Subthalamic Nucleus Deep Brain Stimulation Modulate Catecholamine Levels with Significant Relations to Clinical Outcome after Surgery in Patients with Parkinson's Disease

Aims

Although subthalamic nucleus deep brain stimulation (STN-DBS) is effective in patients with advanced Parkinson’s disease (PD), its physiological mechanisms remain unclear. Because STN-DBS is effective in patients with PD whose motor symptoms are dramatically alleviated by L-3,4-dihydroxyphenylalanine (L-DOPA) treatment, the higher preoperative catecholamine levels might be related to the better clinical outcome after surgery. We aimed to examine the correlation between the preoperative catecholamine levels and postoperative clinical outcome after subthalamic nucleus deep brain stimulation. The effectiveness of STN-DBS in the patient who responded well to dopaminergic medication suggest the causal link between the dopaminergic system and STN-DBS. We also examined how catecholamine levels were modulated after subthalamic stimulation.

Methods

In total 25 patients with PD were enrolled (Mean age 66.2 ± 6.7 years, mean disease duration 11.6 ± 3.7 years). Mean levodopa equivalent doses were 1032 ± 34.6 mg before surgery. Cerebrospinal fluid and plasma catecholamine levels were measured an hour after oral administration of antiparkinsonian drugs before surgery. The mean Unified Parkinson’s Disease Rating Scale scores (UPDRS) and the Parkinson’s disease Questionnaire-39 (PDQ-39) were obtained before and after surgery. Of the 25 patients, postoperative cerebrospinal fluid and plasma were collected an hour after oral administration of antiparkinsonian drugs during on stimulation at follow up in 11 patients.

Results

Mean levodopa equivalent doses significantly decreased after surgery with improvement in motor functions and quality of life. The preoperative catecholamine levels had basically negative correlations with postoperative motor scores and quality of life, suggesting that higher preoperative catecholamine levels were related to better outcome after STN-DBS. The preoperative plasma levels of L-DOPA had significantly negative correlations with postoperative UPDRS- III score in off phase three months after STN-DBS. The preoperative cerebrospinal fluid (CSF) 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxytryptamine (5-HT) levels had significantly negative correlations with postoperative UPDRS- III score in off phase one year after STN-DBS and the preoperative CSF homovanilic acid (HVA) levels had significant negative correlations with postoperative UPDRS- III score in on phase three months after STN-DBS. In PDQ-39 SI (summary index), preoperative plasma dopamine (DA) level had significantly negative correlations with postoperative PDQ-39 SI one year after STN-DBS suggesting that higher preoperative plasma DA level resulted in better quality of life (QOL) one year after STN-DBS. The stepwise multiple linear regression study revealed that higher preoperative plasma HVA levels had negative influence on the postoperative motor symptoms (i.e., increase in the score of UPDRS), whereas higher preoperative CSF L-DOPA levels had positive influence on the postoperative motor symptoms and QOL (decrease in the score of UPDRS and PDQ-39 SI) The catecholamine levels were not significantly reduced postoperatively in 11 patients despite the significant reduction in levodopa equivalent doses. Unexpectedly, CSF HVA levels significantly increased from 0.00089±0.0003 ng/μl to 0.002±0.0008 ng/μl after STN-DBS.

Conclusion

The preoperative catecholamine levels might affect the postoperative motor symptoms and quality of life. The catecholamine levels were not significantly reduced postoperatively despite the significant reduction in levodopa equivalent doses.

Nonuniform cardiac denervation observed by 11C-meta-hydroxyephedrine PET in 6-OHDA-treated monkeys

Parkinson's disease presents nonmotor complications such as autonomic dysfunction that do not respond to traditional anti-parkinsonian therapies. The lack of established preclinical monkey models of Parkinson's disease with cardiac dysfunction hampers development and testing of new treatments to alleviate or prevent this feature. This study aimed to assess the feasibility of developing a model of cardiac dysautonomia in nonhuman primates and preclinical evaluations tools. Five rhesus monkeys received intravenous injections of 6-hydroxydopamine (total dose: 50 mg/kg). The animals were evaluated before and after with a battery of tests, including positron emission tomography with the norepinephrine analog (11)C-meta-hydroxyephedrine. Imaging 1 week after neurotoxin treatment revealed nearly complete loss of specific radioligand uptake. Partial progressive recovery of cardiac uptake found between 1 and 10 weeks remained stable between 10 and 14 weeks. In all five animals, examination of the pattern of uptake (using Logan plot analysis to create distribution volume maps) revealed a persistent region-specific significant loss in the inferior wall of the left ventricle at 10 (P<0.001) and 14 weeks (P<0.01) relative to the anterior wall. Blood levels of dopamine, norepinephrine (P<0.05), epinephrine, and 3,4-dihydroxyphenylacetic acid (P<0.01) were notably decreased after 6-hydroxydopamine at all time points. These results demonstrate that systemic injection of 6-hydroxydopamine in nonhuman primates creates a nonuniform but reproducible pattern of cardiac denervation as well as a persistent loss of circulating catecholamines, supporting the use of this method to further develop a monkey model of cardiac dysautonomia.

Developing brain as an endocrine organ: secretion of dopamine

This study was aimed to test our hypothesis that the developing brain operates as an endocrine organ before the establishment of the blood-brain barrier (BBB), in rats up to the first postnatal week. Dopamine (DA) was selected as a marker of the brain endocrine activity. The hypothesis was supported by the observations in rats of: (i) the physiological concentration of DA in peripheral blood of fetuses and neonates, before the BBB establishment, and its drop by prepubertal period, after the BBB development; (ii) a drop of the DA concentration in the brain for 54% and in blood for 74% on the 3rd postnatal day after the intraventricular administration of 50 μg of α-methyl-p-tyrosine, an inhibitor of DA synthesis, with no changes in the DA metabolism in peripheral DA-producing organs. Thus, the developing brain is a principal source of circulating DA which is capable of providing an endocrine regulation of peripheral organs and the brain.

