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Chemical Sensation Modulated by High Gravity Stress at Different Growth Stage in Rats.    M. Kimoto¹, S. Takase¹, K. Toda^1,2 and Y. Kumei.^{3  1}Physiological Laboratory, Japan Women's University, Tokyo, ²Integrative Sensory Physiology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, and ³Biochemistry, Graduate School of Tokyo Medical and Dental University, Tokyo, JAPAN.

   We previously reported that gravity stress modified nociceptive processing system in rats. This suggests that stressful stimulation by gravity change may modify various sensory systems closely related to emotion including taste sensation. In addition, the developing or growth stage is thought to be critical for inducing sensory modification by stress. Therefore, in the present study, we investigated effects of high gravity stimulation on chemical sensation depending on the growth stages of rats. Using male Wistar albino rats, gravity stimuli varied at 2.0–3.0G were applied by centrifugation for 10 min once daily at the growth stages of 1-15 postnatal days (STAGE I), 24 -68 days (STAGE II). As for chemical solutions, sucrose, saccharin, NaCl, caffeine, citric acid, ascorbic acid, sodium glutamate, quinine and capsaicin were used. Results: (1) STAGE I: 2.0 G application induced stress-resistance reaction for chemical sensory system. (2) STAGE II: 3.0 G application significantly modified the taste sensation of sweet and salt, and in addition, somatosensory irritable sensation induced by capsaicin. Data suggest that gravity stimulation is critical for modification of chemical sensation at the infant stage of rats.

Supported by a Grant-in-Aid for scientific research from the Ministry of Education, Science, Sports and Culture of Japan (No.18500630, No.18613011, 2006-2007).