Alarm pheromone enhances stress-induced hyperthermia in rats

Behavioral and physiological effects of alarm pheromones emanating from str essed conspecific animals were investigated. Experimentally naive male Wist ar rats were exposed to the test chambers containing alarm pheromones, whic h had been released by other rats receiving foot shocks in the same chamber beforehand. Along with behavioral analysis, the heart rate (HR) and core b ody temperature (cBT) were measured simultaneously using a biotelemetory sy stem. Exposure to the alarm pheromones increased freezing, sniffing and wal king and decreased resting as compared with rats exposed to control odors. In addition, these pheromone-exposed animals showed consistent increases in body temperature, i.e., stress-induced hyperthermia. After exposure to the alarm substances, immunoreactivity to nuclear Fos protein in the mitral ee l layer in the accessory olfactory bulb (AOB) also increased compared with the reaction to control odors. These results suggest that alarm pheromones enhances stress responses of conspecific animals both behaviorally and phys iologically, and that these effects are mediated via activation of the AOB. (C) 2001 Elsevier Science Inc. All rights reserved.