened drive for protein intake. Serotonergic activity, BAT uncoupling protein, and TEF were not elevated in PR obese rats in response to a test meal, supporting the view that activation of sympathetic outflow in response to diet-related stimuli in fa/fa rats is impaired.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Issue number4 33-4
StatePublished - 1996


  • brown adipose tissue uncoupling protein
  • protein restriction
  • serotonergic activity
  • sympathetic nervous system
  • thermic effect of food

ASJC Scopus subject areas

  • Physiology
  • Endocrinology
  • Biochemistry
  • Physiology (medical)


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