Increased blood oxidative stress in amphetamine users

Amphetamine derivatives have been shown to be a potential brain neurotoxin based on the production of free radicals that occurs after administration. The purpose of this study was to examine the lipid peroxidation and antioxidant enzymes in the blood of amphetamine users. The plasma lipid peroxidation was determined and reported as thiobarbituric acid reactive substance and was significantly increased (+21%), whereas the activities of the erythrocyte antioxidant enzymes glutathione peroxidase, catalase, and superoxide dismutase were significantly decreased (-32%, -14% and -31%, respectively) in amphetamine users. These results implicated the potential role of oxidative stress in amphetamine-induced neurotoxicity.

Plasma catechols in familial dysautonomia: a long-term follow-up study

This study tested whether familial dysautonomia (FD) involves progressive loss of noradrenergic nerves. Plasma levels of catechols, including dihydroxyphenylglycol (DHPG), norepinephrine (NE), dopamine (DA), and DOPA, were measured in 7 adult patients with FD and 50 healthy control subjects. FD patients were re-tested after a mean follow-up period of 13 years. Compared to controls, FD patients had low plasma levels of DHPG (P < 0.001), high DOPA and DA levels (P = 0.01, P = 0.0002), and high NE:DHPG (P < 0.0001), DA:NE (P = 0.0003), and DOPA:DHPG (P < 0.0001) ratios. At follow-up there were no changes in plasma levels of individual catechols; however, there were further increases in DOPA:DHPG ratios (mean 24 +/- 7%, P = 0.01). In FD, plasma catechol profiles are sufficiently stable, at least over a decade, to be used as a biomarker of disease involvement. An increasing DOPA:DHPG ratio suggests slight but consistent, progressive loss of noradrenergic neurons.

Neonatal diagnosis and treatment of Menkes disease

BACKGROUND

Menkes disease is a fatal neurodegenerative disorder of infancy caused by diverse mutations in a copper-transport gene, ATP7A. Early treatment with copper injections may prevent death and illness, but presymptomatic detection is hindered by the inadequate sensitivity and specificity of diagnostic tests. Exploiting the deficiency of a copper enzyme, dopamine-beta-hydroxylase, we prospectively evaluated the diagnostic usefulness of plasma neurochemical levels, assessed the clinical effect of early detection, and investigated the molecular bases for treatment outcomes.

METHODS

Between May 1997 and July 2005, we measured plasma dopamine, norepinephrine, dihydroxyphenylacetic acid, and dihydroxyphenylglycol in 81 infants at risk. In 12 newborns who met the eligibility criteria and began copper-replacement therapy within 22 days after birth, we tracked survival and neurodevelopment longitudinally for 1.5 to 8 years. We characterized ATP7A mutations using yeast complementation, reverse-transcriptase-polymerase-chain-reaction analysis, and immunohistochemical analysis.

RESULTS

Of 81 infants at risk, 46 had abnormal neurochemical findings indicating low dopamine-beta-hydroxylase activity. On the basis of longitudinal follow-up, patients were classified as affected or unaffected by Menkes disease, and the neurochemical profiles were shown to have high sensitivity and specificity for detecting disease. Among 12 newborns with positive screening tests who were treated early with copper, survival at a median follow-up of 4.6 years was 92%, as compared with 13% at a median follow-up of 1.8 years for a historical control group of 15 late-diagnosis and late-treatment patients. Two of the 12 patients had normal neurodevelopment and brain myelination; 1 of these patients had a mutation that complemented a Saccharomyces cerevisiae copper-transport mutation, indicating partial ATPase activity, and the other had a mutation that allowed some correct ATP7A splicing.

CONCLUSIONS

Neonatal diagnosis of Menkes disease by plasma neurochemical measurements and early treatment with copper may improve clinical outcomes. Affected newborns who have mutations that do not completely abrogate ATP7A function may be especially responsive to early copper treatment. (ClinicalTrials.gov number, NCT00001262.)

Recovery of brain dopamine metabolism by branched-chain amino acids in rats with acute hepatic failure

A decrease in the serum ratio of branched-chain amino acids (BCAAs) to aromatic amino acids (Fischer ratio) reflects the severity of hepatic encephalopathy, and clinical improvement by dietary augmentation with BCAAs has been demonstrated. As behavioral alteration results from changes in central neurotransmission, we investigated the role of BCAA administration on changes in the levels of central neurotransmitters in acute liver injury. Male Wistar rats were subjected to liver ischemia by occluding the left portal vein and hepatic artery for 90 minutes. A 4% BCAA solution containing valine, leucine, and isoleucine was intraperitoneally administered 3 times (8 mL/kg, each) at 1 hour, 6 hours, and 24 hours after vascular reperfusion, and changes in the extracellular concentrations of neurotransmitter amino acids, monoamines, and their metabolites were evaluated in the striatum by a microdialysis procedure. Although the extracellular concentration of dopamine was affected by neither liver ischemia nor BCAA injections, the level of 3,4-dihydroxyphenylacetic acid, a metabolite of dopamine, decreased to 34% in the ischemic group 24 hours after reperfusion. The 3,4-dihydroxyphenylacetic acid level was normalized by treatments with BCAAs. The improvement of deranged cerebral dopaminergic activity may be a contributing factor in the improvement of hepatic encephalopathy by BCAAs.

[Effect of dimethoate on serum monoamines neurotransmitters in rats]

OBJECTIVE

To study the effect of dimethoate on the monoamine Neurotransmitters, including norepinephrine (NE), epinephrine (E), serotonin (5-HT), dopamine (DA) and its metabolite (3, 4-hydroxyphenylacetic acid, DOPAC) in the serum of rats and furthermore to explore the non-cholinergic mechanism of organophosphate induced toxicity.

