Avoidance behavior and neural correlates of allergen exposure in a murine model of asthma.

Allergic asthma is characterized by intermittent airway obstruction, inflammation, airway hyperreactivity, and increased production of IgE. The pathophysiology of asthma is well understood but little is known about its influences on brain activity and behavior. We recently described the neural correlates of food allergy and its associated modulation of behavior using an experimental model that also generates a T helper type 2 (Th2)-skewed response, with high levels of IgE. Here we show that mice allergic to ovalbumin (OVA) have an increase in the activity of the paraventricular nucleus of the hypothalamus (PVN) and in the central nucleus of the amygdala (CeA) following a single nasal OVA challenge. Moreover, we adapted a classical passive avoidance test using an OVA aerosol as the aversive stimulus. We found that allergic mice avoid entering the dark compartment of the apparatus that had been previously associated with nebulization of the allergen, while their non-immunized controls still move into the dark side of the test box. Thus, allergic mice have increased activity in areas of the CNS commonly associated with emotionality-related behavioral responses, such as the avoidance of a context previously associated with an unpleasant or harmful situation. Moreover, our findings on the avoidance test illustrate that previous experience with an airborne allergen can modify behavior.