Correlation between food intake and cerebrospinal fluid interleukin 1 alpha in anorectic tumor-bearing rats

Anorexia is observed in 50% of cancer patients; however, the pathogenesis for cancer anorexia is unclear. We postulate that centrally acting cytokines play a role in the pathogenesis of cancer anorexia. To test our hypothesis we determined whether central interleukin 1 alpha (IL-1 alpha) was related to anorexia in tumor-bearing (TB) rats. Fischer 344 rats were inoculated with either 1 ml of 1 x 10(6) trypan blue viable methylcholanthrene-induced sarcoma cells (TB rats) or normal saline (non-tumor-bearing [NTB] rats). Rats were placed into individual metabolic cages equipped with an Automated Computerized Rat Eater Meter that continuously measured food intake. When TB rats became anorectic, TB and NTB rats were anesthetized and cerebrospinal fluid (CSF) was collected. IL-1 alpha was measured. Food intake in TB was 7.1 +/- 1.1 g, whereas that in NTB was 12 +/- 1.1 g (p < 0.05). Eight of the 13 TB rats had detectable concentrations of CSF IL-1 alpha; the mean CSF IL-1 alpha concentration for TB rats was 73.2 +/- 17.3 pg/ml. In contrast, none of the NTB rats (n = 11) had detectable concentrations of CSF IL-1 alpha. CSF IL-1 alpha concentrations correlated inversely with food intake. Data suggest a link between CSF IL-1 alpha and food intake in anorectic TB rats.