The formation of deaminated metabolites of dopamine in the locus coeruleus depends upon noradrenergic neuronal activity.

The effect of manipulations of noradrenergic neuronal activity on the levels of the deaminated metabolites of dopamine in the locus coeruleus has been investigated in the rat. Antidromic stimulation of the locus coeruleus increased the levels of 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 3-methoxy-4-hydroxyphenylethyleneglycol (MOPEG) in this area. Conversely, local infusion of tetrodotoxin into the locus coeruleus reduced the levels of these metabolites in this region. After systemic injection, idazoxan increased whereas clonidine diminished DOPAC, HVA and MOPEG levels in the locus coeruleus either in normal animals or in animals bearing a lesion of A9 and A10 dopaminergic cells. These results suggest that the formation of dopamine deaminated metabolites in noradrenergic cell bodies is dependent upon, and may serve as an index of, central noradrenergic neuronal activity.