METHODS

Groups of rats were treated with saline and 38.9, 83.7 and 180 mg/kg dimethoate respectively and were decapitated at the different time course from 0.5 to 24 hours after the administration. The monoamines neurotransmitters were determined by the reverse-phase high-performance liquid chromatography with the electrochemical detection.

RESULTS

The serum concentrations of DA (8.42% - 248.42% of the control), DOPAC (17.22% - 68.21% of the control) increased, according with the DM dosage and the exposure time, while the levels of NE (9.65% - 38.26% of the control) and E (11.00% - 32.62% of the control) contents decreased at the same time.

CONCLUSION

These findings indicate that dimethoate induced toxic effects can alter the monoamine levels at the different dosage and the time exposure in the serum of rats. It suggests that some non-cholinergic mechanisms may be involved in the dimethoate intoxication.

Modified high-performance liquid chromatography with electrochemical detection method for plasma measurement of levodopa, 3-O-methyldopa, dopamine, carbidopa and 3,4-dihydroxyphenyl acetic acid

Plasma measurements of levodopa and its major metabolites including dopamine and 3-O-methyldopa have been limited by cumbersome methods and poor sensitivity within relatively narrow ranges of plasma levels. We now report a modification of an HPLC method that permits concomitant measurements of a wide range of concentrations of levodopa, dopamine (DA), carbidopa, 3-O-methyldopa (3-OMD) and 3,4-dihydroxyphenyl acetic acid (DOPAC) from one HPLC injection. The recoveries ranged from 77 to 107% with an intra-day precision around 5% (CV) and inter-day CV's about 10-20%. This validated method will simplify pharmacokinetic studies of levodopa and its metabolites for mechanistic studies or therapeutic clinical monitoring which play a crucial role in development of strategies to prolong motor benefits from individual doses and reduce involuntary movements called dykinesias.

Physiological and behavioral responses to interleukin-1beta and LPS in vagotomized mice

It is well established that peripheral administration of interleukin-1 (IL-1) and lipopolysaccharide (LPS) can activate the hypothalamo-pituitary-adrenocortical (HPA) axis, alter brain catecholamine and indoleamine metabolism, and affect behavior. However, the mechanisms of these effects are not fully understood. Stimulation of afferents of the vagus nerve has been implicated in the induction of Fos in the brain, changes in body temperature, brain norepinephrine, and some behavioral responses. In the present study, the IL-1beta- and LPS-induced changes in certain behaviors, HPA axis activation, and catecholamine and indoleamine metabolism were studied in mice following subdiaphragmatic vagotomy. IL-1beta and LPS induced the expected decreases in sweetened milk, food intake, and locomotor activity, and the responses to IL-1beta, but not LPS, were slightly attenuated in vagotomized mice. Subdiaphragmatic vagotomy also attenuated the IL-1beta- and LPS-induced increases in plasma ACTH and corticosterone, but the attenuations of the responses to IL-1beta were only marginally significant. There were also slight reductions in the responses in catecholamine and serotonin metabolism, and the increases in brain tryptophan in several brain regions. These results indicate that the vagus nerve is not the major pathway by which abdominal IL-1beta and LPS effect behavioral, HPA and brain catecholamine and indoleamine responses in the mouse. These results resemble those we observed in subdiaphragmatically vagotomized rats, but in that species the subdiaphragmatic vagotomy markedly attenuated the ACTH and corticosterone responses, and prevented the hypothalamic noradrenergic activation, as well as the fever. Overall the results indicate that the various responses to peripheral IL-1 and LPS involve multiple mechanisms including vagal afferents, and that there are species differences in the relative importance of the various mechanisms.

Effects of short-term early gestational exposure to endophyte-infected tall fescue diets on plasma 3,4-dihydroxyphenyl acetic acid and fetal development in mares

Consumption of wild-type (toxic) endophyte-infected tall fescue (E+) by horses during late gestation is known to adversely affect pregnancy outcome; however, little is known of the potential disruptive consequences of E+ consumption by mares during the critical phases of placentation and fetal development in early pregnancy. The objective of this study was to evaluate the detrimental effects of feeding E+ to mares during early gestation. Mares (n = 12) paired by stage of gestation (d 65 to 100) were assigned to diets (six per diet) consisting of endophyte-free (E-) or E+ tall fescue seed (50% E- or E+ tall fescue seed, 45% sweet feed, and 10% molasses fed at 1.0% of BW/d). Mares also had ad libitum access to E+ or E- annual ryegrass hay, and were fed diets for 10 d. Following removal from the tall fescue diet on d 11, mares were placed on common bermudagrass pasture and monitored until d 21. Morning and evening rectal temperatures were recorded and daily blood samples were collected for progesterone and prolactin (PRL) analyses, whereas samples for 3,4-dihydroxyphenyl acetic acid (a catecholamine metabolite) analysis were collected on alternate days. For clinical chemistry analysis, blood samples were collected on d 0, 5, 10 and 21. Daily urine samples were collected for ergot alkaloid analysis, and ultrasonography was performed for presence of echogenic material in fetal fluids. Rectal temperatures (E+ 37.76+/-0.03; E- 37.84+/-0.03 degrees C) and serum PRL concentrations (E+ 14.06< or =0.76; E- 12.11+/-0.76 ng/mL) did not differ (P = 0.96) between treatments. Measuring the change in basal serum concentration from d 0 over time, progesterone concentrations did not differ (-0.64 +/-1.49 and -0.55+/-1.47 ng/mL for E+ and E- mares, respectively). There was no negative pregnancy outcome, and ultrasonography indicated no increase in echogenic material in fetal fluids. Plasma 3,4-dihydroxyphenyl acetic acid concentrations decreased (P < 0.05) in E+ compared with E- mares (2.1+/-0.14 and 4.4+/0.43 ng/mL, respectively). Urinary ergot alkaloid concentration was greater (P < 0.01) in mares consuming E+ compared with E- (532.12+/- 52.51 and 13.36+/-2.67 ng/mg of creatinine, respectively). Although no fetal loss was observed during the current study, elevated concentrations of urinary ergot alkaloid were consistent with depressed endogenous catecholamine activity, suggestive of an endocrine disruptive effect of hypothalamic origin.

