Neural correlates of IgE-mediated allergy.

Although many authors have considered a direct interaction between allergic reactions and behavioral changes, supporting evidence has been elusive. In this series of studies we show that after oral or nasal ovalbumin (OVA) challenge, allergic mice present increased Fos expression in the paraventricular nucleus of the hypothalamus (PVN) and in the central nucleus of the amygdala (CeA). Mice with food allergy display higher levels of anxiety and increased serum corticosterone levels, and allergy-activated neurons express corticotropin-releasing factor (CRF) in the PVN and CeA. OVA-allergic mice develop aversion to an antigen-containing solution, and also avoid a dark compartment previously associated with nebulized OVA. Results on brain Fos expression and behavioral data seem compatible with adaptive responses. Removal of IgE by either antibody depletion or the development of oral tolerance precluded all responses analyzed here. C-sensitive fiber destruction by neonatal capsaicin inhibited the activation in the PVN, but not in the CeA, and decreased the magnitude of food aversion. Cromolyn, a mast cell stabilizer, completely blocked Fos expression in the PVN and CeA, and precluded the development of aversion to the dark compartment associated with nebulized OVA. Employing mice that do not develop an important inflammatory infiltrate following nasal OVA challenge, we found that inflammatory cells are not required at the site of challenge in order to trigger neural or behavioral correlates of murine experimental asthma. Altogether, we have built a solid foundation for understanding neuroimmune interactions during allergic responses that may contribute to the comprehension of psychological disorders associated with allergy.