AGE-ASSOCIATED ALTERATIONS IN SYMPATHETIC NEURAL INTERACTIONS WITH THE IMMUNE-SYSTEM

We have examined age-related alterations in sympathetic noradrenergic (NA) innervation in primary and secondary lymphoid organs from mouse a nd rat, As the thymus involuted with age, the density of NA innervatio n and norepinephrine (NE) concentration increased markedly, Total thym ic NE was not altered significantly with age, suggesting that NA inner vation is maintained as the thymus involutes, In the rat spleen, NA in nervation and NE concentration were diminished with age, Enhanced anti body responses and in vitro proliferation to a T-dependent protein ant igen were observed following selective destruction of NA nerve fibers with the neurotoxin 6-hydroxydopamine (6-OHDA), demonstrating that the diminished NA innervation in the aged spleen is capable of signaling the immune system. Plasticity of NA nerves in old rats was demonstrate d following lesioning with 6-OHDA and in intact rats treated with L-de prenyl, a monoamine oxidase B inhibitor, These age-related alterations in NA innervation of lymphoid organs occur concurrently with age-asso ciated changes in immune function, Understanding the functional relati onship between these two physiological systems in aging will contribut e to a greater understanding of sympathetic nervous system regulation of immune function. (C) 1997 Elsevier Science Ltd. All rights reserved .