Increased turnover of norepinephrine in the rat cerebral cortex during stress: Role of the locus coeruleus

Abstract

The effect of “stress” (electrical foot shocks) on the turnover of norepinephrine in the cerebral cortex (including hippocampus) was studied in rats with an acute unilateral lesion in the area of the locus coeruleus. The noradrenergic nerve terminals in the rat cerebral cortex are mainly supplied by norepinephrine-containing neurones originating in the locus coeruleus. Stress induces an increase of the rate of disappearance of norepinephrine after inhibition of catecholamine synthesis (with α-methyl-( p-tyrosine) and an increased formation of 3-methoxy-4-hydroxyphenylglycol sulphate (a major metabolite of norepinephrine in the brain) in the cerebral cortex; these changes were blocked in the ipsilateral cortex of rats with unilateral lesions in the locus coeruleus. These results suggest that the locus coeruleus plays an important role in mediating the effect of stress on the metabolism of norepinephrine in the cerebral cortex.