Hypothalamic GABA-ergic activity and T-cell proliferation in aged mammal: effect of dietary protein.

Short-term supplementation of low protein diet (LPD) or high protein diet (HPD) to the aged (18 months old) rats did not change the hypothalamic GABAergic activity and immune response. Long-term supplementation of LPD on the other hand, enhanced hypothalamic GABAergic activity with an immunopotentiation by increasing the T-cell proliferating activity and peripheral blood lymphocyte count in the same age group of rats. Unlike LPD, HPD under long-term supplementation to the aged rats reduced the hypothalamic GABAergic activity with immunosuppression. These results thus suggest that (i) hypothalamic GABAergic activity is a regulatory index of immune response in aged mammals and (ii) long-term consumption of protein-poor or protein-rich diet may be an exogenous modulator of neuroimmune regulation in relation to central GABAergic activity and immune response.