Stress and chewing affect blood flow and oxygen levels in the rat brain.
OBJECTIVE
Mastication, including chewing, would be of great importance not only for food intake, but also for the mental, physical and physiological functioning of the body. Our study showed that mastication, especially chewing, suppresses the stress response and was regarded as a biological response to defend against various stresses. Although mastication altered brain function during stress, the underlying mechanisms have not been elucidated.


METHODS
The effects of chewing during restraint stress on blood flow and oxygen partial pressure (PO(2)) levels in the rat amygdala and hypothalamus were measured using laser Doppler flowmetry and O(2)-selective electrodes.


RESULTS
Amygdaloidal and hypothalamic blood flow were not affected by restraint stress, but PO(2) levels were significantly reduced by restraint stress for 180 min compared to unrestrained control rats. The decrease in amygdaloidal and hypothalamic PO(2) levels during restraint stress was reduced after chewing for 30 min.


CONCLUSIONS
These results suggested that it is possible to evaluate hypothalamic and amygdaloidal blood flow and PO(2) levels in rat brains during restraint stress. Restraint stress reduced cerebral PO(2) levels. In addition, chewing would lead to increased blood flow and to recover cerebral PO(2) levels.
Department of Craniofacial Growth and Development Dentistry, Division of Orthodontics, Kanagawa Dental College, 82 Inaoka-cho, Yokosuka, Kanagawa 238-8580, Japan.
Shinjiro
S
Miyake
Satoko
S
Wada-Takahashi
Hiroyuki
H
Honda
Shun-Suke
SS
Takahashi
Kenichi
K
Sasaguri
Sadao
S
Sato
Masaichi-Chang-Il
MC
Lee
D000679:Amygdala / Q000098:blood supply*; D000818:Animals; D006439:Hemodynamics / Q000502:physiology*; D007031:Hypothalamus / Q000098:blood supply*; D017078:Laser-Doppler Flowmetry; D008297:Male; D008409:Mastication / Q000502:physiology*; D010100:Oxygen / Q000097:blood*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012149:Restraint, Physical / Q000502:physiology; D013312:Stress, Physiological / Q000502:physiology*; D013315:Stress, Psychological / Q000097:blood* / Q000503:physiopathology
D010100:Oxygen