Because adrenalectomy tends to normalize many metabolic abnormalities
of obese Zucker rats, we hypothesized that it would also normalize the
depressed serotonergic turnover in their ventromedial nucleus (VMN).
Lean (Fa/Fa) and obese (fa/fa) male Zucker rats were adrenalectomized
or sham operated when 5 wks old and sacrificed at 11 wks. Their brains
were frozen, and 13 areas were dissected for HPLC-EC analysis of mono
amines and metabolites. Consistent with previous studies, VMN serotoni
n turnover (indexed by 5-HIAA/5-HT) was lower in obese than lean sham-
operated rats. Monoamine and metabolite concentrations were altered in
several other brain areas as well. Adrenalectomy reduced percent body
fat and elevated VMN serotonergic turnover more in obese than in lean
rats. It also stimulated serotonergic turnover in almost every brain
area examined. We conclude that in obese Zucker rats: monoaminergic ac
tivity is altered in several brain areas involved in regulating energy
balance; adrenalectomy normalizes the reduced VMN serotonergic turnov
er seen in the obese rats; and adrenalectomy results in a generalized
increase in central serotonergic turnover. These data are consistent w
ith serotonin's role in inhibiting food intake and enhancing sympathet
ic stimulation of energy metabolism.