Noradrenergic and dopaminergic effects of (+)-amphetamine-like stimulants in the baboonPapio anubis

(+)-Amphetamine, (+/-)-ephedrine, and phentermine are commonly used appetite suppressants that release monoamines from nerve cells by acting as substrates for biogenic amine transporters. One key difference among the three drugs is their selectivity for norepinephrine (NE) release vs. dopamine (DA) release. The NE/DA selectivity ratios for these drugs as determined in vitro [(EC50 NE(-1))/(EC50 DA(-1))] are (+/-)-ephedrine (18.6) > phentermine (6.7) > (+)-amphetamine (3.5). The in vitro data suggest that when administered in vivo, these stimulants might differ in their ability to release DA from nerve terminals in the brain. To test this hypothesis, noradrenergic effects (i.e., plasma NE) and dopaminergic effects (i.e., central DA release) were assessed when each drug was administered intravenously (1.5 mg/kg) to anesthetized baboons. Central DA release was determined via positron emission tomography using the method of [11C]raclopride displacement. In the present investigation, high doses of these stimulants increased plasma NE and DA in parallel, but only (+)-amphetamine released central DA from neurons and decreased plasma prolactin. None of the drugs altered plasma amine metabolite levels, indicating no inhibition of monoamine oxidase activity at the administered doses. Plasma drug levels measured in baboons were higher than those measured in human patients taking prescribed doses of the drugs. Viewed collectively, the present data indicate that typical clinical doses of phentermine and (+/-)-ephedrine may not release central DA in humans, a hypothesis that should ultimately be tested in controlled clinical studies.

Basal and exercise-induced sympathetic nervous activity and lipolysis in adipose tissue of patients with anorexia nervosa

BACKGROUND

The sympathetic nervous system plays an important role in the regulation of adipose tissue (AT) lipolysis, which is a key step in the metabolic processes leading to the decrease of fat mass. The present study was designed to determine in vivo basal and exercise-stimulated lipolysis and concentrations of catecholamines, the major hormones controlling lipolysis, in subcutaneous abdominal AT in patients with anorexia nervosa (AN), characterized by self-induced starvation and excessive exercises resulting in severe malnutrition and fat store loss. The results of local catecholamines and glycerol levels were compared with those in plasma in both experimental groups.

MATERIAL AND METHODS

An in vivo microdialysis technique was used for the assessment of norepinephrine, dihydroxyphenylalanine, dihydroxyphenylacetic acid and glycerol concentrations in subcutaneous AT of 10 women with AN (body mass index: 15.57 +/- 0.55 kg m(-2)) and 10 age-matched controls (body mass index: 21.56 +/- 0.41 kg m(-2)). Both the AN patients and the control subjects underwent a 1.5 W kg(-1) exercise test.

RESULTS

Basal AT norepinephrine concentrations were increased in the AN patients in comparison with the controls. Basal AT glycerol concentrations were similar in both groups. During exercise, a local increase in the AT norepinephrine and glycerol concentrations was observed in the AN patients only. In contrast to the controls, the basal AT dihydroxyphenylalanine and dihydroxyphenylacetic acid levels in the AN patients were high and remained unchanged during exercise. Basal and exercise-stimulated plasma norepinephrine, dihydroxyphenylalanine, dihydroxyphenylacetic acid and glycerol levels were not different in the AN patients and healthy controls.

CONCLUSION

Our study provides evidence of elevated baseline and exercise-induced sympathetic nervous activity and exercise-induced lipolysis in abdominal AT of AN patients.

Quercetin, an over-the-counter supplement, causes neuroblastoma-like elevation of plasma homovanillic acid

A 22-month-old boy, who regularly consumed the oral dietary supplement, quercetin, was suspected erroneously of having a catecholamine-producing tumor, based on elevated serum and urine levels of the dopamine metabolite, homovanillic acid (HVA). Subsequent studies of healthy adult volunteers showed that significant elevations in plasma HVA are a consequence of quercetin ingestion.

Serotonin, serotonin 5-HT(1A) receptors and dopamine in blood peripheral lymphocytes of major depression patients

There are increasing evidences of cell markers present in the immune and the nervous systems. These include neurotransmitter receptors and transporters. Serotonin receptor subtypes are related to depression and also have been shown to be present in certain cells of the immune system. In the present report, we determined the presence of 5-HT(1A) receptors by the binding of the selective agonist 8-hydroxy-2-(di-n-propyl-amino)tetralin in lymphocytes of peripheral blood isolated by Ficoll/Hypaque gradients from controls and depressed patients. The capacity of these receptors was around 24 fmol/10(6) cells in both groups of subjects, without significant difference among them. The affinity was in the nM range and either differ between controls and patients. Serotonin, 5-hydroxyindoleacetic acid, dopamine and 3,4-dihydroxyphenylacetic acid were determined by HPLC with electrochemical detector. There were no significant differences between controls and major depression patients in the values obtained for rich and poor platelet plasma or in the isolated cells. However, there was a reduction in serotonin turnover rate indicated by an increase in the ratio serotonin/5-hydroxyindoleacetic acid, but not in that of dopamine, in lymphocytes of major depression patients. Thus, there is a serotonergic dysfunction in immune circulating cells of major depression patients, without changes in the number of 5-HT(1A) receptors, although the coupling of these receptors to transduction mechanisms could be affected and may be related to the alteration of 5-HT turnover rate.

