Background: Tumor growth in animals and humans is associated with the onset
of anorexia and reduced food intake. We previously demonstrated that the v
entromedial nucleus of hypothalamus (VMN) plays a contributory role in medi
ating cancer anorexia, Because serotonin and interleukin-1 (IL-1) are putat
ive mediators of cancer anorexia. we hypothesized that their influence on f
ood intake during tumor growth might occur via their action within the VMN.
Methods: To test this hypothesis, 12 Fischer rats injected subcutaneously w
ith 10(6) viable MCA sarcoma cells (TB rats) and their nontumor-bearing con
trols (NTB, n=13) were studied. When anorexia developed, TB and NTB rats re
ceived bilateral intra-VMN microinjections of the serotonin antagonist mian
serin (200 nmol) or the IL-1 receptor antagonist (IL-1ra, 25 ng), Food inta
ke and its determinants of meal number and size were continuously recorded
via a computerized device.
Results: In NTB rats, intra-VMN mianserin did not affect food intake, where
as after IL-1ra or vehicle a momentary decrease in food intake due to a pre
dominant reduction of meal size occurred. In TB rats, intra-VMN mianserin o
r IL-1ra selectively increased meal number, leading to improved food intake
.
Conclusions: Data suggest that intra-VMN serotonin and IL-1 are involved in
influencing cancer related anorexia.