A new approach to biochemical evaluation of brain dopamine metabolism

1. Dopaminergic neurotransmission in brain is receiving increased attention because of its known involvement in Parkinson's disease and new methods for the treatment of this disorder and because of hypotheses relating several psychiatric disorders to abnormalities in brain dopaminergic systems. 2. Chemical assessment of brain dopamine metabolism has been attempted by measuring levels of its major metabolite, homovanillic acid (HVA), in cerebrospinal fluid, plasma, or urine. Because HVA is derived in part from dopamine formed in noradrenergic neurons, plasma levels and urinary excretion rates of HVA do not adequately reflect solely metabolism of brain dopamine. 3. Using debrisoquin, the peripheral contributions of HVA to plasma or urinary HVA can be diminished, but the extent of residual HVA formation in noradrenergic neurons is unknown. By measuring the levels of methoxy-hydroxyphenylglycol (MHPG) in plasma or of urinary norepinephrine metabolites (total MHPG in monkeys; the sum of total MHPG and vanillyl mandelic acid (VMA) in humans) along with HVA, it is possible to estimate the degree of impairment by debrisoquin of HVA formation from noradrenergic neuronal dopamine and thereby better assess brain dopamine metabolism. 4. This method was applied to a monkey before and after destruction of the nigrostriatal pathway by the administration of MPTP.     

Effects of Acute Lorazepam Administration on Aminergic Activity in Normal Elderly Subjects: Relationship to Performance Effects and Apolipoprotein Genotype

The effects of acute lorazepam challenges on plasma (p) HVA, MHPG, and 5-HIAA, and their relationship to drug-induced cognitive and motor deficits and the apolipoprotein (APOE)-epsilon4 allele were examined. Eighteen healthy elderly (8 epsilon4 carriers) received placebo or acute oral lorazepam doses (0.5 mg or 1 mg) in random sequence, 1-week apart. Cognitive assessment and plasma levels of pHVA, pMHPG, and p5-HIAA were determined at baseline and at 1, 2.5, and 5 h postchallenge. There was no drug-to-placebo difference in monoamine levels and no consistent relationship between changes in monoamine levels and cognitive performance, regardless of epsilon4 status. However, the 1.0 mg dose increased p5-HIAA in epsilon4 carriers, whereas it caused a reduction in noncarriers. Higher baseline pMHPG and p5-HIAA levels were associated with better baseline memory. The epsilon4 allele may modulate the effect of lorazepam on p5-HIAA, but further studies are needed to confirm this finding and elucidate its possible significance.     

Postmortem Stability of Brain 3-Methoxy-4-Hydroxyphenylethyleneglycol and 3,4-Dihydroxyphenylethyleneglycol in the Rat and Mouse

Abstract: To assess the postmortem stability of brain 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) and 3,4-dihydroxyphenylethyleneglycol (DHPG) levels, groups of rats and mice were killed by cervical dislocation and left at either 21° or 4°C for intervals of up to 24 h until removal and freezing of whole brain. Whole brain free and total MHPG and DHPG levels were determined simultaneously by gas chromatography-mass fragmentography (GC-MF). By 2 h after death, statistically significant decrements occurred in rat brain free DHPG (20%), total MHPG (21%), and total DHPG (11%) at 4°C, but free MHPG increased significantly (50%) compared with controls. At 21°C, rat brain total MHPG increased compared with controls at 2 h (15%) but decreased at 4 h (15%) and 8 h (15%), whereas free MHPG levels were increased at these times. Although brain total and conjugated DHPG levels showed little change, free DHPG levels were reduced at all times. In mouse brain no significant changes occurred in free MHPG and DHPG by 24 h at 4°C. At 21°C, mouse brain DHPG levels decreased whereas MHPG concentrations increased over the 8-h period of study. These findings demonstrate the occurrence of significant postmortem time- and temperature-dependent changes in brain MHPG and DHPG concentrations and indicate caution in the interpretation of changes in these metabolites in studies employing human postmortem brain tissue.     

