Masakatsu Takahashi (1) and Hiroshi Kaneto (2)
(1) Department of Pharmacoinformatics, School of Pharmaceutical Sciences,
Nagasaki University,(2) Emeritus Professor, Nagasaki University, 1-14, Bunkyo-machi,
Nagasaki 852-8521, Japan
Abstract: The antinociceptive effect induced by exposure to socio-psychological
(PSY) stress using a communication box was assessed by the formalin test
in mice, compared with those by exposure to footshock (FS) stress and forced
swimming (SW) stress. After the termination of stress exposure, whereas
exposure to FS- and SW-stress resulted in the attenuation of the formalin-induced
biphasic pain response over 15 min, no appreciable antinociceptive effect
was found in the case of PSY stress. When exposure to PSY stress was started
during the period of early or late phase of pain after the formalin injection,
the antinociceptive effect was maintained for 5 - 15 min; however, further
exposure to PSY stress was not effective for producing antinociception.
In the tail-pinch test, likewise, exposure to PSY stress longer than 5 min
rather decreased the intensity of antinociception. We conclude that PSY
stress in this tonic pain paradigm produces antinociception, but further
continuous exposure to the emotional stress caused mice to become recuperative
even in such a fear-inducing situation.
Keywords: Stress-induced analgesia (SIA), Socio-psychological stress,
Formalin test, Emotional stress, Communication box