Exaggerated adrenomedullary response to immobilization in mice with targeted disruption of the serotonin transporter gene

This study examined whether serotonin transporter (5-HTT) gene knockout influences adrenomedullary, sympathoneural, or hypothalamo-pituitary-adrenal responses to acute immobilization. In conscious, cannulated mice, arterial plasma concentrations of catecholamines, ACTH, and corticosterone were measured at baseline and after 15 min of immobilization. Tissue levels of serotonin (5-HT), catecholamines, and hormones were also measured in pituitary and adrenal glands. At baseline, adrenal and pituitary 5-HT concentrations in knockout (5-HTT(-/-)) mice were markedly lower than those in littermate control (5-HTT(+/+)) mice, whereas the groups did not differ in levels of catecholamines or hormones in plasma or tissue. Immobilization increased plasma levels of catecholamines, ACTH, and corticosterone in all genotypes. 5-HTT(-/-) mice had exaggerated responses of plasma epinephrine to immobilization and significant reductions in adrenal epinephrine, norepinephrine, and 5-HT contents compared with values in littermate controls. Pituitary ACTH was significantly reduced after immobilization in 5-HTT(-/-) mice only, but increases in plasma ACTH and corticosterone levels did not differ between genotypes. The results suggest that one 5-HTT function is to restrain adrenomedullary activation in response to immobilization. Exaggerated adrenomedullary responses seem to be an autonomic correlate of the anxiety-like behaviors in 5-HTT knockout mice.

Increases in plasma dihydroxyphenylacetic acid levels in decapitated mice after exposure to various stresses

This study investigated changes in plasma levels of the dopamine metabolite dihydroxyphenylacetic acid (DOPAC) in decapitated mice in response to the variable stresses of restraint, restraint and water immersion, and foot shock. DOPAC levels, but not norepinephrine (NE) and epinephrine (EPI) levels, increased upon exposure to these stresses. Plasma DOPAC levels measured using the decapitation method in rats were then compared with those measured using the catheter method. The NE and EPI levels in plasma measured using the decapitation method were much higher than those using the catheter method under basal conditions. In contrast, differences in the levels of DOPAC in plasma were smaller than those of NE and EPI under basal conditions using in both methods; furthermore parallel changes in plasma DOPAC levels occurred during restraint and water immersion stresses. These results indicate that the plasma DOPAC levels measured in mice using the decapitation method were clearly increased by the different stresses. Furthermore, in rats there were correlations between the decapitation and catheter methods for plasma levels of DOPAC. Thus the change in plasma DOPAC levels measured using the decapitation method is a good indicator of stress responses involving sympathoneural activity.

Monoamine metabolism and sympathetic nervous activation following subarachnoid haemorrhage: influence of gender and hydrocephalus

Subarachnoid haemorrhage is a serious condition, often accompanied by cerebral vasospasm and hydrocephalus, which may result in delayed cerebral ischaemia and neurological deterioration. While the mechanisms responsible remain unknown, activation of the sympathetic nervous system, leading to elevated levels of circulating catecholamines is, at least in part, implicated. In this study, we sought to examine the importance of sympathetic nervous activation and its relation to brain monoaminergic neurotransmission in 25 patients following subarachnoid haemorrhage by examining plasma and cerebrospinal fluid levels of the catecholamines noradrenaline, adrenaline and dopamine, and their metabolites. Total body sympathetic activity was concurrently assessed using isotope dilution methodology. In the early phase following subarachnoid haemorrhage patients exhibited markedly elevated rates of spillover of noradrenaline to plasma (9.11 +/- 1.12 vs. 3.39 +/- 0.26 nmol/min, p < 0.01), with rates being higher in those patients in whom hydrocephalus developed (11.15 +/- 1.40 vs. 7.90 +/- 1.41 nmol/min, p = 0.05). The degree of sympathetic nervous activation tended to be higher in females compared with males. Lower cerebral perfusion pressures were observed in those patients in whom cerebrospinal fluid concentrations of noradrenaline and dopamine metabolites were high. A marked sympathetic nervous activation, more pronounced in women and in those with hydrocephalus, occurs following subarachnoid haemorrhage. The diminished cerebral perfusion seen following subarachnoid bleeding may occur as a result of activation of central catecholaminergic neurones.

COMT-inhibition increases serum levels of dihydroxyphenylacetic acid (DOPAC) in patients with advanced Parkinson's disease

Inhibition of the catechol-O-methyltransferase (COMT) is an effective treatment for end-of-dose fluctuations in advanced Parkinson's disease. The aim of the present investigation was to analyse the consequences of subsequent alterations in levodopa metabolism under common treatment conditions when the levodopa dose is adjusted due to the occurrence of dyskinesias after initiation of the COMT-inhibitor. Ten patients with advanced Parkinson's disease (Hoehn & Yahr stage IV) were medicated with tolcapone. Prior to and five to ten days after the initiation of tolcapone 300 mg/d, serum level profiles of levodopa and its metabolites (3-O-methyldopa (3-OMD), dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA)) were performed. The mean daily levodopa dose was reduced from 894 +/- 248 mg to 646 +/- 252 mg (p = 0.003). There was a significant increase in the area under the curve (AUC) of DOPAC during COMT-inhibition compared to the baseline profile (p = 0.009). There were significant decreases of the AUC of HAV (p = 0.001) and the ratios of the AUC HVA / AUC DOPAC (p = 0.0001) and AUC 3-OMD / AUC levodopa (p = 0.0001).

CONCLUSION

The elevation of DOPAC and the decrease of HVA and HVA / DOPAC reflect a shift of the levodopa metabolism towards the MAO-B dependent oxidative pathway. This might contribute to production of hydroxyl radicals and induction of oxidative stress.

