Different sensitivity to chronic stress induced cognitive deficit and immune alteration in BALB/c and C57BL/6 inbred mice. Involvement of hippocampal NO production and Th1/Th2 balance.

MARÍA LAURA PALUMBO; ANA MARÍA GENARO

Psyschology of Stress: New Research

Nova Science Publisher

Lugar: Nueva York; Año: 2013; p. 127 - 152

Stress is defined as any situation capable of perturbing the physiological or psychological homeostasis. While response to stress is a necessary survival mechanism, prolonged stress can have several repercussions affecting behavioral, endocrine and immunological parameters. Two genetically different inbred murine strains C57BL/6 and BALB/c, show distinct behavioral and immunological responses. In this chapter we show a comparative study on the effect of chronic mild stress upon learning and memory and immunity in BALB/c and C57BL/6 mice. Stressed BALB/c showed a poor learning performance related to structural and neurochemical changes observed in the hippocampus, such us a decrease of neurogenesis, a decrease of neural nitric oxide synthase (nNOS) activity and an increase in reactive oxygen species (ROS) levels. These alterations were not found in C57BL/6 mice subjected to CMS. In vivo administration of a nNOS inhibitor induced behavioral alterations in both strains. Moreover, in vitro treatment with a nNOS inhibitor induced an increase in ROS levels. Respect to immune response, CMS BALB/c mice showed a decrease in the T-lymphocyte and an increase of B-lymphocyte mitogen-stimulated proliferation, and an imbalance towards Th2 cytokines. In addition, CMS BALB/c mice had a poor antibody production after in vivo immunization with a T-cell depending antigen. On the contrary, CMS C57BL/6 animals showed an increase in the reactivity of T-lymphocytes without changes in the B-lymphocytes reactivity, no changes in humoral response after immunization and an imbalance towards Th1 cytokines. Concerning to the participation of the classically stress-associated hormones (catecholamines and corticosterone) in the above mentioned findings, the results indicate that there was not a temporal coincidence between corticosterone and catecholamines increase and behavioral and immune alterations. Taking into account, our results suggest a different vulnerability to cognitive deficit and immune alterations after chronic stress exposure in BALB/c and C57BL/6 mice. These different responses could be related to a differential regulation of hippocampal NO production and peripheral Th1/Th2 cytokine balance. In addition, the relationship between these effects is also analyzed.