Effects of L-deprenyl treatment on noradrenergic innervation and immune reactivity in lymphoid organs of young F344 rats

Sympathetic noradrenergic (NA) neuronal activities in the thymus, spleen an d mesenteric lymph nodes (MLN) and immune responses in the spleen were exam ined in young male F344 rats treated daily with 0, 0.25 mg, or 2.5 mg/kg bo dy weight of L-deprenyl, an irreversible monoamine oxidase-B (MAO-B) inhibi tor. Rats were treated daily for 1, 15, or 30 days, and sacrificed 7 days a fter the last deprenyl treatment. Deprenyl treatment increased norepinephri ne (NE) content in the spleen without modifying the pattern and density of NA innervation in the splenic white pulp. The concentration of NE was unalt ered in the thymus, but it was increased in the MLN of deprenyl-treated rat s. One day of treatment with deprenyl decreased splenic NK cell activity wh ile 15 days of deprenyl treatment enhanced splenic NK cell activity. Depren yl elevated Con A-induced T lymphocyte proliferation following 30 days of t reatment, but did not alter spleen cell Con A-induced IL-2 production or th e percentage of CD5 + T cells in the spleen. A moderate decrease in the per centage of sIgM + B cells was observed in the spleens of 15- and 30-day dep renyl-treated rats. These results suggest that deprenyl has sympathomimetic action on sympathetic NA nerve fibers in the spleen; the enhancement of NA neuronal activity may contribute to the modulation of immune responses in the spleen. (C) 1999 Elsevier Science B.V. All rights reserved.