Evaluation of plasma 3,4-dihydroxyphenylacetic acid (DOPAC) and plasma 3,4-dihydroxyphenylalanine (DOPA) as tumor markers in children with neuroblastoma

Catecholamines and their metabolites are important in the diagnosis of neuroblastoma (NB). Plasma (p-) levels of 3,4-dihydroxyphenylalanine (DOPA) are increased in most NB, probably reflecting decreased DOPA decarboxylase activity. Urine (u-) homovanillic acid (HVA), a DOPA and dopamine (DA) metabolite. is also increased in most NB. DOPAC (3,4-dihydroxyphenylacetic acid) is an important metabolite of DA in tissues with monoamine oxidase (MAO) activity. Because MAO is expressed in NB tumor cells, we studied the importance of measuring p-DOPAC and p-DOPA as compared to u-HVA and u-vanillylmandelic acid (VMA) in the diagnosis and follow-up of NB. DOPAC, DOPA, dopamine, noradrenaline, adrenaline, VMA and HVA were measured by reverse-phase HPLC with electrochemical detection in 106 children (28 with NB (13 newly diagnosed), 25 with other solid tumors, 28 hospitalized for nonneoplastic diseases, and 25 healthy children). P-DOPAC or p-DOPA concentrations were above the upper normal range in 92% of untreated NB patients, as were u-HVA or u-VMA levels. None of these tumor markers was correlated to tumor stage or survival. P-DOPA but not p-DOPAC was correlated to age in NB children. Increased values of p-DOPAC and p-DOPA were found in one patient surviving NB for 10 years. Plasma DOPAC concentrations were decreased in children hospitalized for non-NB diseases, probably reflecting reduced food intake. Plasma analyses of DOPA and DOPAC seem to be useful alternatives in the diagnosis and follow-up of NB if urine sampling is to be avoided. Plasma DOPAC may be an index of nutritional status in various diseases.

Plasma hormones and catecholamine metabolites in monozygotic twins discordant for psychosis

OBJECTIVE

To examine plasma cortisol, adrencorticotropin hormone, and indicators of catecholamine activity in monozygotic twins discordant for schizophrenia or major affective disorders.

BACKGROUND

Previous research has suggested that catecholamines play a role in the etiology of major mental illness. Several findings have also shown an inverse relation between hippocampal volume and cortisol levels in psychiatric populations including patients who are depressed and patients with Cushing disease.

METHOD

In this study, plasma obtained from monozygotic twin pairs discordant for schizophrenia (n = 10) or major affective disorder (n = 3) was assayed for epinephrine, norepinephrine, dihydroxyphenylacetic acid, homovanillic acid, adrencorticotropin hormone, and cortisol.

RESULTS

There was significant concordance for levels of dihydroxyphenylacetic acid and homovanillic acid, consistent with the high concordance for indicators of dopamine activity observed in healthy monozygotic pairs. There was also concordance for adrencorticotropin hormone. However, in contrast to findings on healthy monozygotic pairs, there was no relation for epinephrine, norepinephrine, or cortisol. Among patients, there was an inverse correlation between cortisol and the magnitude of the reduction in hippocampal volume, relative to that of the healthy co-twin.

CONCLUSION

These findings suggest the potential role of adrenal steroids and hippocampal function in the expression of psychosis.

Antioxidative activity of 3,4-dihydroxyphenylacetic acid and caffeic acid in rat plasma

The purpose of the present paper is to study and compare in vitro the inhibitory effect of 3,4-dihydroxyphenylacetic acid (DOPAC) and caffeic acid (CA) on lipid peroxidation in rat plasma. Rat plasma was oxidized at 37 degrees C by the radical initiators 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) or 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (MeO-AMVN). The consumption of endogenous alpha-tocopherol (alpha-TOH) and the accumulation of conjugated diene hydroperoxides were measured by high-performance liquid chromatography and by ultraviolet spectroscopy, respectively. Alpha-TOH was consumed at the same rate in the presence of 20 mM AAPH or 2 mM MeO-AMVN. DOPAC and CA suppressed the alpha-TOH consumption in a dose-dependent manner. A concentration of 50 microM of both phenolic acids was sufficient to induce a lag phase and to delay the rate of alpha-TOH consumption. The effect was more pronounced in rat plasma oxidation by AAPH than by MeO-AMVN. CA spared vitamin E more effectively than DOPAC in both oxidations. DOPAC and CA suppressed the formation of conjugated diene hydroperoxides. DOPAC and CA at concentration 50 microM suppressed alpha-TOH consumption during oxidation of soybean phosphatidylcholine (2.8 mM) multilamellar vesicles containing 15 microM alpha-TOH, in which the lipophilic initiator 2,2'-azobis (2,4-dimethylvaleronitrile) (6 mM) was incorporated. In conclusion, we demonstrated that DOPAC and CA in micromolar concentrations have antioxidant activity in rat plasma, a medium very close to the conditions in vivo, suggesting that supplementation with the phenolic acids will provide significant antioxidant protection.

Susceptibility to subsequent episodes of spontaneous recurrence of methamphetamine psychosis

We examine susceptibility to subsequent spontaneous recurrences of methamphetamine psychosis (i.e. flashbacks) in 11 flashbackers with a single episode and in nine flashbackers with subsequent episodes. All had undergone frightening stressful experiences during previous MAP use. Mild psychosocial stressors then triggered flashbacks. During flashbacks, the nine flashbackers with subsequent episodes had more markedly increased norepinephrine levels, with slightly increased 3-methoxytyramine levels. The duration of imprisonment in this subgroup approached significantly long levels than in the 11 flashbackers with a single episode. Robust noradrenergic hyperactivity with slightly increased dopamine release may therefore predict subsequent flashbacks. Longer exposure to distressing situations may also contribute to robust noradrenergic hyperactivity.

