Regional studies of serotonin and dopamine metabolism and quantification of serotonin uptake sites in human cerebral cortex.

An increasing number of studies have indicated that neuronal metabolism of serotonin (5-HT) and other monoamines may be altered in patients with affective disorders and in completed suicides. However, studies have yielded discordant results. The purpose of this study was to determine the regional variation of 5-hydroxyindolacetic acid (5-HIAA), homovanillic acid (HVA), (5-HT) and 5-HT uptake sites within the human cerebral cortex. Our sample consisted of 19 patients who died suddenly and accidently. Cortical concentrations of 5-HIAA, HVA and 5-HT were measured in six regions using an HPLC. 5-HT uptake sites in cortex were examined using [3H]-Paroxetine. 5-HT values within each brain were fairly constant in cortical regions studied except for the posterior parietal areas. By contrast, 5-HIAA values showed a trend towards a rostro-caudal increase, with peak values seen at sections corresponding to the post-central gyrus and the occipital pole. Using the ratio of 5-HIAA/5-HT as a crude index of 5-HT turnover, there was a progressive rostro-caudal increase of values which achieved statistical significance: the posterior superior parietal area and the occipital pole displayed a greater ratio than the other four cortical regions. HVA values were highest in the pre-central region and decreased both rostrally and caudally. 5-HIAA and HVA values were correlated positively in 5 of 6 cortical areas, while 5-HIAA and 5-HT were correlated in areas 4 and 5. Results obtaining using [3H]-Paroxetine suggest that 5-HT uptake sites in the human cortex are distributed rather uniformally and are not correlated with 5-HT levels.