Alleviating effects of plant-derived fragrances on stress-induced hyperthermia in rats.

In the present study, the effects of exposure to plant-derived odors on the autonomic and behavioral responses to novel environment were examined in rats. Male rats (n=42) carrying a telemetry transmitter were individually housed, and on the test day each rat was transferred to a new cage containing bedding that had been sprayed immediately before testing with 200 microl of 0.03% dilution of either lavender essential oil, green leaf odor (a mixture of hexenol and hexenal), alpha-pinene, or solvent (triethyl citrate) as a control. Following the transfer to this novel environment, the body temperature of the rats increased by nearly 1 degrees C, showing a stress-induced hyperthermia. Stress-induced hyperthermia was attenuated by the green odor and the alpha-pinene, but not by the lavender or solvent. There was no clear effect of fragrances on heart rate or behavioral responses. These results suggest that plant-derived fragrances, such as green odor and alpha-pinene, have calming effects on autonomic stress response to novel environments.