Inhibition of tumor growth by L-deprenyl involves neural-immune interactions in rats with spontaneously developing mammary tumors

L-deprenyl, a monoamine oxidase-B inhibitor; has been shown to reverse the age-related decline in sympathetic noradrenergic innervation and immune fun ction in old mts and enhance T cell and NK cell activity in tumor-bearing m ts. The objective of the present study was to examine whether deprenyl trea tment of old female rats with mammary tumors could augment sympathetic nerv ous system and immune responses to inhibit the tumor growth. Female Sprague -Dawley rats with spontaneous mammary tumors were administered 0, 2.5 mg, o r 5.0 mg/kg body weight (BW)/day deprenyl for i.p. 9 weeks. Tumor diameter, tumor number and body weight were measured throughout the treatment period . At the end of the treatment period, norepinephrine (NE) concentration, in terferon-gamma production (IFN-gamma), Con A-induced T lymphocyte prolifera tion, and percentage of T and B lymphocytes and natural killer cells were m easured in the spleen, and the concentrations of monoamines were measured i n the medial basal hypothalamus. Relative to saline-treated controls, treat ment with deprenyl reduced tumor growth, increased NE concentration, IFN-ga mma production and percentage of the CD8+ T lymphocytes in the spleen. In t he medial basal hypothalamus, deprenyl treatment increased die concentratio ns of catecholamines and indole-amine. These results suggest that the anti- tumor effects of deprenyl on spontaneous rat mammary armors may be achieved via neural-immune signaling in the spleen and medial basal hypothalamus.