Serotonergic activity is depressed in the ventromedial hypothalamic nucleus of 12-day-old obese Zucker rats

V. H. Routh, J. S. Stern, B. A. Horwitz

Research output: Contribution to journalArticlepeer-review

32 Scopus citations


We previously reported lower ventromedial hypothalamic nucleus (VMN) serotonergic activity in 11-wk genetically obese vs. lean Zucker rats. To determine whether the activity was secondary to metabolic alterations associated with this established obesity (e.g., significant hyperphagia and hyperinsulinemia), we examined monoaminergic activity in various brain nuclei of 12-day lean (Fa/Fa and Fa/fa) and obese (fa/fa) rats early in the development of obesity. Obese pups had greater percent carcass fat than heterozygotes, both of which were fatter than homozygous lean rats. Obese, but not heterozygous lean, pups were hyperinsulinemic vs. Fa/Fa pups. VMN 5- hydroxy-3-indoleacetic acid levels, an index of serotonin release, were lower in obese and heterozygous than in homozygous lean pups and were not correlated with plasma insulin levels. Although monoamine differences also occurred in several other nuclei, for the most part they appeared to be unrelated to the obese genotype. We conclude that blunted VMN serotonergic activity is not secondary to the obese rat's hyperinsulinemia and may play a significant role in the development of obesity.

Original languageEnglish (US)
Pages (from-to)R712-R719
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Issue number3 36-3
StatePublished - 1994
Externally publishedYes

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


  • development
  • hypothalamus
  • insulin
  • obesity
  • raphe nucleus


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