Late changes in cerebral monoamine metabolism following focal ventrolateral cerebrocortical lesions in rats.

Twelve weeks after focal ventrolateral cerebrocortical suction lesions (ca. 12 X 4 mm) were made in rats, concentrations of the monoamines norepinephrine (NE), dopamine (DA), and serotonin (5-HT) and their metabolites were measured in several cortical and subcortical brain regions using high performance liquid chromatography with electrochemical detection. Widespread changes in the concentrations of monoamines, their metabolites, and metabolite:monoamine ratios were found in the hemisphere ipsilateral to unilateral (right) lesions, and bilaterally in animals with bilateral lesions. NE was decreased in undamaged dorsolateral cortex and hippocampus, and tended to be increased in striatum and midbrain ipsilateral to lesions. DA was increased in the hypothalamus of bilaterally lesioned animals, and also tended to be increased in striatum and midbrain. The changes of greatest magnitude and anatomical extent were found in the serotonin system: 5-HT was generally increased, and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) and the 5-HIAA:5-HT ratio were decreased throughout the cerebral hemispheres ipsilateral to lesions. These widespread changes in cerebral 5-HT metabolism were qualitatively different and smaller than those previously found at 6 days after cortical lesions, and suggest a biphasic response of the ipsilateral 5-HT system to ventrolateral cortical injury.