Vh. Routh et al., SEROTONERGIC ACTIVITY IS DEPRESSED IN THE VENTROMEDIAL HYPOTHALAMIC NUCLEUS OF 12-DAY-OLD OBESE ZUCKER RATS, The American journal of physiology, 267(3), 1994, pp. 180000712-180000719
We previously reported lower ventromedial hypothalamic nucleus (VMN) s
erotonergic activity in ll-wk genetically obese vs. lean Zucker rats.
To determine whether the activity was secondary to metabolic alteratio
ns associated with this established obesity (e.g., significant hyperph
agia and hyperinsulinemia), we examined monoaminergic activity in vari
ous brain nuclei of 12-day lean (Fa/Fa and Fa/fa) and obese (falfa) ra
ts early in the development of obesity. Obese pups had greater percent
carcass fat than heterozygotes, both of which were fatter than homozy
gous lean rats. Obese, but not heterozygous lean, pups were hyperinsul
inemic vs. Fa/Fa pups. VMN 5-hydroxy-3-indoleacetic acid levels, an in
dex of serotonin release, were lower in obese and heterozygous than in
homozygous lean pups and were not correlated with plasma insulin leve
ls. Although monoamine differences also occurred in several other nucl
ei, for the most part they appeared to be unrelated to the obese genot
ype. We conclude that blunted VMN serotonergic activity is not seconda
ry to the obese rat's hyperinsulinemia and may play a significant role
in the development of obesity.