Delay of cancer anorexia following intraventricular injection of para-chlorophenylalanine.

Serotonergic mediation of cancer anorexia was investigated in immature female rats following the intraventricular injection of para-chlorophenylalanine (PCPA) or normal saline. Significant anorexia developed 6 days after the induction (IM) of Walker 256 carcinosarcomas in saline-treated rats. Although tumor-bearing rats treated with PCPA ate less than PCPA-injected controls by day 7, their feeding response was significantly greater than that of saline-treated tumor-bearing rats on days 5, 6 and 7. The PCPA treatment had no significant effect on food intake in nontumor-bearing rats. Biochemical analysis revealed significant elevations in plasma free tryptophan, brain tryptophan and brain 5-hydroxyindoleacetic acid in saline-treated tumor-bearing rats. Brain serotonin, 5-hydroxyindoleacetic acid and norepinephrine levels were decreased in PCPA-treated rats. Although these data may provide some support for a serotonergic mediation of cancer anorexia, additional mechanisms are clearly indicated.