Heart failure, aging, and renal synthesis of dopamine

The present study evaluates renal dopaminergic activity in 23 patients with heart failure (HF), 10 age-matched controls, and 10 young subjects during normal-salt (NS) intake and after 8 days of low-salt (LS) intake (patients with HF and age-matched controls only). LS intake produced a marked reduction in urine volume in patients with HF but failed to affect urine volume in age-matched controls. Urinary sodium and fractional excretion of sodium were markedly reduced by LS intake in patients with HF and age-matched controls. Daily urinary excretion of L-3,4-dihydroxyphenylalanine (L-dopa) and dopamine was lower in patients with HF than in age-matched controls. LS intake failed to alter L-dopa and dopamine urinary excretion in control subjects. In patients with HF, LS intake produced a significant decrease in urinary L-dopa excretion, but failed to alter the urinary excretion of dopamine. No significant differences were observed in urinary L-dopa, dopamine, and dopamine metabolite levels between aged controls and young healthy subjects. Urinary dopamine-L-dopa ratios in patients with HF on LS intake (24.5 +/- 7.1) were significantly greater than those with NS intake (11.6 +/- 1.3). Urinary dopamine-L-dopa ratios in old control subjects (LS, 9.7 +/- 1.3; NS, 9.3 +/- 1.1) did not differ from those in young healthy subjects (9.2 +/- 0.8). LS intake produced a marked increase in plasma aldosterone levels in both patients with HF (84.6 +/- 14.4 to 148.2 +/- 20.4 pg/mL; P = 0.0008) and controls (102.1 +/- 13.4 to 151.6 +/- 15.7 pg/mL; P < 0.04). Plasma norepinephrine levels were not significantly affected by LS intake in controls (5.1 +/- 1.62 to 6.3 +/- 1.6 pmol/mL; P = 0.22), but were significantly increased in patients with HF (5.8 +/- 0.8 to 7.1 +/- 0.9 pmol/mL; P = 0.04). In conclusion, patients with HF are endowed with an enhanced ability to take up (or decarboxylate) filtered L-dopa, which might counterbalance the reduced renal delivery of L-dopa, contributing to a relative preservation of dopamine synthesis. This may result as a compensatory mechanism, activated by stimuli leading to sodium reabsorption. Age seems to have no influence on renal dopamine production.

Inverse relationship between plasma epinephrine and testosterone levels during acute glucoprivation in healthy men

In healthy men, a decrease in plasma testosterone levels was observed in the context of metabolic stress. While physiological mechanisms underlying this response are unclear, there are several lines of evidence suggesting circulating epinephrine's influence on plasma testosterone levels. The purpose of this study was to directly relate stress-induced changes in plasma testosterone and epinephrine. The stressor used was blockade of glucose metabolism with pharmacological doses (40 mg/kg) of 2 deoxyglucose (2DG). Arterial plasma samples from 10 healthy males were assayed at 20 minutes intervals for 60 minutes for the concentrations of testosterone, epinephrine and related biochemicals. Bolus administration of 2DG resulted in progressive decline in testosterone and increases in epinephrine and norepinephrine plasma levels (mean change from baseline: 29, 2530 and 186%, respectively). Inverse correlation was detected between both absolute (r(s)=-0.72; df=8; p=0.017) and baseline-corrected testosterone concentrations at the 60 minute time point and epinephrine area under the curve values. Our results suggest that adrenomedullary activation may be involved in stress-induced testosterone effects. The implications of these data for the understanding of the role of catecholamines in glucoprivic stress response are discussed.

Autonomic ganglionic neurones in rabbits with differing resistance to emotional stress

The aim of the present study was to evaluate the reactions of autonomic neurones of the nodose ganglion of the vagus nerve, and the stellate and superior cervical ganglia in rabbits under emotional stress, and to correlate these reactions with the individual variations in responses to the stressor. Emotional stress was induced in immobilized adult male Chinchilla rabbits by electrical stimulation of the ventromedial hypothalamus and skin. During the experiment (3 hours) arterial blood pressure (BP) was recorded. Metabolic activities of the stellate and superior cervical sympathetic ganglia and nodose ganglion were measured as contents of biogenic amines and their synthesizing and degrading enzymes, neuronal size and dry mass and total RNA; these corresponded to the changes in BP. One group of rabbits showed small fluctuations of BP throughout the experiment and were defined as resistant to stress, whereas in the other group (predisposed to stress) BP progressively decreased. In the former, there was a smaller increase of sympathetic and nodose ganglia metabolic activity than in the latter, in which changes included reduced neuronal dry mass, increased RNA content compared with controls, and reduced tyrosine hydroxylase activity and increased norepinephrine content compare with controls and stress- resistant rabbits. The predisposed rabbits showed earlier and greater increases in circulating norepinephrine concentrations than the resistant rabbits, indicating sustained sympathetic activation. The data indicate that the ganglia of the sympathetic nervous system are part of a major mechanism of BP regulation under acute experimental emotional/painful stress. The nodose ganglion participates in the maintenance of stable cardiovascular function in extreme conditions.

Effects of chronic administration of sibutramine on body weight, food intake and motor activity in neonatally monosodium glutamate-treated obese female rats: relationship of antiobesity effect with monoamines

When the hypothalamic ventromedial nucleus and arcuate nucleus were destroyed in rats by treatment with monosodium glutamate in the neonatal stage, increase in the Lee index (body weight 1/3/body length) and in retroperitoneal fat as well as decreases in spontaneous motor activity, food consumption and growth hormone secretion function associated with hypothalamic low body length obesity (monosodium glutamate-treated obesity; MSG-OB) were observed as these rats grew. Treatment with sibutramine at 3 and 10 mg/kg p.o. once a day continuously for 14 days improved these parameters, and the degree of improvement was dose related. The plasma lipid values in MSG-OB rats, which were the same as those in normal rats, were decreased by consecutive administration of sibutramine. Levels of hypothalamic monoamines (MAs) such as norepinephrine, 5-HT (serotonin) and dopamine and their metabolites DOPAC, HVA and 5-HIAA were decreased in MSG-OB rats, and further decrease in them, though slight, was observed with consecutive daily administration of sibutramine, probably as a result of the feedback attributable to an increase in MA in synapses caused by inhibition of MA uptake by sibutramine. These results suggest that sibutramine can activate the MA nervous system by MA uptake inhibition in regions of the brain such as the lateral hypothalamic area and the paraventricular nucleus, which control food intake and sympathetic nerve activity, and the nigrostriatal area related to the extrapyramidal motor system, and thereby exhibit anti-obesity effects in the MSG-OB rat.