难治性抑郁症治疗前后血浆单胺类神经递质代谢产物的变化

目的：探讨难治性抑郁症患者抗抑郁剂治疗前后的单胺类神经递质代谢产物的改变。方法：随机入组30例难治性抑郁症患者,进行汉密尔顿抑郁量表（HAMD）的临床评定。用酶联免疫吸附方法对这30例患者进行5-HIAA,MHPG检测,并与随机选取的经汉密尔顿抑郁量表（HAMD）临床评定的30名普通抑郁症患者进行比较。综合治疗8周后对难治性抑郁症患者进行治疗前后对比。结果：难治性抑郁症组治疗前血浆5-HIAA,MHPG浓度低于普通对照组（p〈0.05）,经5-羟色胺重摄取抑制剂治疗的难治性抑郁症患者,5-HIAA和MHPG含量与治疗前比较均有所升高,差异有显著性（p〈0.05）;结论：难治性抑郁症患者存在中枢5-羟色胺和去甲肾上腺素功能低下;个体化合理使用SSRIs类药物辅以心理治疗能有效地提高难治性抑郁症患者的外周单胺类递质水平,减轻患者的抑郁程度。     

难治性抑郁症治疗前后血浆单胺类神经递质代谢产物的变化

目的:探讨难治性抑郁症患者抗抑郁剂治疗前后的单胺类神经递质代谢产物的改变。方法:随机入组30例难治性抑郁症患者,进行汉密尔顿抑郁量表(HAMD)的临床评定。用酶联免疫吸附方法对这30例患者进行5-HIAA,MHPG检测,并与随机选取的经汉密尔顿抑郁量表(HAMD)临床评定的30名普通抑郁症患者进行比较。综合治疗8周后对难治性抑郁症患者进行治疗前后对比。结果:难治性抑郁症组治疗前血浆5-HIAA,MHPG浓度低于普通对照组(p<0.05),经5-羟色胺重摄取抑制剂治疗的难治性抑郁症患者,5-HIAA和MHPG含量与治疗前比较均有所升高,差异有显著性(p<0.05);结论:难治性抑郁症患者存在中枢5-羟色胺和去甲肾上腺素功能低下;个体化合理使用SSRIs类药物辅以心理治疗能有效地提高难治性抑郁症患者的外周单胺类递质水平,减轻患者的抑郁程度。     

Fluoxetine increases extracellular levels of 3-methoxy-4-hydroxyphenylglycol in cultured COLO320 DM cells

Fluoxetine (Prozac) is a serotonin reuptake inhibitor. It increases extracellular levels of serotonin and is used in relieving the depressive symptoms of cancer patients. It has been reported that the drug may enhance the growth of certain cancer cells. This study investigates whether fluoxetine enhances the growth of a human colon cancer cell line (COLO320 DM) and if it affects the extracellular levels of serotonin or its metabolite, 5-hydroxyindole-3-acetic acid (5-HIAA) and other monoamines and metabolites at two cell densities. The extracellular levels of serotonin, 5-HIAA and other monoamines and metabolites were measured simultaneously by high performance liquid chromatography from cell-culture media after incubation of cells both with and without fluoxetine for 3 days. The viability of COLO320 DM cells was evaluated using 3-(4,5-cimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT). At low cell densities (1.25x10(5) cells ml-1), fluoxetine at 1-10 microM significantly increased the extracellular levels of serotonin (p<0.005), 5-HIAA (p<0.005), and 3-methoxy-4-hydroxyphenylglycol (MHPG; p<0.001) as compared to the controls. Fluoxetine at 10-100 microM significantly inhibited the growth of COLO320 DM (p<0.005). At high cell densities (2x10(6) cells ml-1), fluoxetine at 1-10 microM significantly increased the extracellular levels of MHPG (p<0.01), and at 10 microM it significantly increased the extracellular levels of 5-HIAA (p<0.05). Fluoxetine at 100 microM significantly inhibited the growth of the cells (p<0.0001). These results suggest that fluoxetine at 1 microM of effective concentration may increase the extracellular levels MHPG, in addition to serotonin and 5-HIAA levels, yet not inhibit the growth of COLO320 DM.     

Widespread alterations in central noradrenaline,dopamine, and serotonin systems in the Brattleboro rat not related to the local absence of vasopressin

A comprehensive study of monoamine transmitter and metabolite concentrations measured by HPLC was undertaken in female (vasopressin-deficient) Brattleboro rats as compared to Long Evans rats. Noradrenaline was significantly increased in 8 out of 13 dissected brain regions, whereas concentrations of the metabolite 3-methoxy-4-hydroxyphenylglycol were not altered. The increases were not restricted to areas which are normally innervated by vasopressin-containing neurons. Serotonin was increased in 6 and dopamine in 4 regions and this was accompanied in some areas by increases in the metabolites 5-hydroxyindolacetic acid and dihydroxyphenylacetic acid. Only in the striatum, cerebellum, and the medulla-pons no changes could be detected in any of the compounds of interest. These results show that the long term absence of vasopressin in Brattleboro rats appears to be associated with increases in monoamine transmitter contents and decreased metabolite/transmitter ratios. The regional distribution of these changes does not bear any relationship to the regional distribution of vasopressin cell bodies or nerve endings.