Attack-induced changes in response to decapitation of plasma catecholamines of victim mice

Male mice of 3 different strains (NIH, C57BR/cdJ and A/HeJ) were exposed individuality (victims) to attack by trained fighter Swiss Webster mice for 10 minutes daily for various numbers of days. Immediately after the last attack the victim mice were decapitated along with unattacked control mice of the appropriate strain, and plasma norepinephrine (NE) and epinephrine (E) were measured. The concentration of NE was significantly lower in decapitated C57BR/cdJ mice than in the other 2 strains. The concentrations of E and NE in the plasma of decapitated C57BR/cdJ and A/HeJ mice were significantly greater after 4 days of attacks, whereas in NIH mice plasma levels of only NE were greater and this occurred only after 14 days of attacks. After 7 days of exposure to attack, C57BR/cdJ and A/HeJ victim mice were permitted to rest for various periods of time. In C57BR/cdJ animals plasma E returned to almost normal levels after 2 days, and NE after 4 days, while in A/HeJ mice plasma E and NE returned to control levels already after 1 day of rest.