GENDER DIFFERENCES IN SYMPATHOADRENAL ACTIVITY IN RATS AT REST AND INRESPONSE TO FOOTSHOCK STRESS

A comparison was made of the dynamics of sympathoadrenal activity in 1 1 age-matched male and female rats, under basal conditions and after e xposure to footshock. Rats were prepared with indwelling catheters in the tail artery 24 h before the experiment. Measurements were made of plasma corticosterone (COR), norepinephrine (NE), epinephrine (EPI), d ihydroxyphenylalanine (DOPA), dihydroxyphenylglycol (DHPG) and dihydro xyphenylacetic acid (DOPAC) under resting conditions, after transfer t o the shock box (novelty) and at various times after footshock. Under basal conditions, males have significantly higher blood pressure and p lasma DHPG/NE ratios but lower plasma levels of COR, NE and DOPAC than females. Three min after exposure to the shock chamber (novelty stres s) there were significant increases in COR, EPI, NE and DHPG in both s exes, while DOPA increased only in females and DOPAC remained unchange d in both sexes. Footshock produced a further increase in EPI, NE and DOPAC within 2 min, which lasted about 15 min. There were significant sex differences in the extent and duration of the response of COR, EPI and DHPG. The data show that the female sympathoadrenal system is mor e reactive than that of the male to the stresses of a never environmen t and footshock. The smaller DHPG/NE ratios in females at rest and aft er stress suggest that neuronal uptake of NE is lower in females than in males. The finding that stress produces larger increments of plasma DOPA and DOPAC in female rats indicates that tyrosine hydroxylase in the sympathetic nerve terminals and adrenal medulla may also be higher than in males. (C) 1998 ISDN. Published by Elsevier Science Ltd.