Differential Early Time Course Activation of the Brainstem Catecholaminergic Groups in Response to Various Stresses

The effects of various stressors (restraint, ether, histamine and insulin-induced hypoglycemia stress) on the early time course activation of the different catecholaminergic (CA) cell groups A1/C1, A2/C2 and locus ceruleus (LC) from the brainstem were studied. The activity of the central noradrenergic neurons was assessed by measuring in tissue punches the 3,4-dihydroxyphenylacetic acid (DOPAC) level, a side metabolite of noradrenaline (NA) and adrenaline biosynthesis that is thought to reflect the activity of NA cells. Short 5 min restraint stress led to an immediate increase of DOPAC level in the three CA groups. In the A1/C1 and A2/C2 groups the maximal increase, respectively +75 and +50%, was already reached at the end of the application of the stress while for the LC the maximum (+84%) was obtained 15 min after the onset of the stress. Return to baseline level was achieved within 2 h. Continuous immobilization stress did not further alter the DOPAC concentration in the LC and the A1/C1 while a progressive increase up to 85% in the A2/C2 group was seen over 20 min. Following a 2-min exposure to ether, DOPAC was increased in all three structures within 5 min. At this time the maximum was already reached in the A1/C1 and LC, respectively +99 and +43%. After histamine or insulin injection DOPAC level increased in the A1/C1 and A2/C2 in the +25/+50% range but was not significantly affected in the LC. In all the stress situations studied the increase in DOPAC level, particularly in the A1/C1 group always preceded or was concomitant to the increase of plasma corticosterone.(ABSTRACT TRUNCATED AT 250 WORDS)