Alterations of mouse adrenal medullary catecholamines and enzymes in response to attack: effect of pre- and post-treatment with phenobarbital.

Group-housed male C57BR/cdJ mice (victims) were exposed to attack for 10 min daily for up to 14 days by male Swiss-Webster mice, made aggressive by prolonged isolation. Their adrenal glands were analyzed for tyrosine hydroxylase (TH) and phenylethanolamine-N-methyltransferase (PNMT) activities and for norepinephrine (NE) and epinephrine (EPI) concentrations. TH was increased to 41 per cent above control after two exposures and remained elevated through 14 exposures to attack. PNMT was increased to 29 per cent above control after 2 days and increased further to 50 per cent above control after 14 days of attack. Both NE and EPI increased to 88 per cent and 51 per cent above control, respectively, after 7 days. In victim mice recuperating after 1 week of daily stress, EPI levels and PNMT activities were back to normal after 4 days whereas NE levels and TH activities returned to normal only after 1 week. Phenobarbital (40 mg/kg, i.m.) was effective in preventing the biochemical changes when given 2 h prior to each daily attack but was ineffective when given immediately after each daily stress.

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.

Effects of vinblastine on catecholamine-biosynthetic enzymes in heart, sympathetic ganglion and adrenal glands of rats.

1. The effect of vinblastine on the activities of dopamine-beta-hydroxylase (DBH) in heart, superior cervical ganglion and adrenal glands of rats and tyrosine hydroxylase (TH) and phenylethanolamine-N-methyl transferase (PNMT) in adrenal glands was examined.2. In the superior cervical ganglion and heart, DBH activity decreased within hours, reached a minimum in 3 to 5 days and slowly returned towards normal over the next 2 weeks.3. There was an increase in the activities of TH, DBH and PNMT in adrenal glands which was prevented by adrenal denervation.4. When the same total dose of vinblastine was administered subdivided over a period of 5 days, enzyme activities in heart, superior cervical ganglion or adrenal glands remained unchanged.