Monoamines and their metabolites in somatosensory, visual, and cingulate cortices of adult rat: differences in content and lack of sidedness.

Small areas of somatosensory, visual and cingulate cortex were microdissected and assayed for their monoamine content by high-performance liquid chromatography with electrochemical detection. No differences were found between the right and the left hemisphere for any area nor for any of the monoamines. The values averaged from left and right hemispheres for the sensory areas were significantly different from the cingulate in the content of norepinephrine, 4-hydroxy-3-methoxyphenylglycol, dopamine, 3,4-dihydroxyphenylacetic acid, homovanillic acid, 5-hydroxy-1-tryptophan, serotonin and 5-hydroxyindole-3-acetic acid. The two sensory cortices differed in their levels of norepinephrine, dopamine, 3-4-dihydroxyphenylacetic acid and homovanillic acid. In the latter comparison, the measured amounts were higher in somatosensory than in visual cortex. This biochemical heterogeneity in monoamine distribution may reflect specific innervation patterns for these compounds in these discrete cortical areas and allows differences in content to be related to functional specializations of the cerebral cortex.