The effects of central aromatic amino acid DOPA decarboxylase inhibition on the motor actions of L-DOPA and dopamine agonists in MPTP-treated primates

1. Endogenous L-DOPA may act as a neuromodulator contributing to the production of motor activity. We now investigate the effects of the centrally acting aromatic amino acid dopa decarboxylase (AADC) inhibitor NSD-1015 (3-hydroxybenzyl hydrazine) on the motor actions of L-DOPA and dopamine agonist drugs in MPTP treated common marmosets. 2. Pretreatment with NSD-1015 (10 - 50 mg kg(-1); i.p.) worsened baseline motor deficits in MPTP-treated common marmosets. Similarly, it abolished L-DOPA (5 - 18 mg kg(-1) s.c.) induced locomotor activity and reversal of disability. NSD-1015 pretreatment inhibited dopamine formation and elevated L-DOPA levels in plasma. 3. The increase in locomotor activity and improvement in disability produced by the administration of the D-1 agonist A-86929 (0.03 - 0. 04 mg kg(-1) s.c.) or the D-2 agonist quinpirole (0.05 - 0.3 mg kg(-1) i.p.) was abolished by NSD-1015 (25 mg kg(-1) i.p.) pretreatment. While the effects of a low dose combination of A-86929 (0.04 mg kg(-1) s.c.) and quinpirole (0.05 mg kg(-1) i.p.) were inhibited by NSD-1015 (25 mg kg(-1) i.p.), there was little effect on the action of a high dose combination of these drugs (0.08 mg kg(-1) A-86929 and 0.1 mg kg(-1) quinpirole). 4. Following central AADC inhibition with NSD-1015 (25 mg kg(-1) i.p.), locomotor behaviour induced by administration of high dose combinations of A-86929 (0.08 mg kg(-1) s.c.) and quinpirole (0.1 mg kg(-1) i.p.) was unaffected by L-DOPA (5 mg kg(-1) s.c.) pretreatment. 5. These results do not support a role for endogenous L-DOPA in spontaneous or drug induced locomotor activity. Rather, they strengthen the argument for the importance of endogenous dopaminergic tone in the motor actions of dopamine agonists.

A simple high-performance liquid chromatography assay for simultaneous determination of plasma norepinephrine, epinephrine, dopamine and 3,4-dihydroxyphenyl acetic acid

A reversed-phase HPLC assay coupled with electrochemical detection for simultaneously measuring plasma levels of norepinephrine, epinephrine, dopamine, and 3,4-dihydroxyphenylacetic acid (DOPAC) was developed. Separation of the catecholamines and the internal standard isoproterenol was obtained by a mobile phase consisting of 7% methanol in 0.1 M citrate buffer containing 0.3 mM sodium ethylenediaminetetraacetic acid (EDTA), and 0.5 mM 1-octanesulfonic acid, operated under isocratic condition at a flow rate of 1.2 ml/min. The potential of the guard cell was set at +650 mV, the first electrode of the analytical cell at +100 mV and the second at + 350 mV. Using a signal-to-noise ratio of > 3, the minimum detection limit assessed by direct on column injection was < 10 pg for analyte. The assays were linear from basal concentrations to 400 ng/ml. The intra- and inter-assay variations were < 10 and 15%, respectively. The assay has been applied successfully to measure plasma concentrations of these catecholamines in humans, rabbits and rats.

Alpha2-adrenoceptor-mediated restraint of norepinephrine synthesis, release, and turnover during immobilization in rats

Stress-related release of norepinephrine (NE) in the brain and periphery probably underlies several neuroendocrine and neurocirculatory responses. NE might influence its own synthesis, release, and turnover, by negative feedback regulation via alpha2-adrenoceptors. We examined central and peripheral noradrenergic function by measuring concentrations of NE, dihydroxyphenylglycol (DHPG), and dihydroxyphenylacetic acid (DOPAC) in hypothalamic paraventricular nucleus (PVN) microdialysate and arterial plasma simultaneously during immobilization (IMMO) in conscious rats. The alpha2-adrenoceptor antagonist yohimbine (YOH) was injected i.p. or perfused locally into the PVN via the microdialysis probe. The i.p. YOH increased plasma NE, epinephrine (EPI), DHPG, dihydroxyphenylalanine, and DOPAC levels by 4.3, 7.3, 2.5, 0.6 and 1.8-fold and PVN microdialysate NE, DHPG, and DOPAC by 1. 2, 0.6 and 0.5-fold. The i.p. YOH also enhanced effects of IMMO on plasma and microdialysate NE, DHPG, and DOPAC. YOH delivered via the PVN microdialysis probe did not affect microdialysate or plasma levels of the analytes at baseline and only slightly augmented microdialysate NE responses to IMMO. The results indicate that alpha2-adrenoceptors tonically restrain NE synthesis, release, and turnover in sympathetic nerves and limit IMMO-induced peripheral noradrenergic activation. In the PVN, alpha2-adrenoceptors do not appear to contribute to these processes tonically and exert relatively little restraint on IMMO-induced local noradrenergic activation.

Nitric oxide plays an important role in the diurnal change of tuberoinfundibular dopaminergic neuronal activity and prolactin secretion in ovariectomized, estrogen/progesterone-treated rats

A significant diurnal change of tuberoinfundibular dopaminergic (TIDA) neuronal activity coincident with the estrogen (E2)-induced afternoon PRL surge has been reported in ovariectomized, E2-primed (OVX+E2) rats. Systemic injection of a nitric oxide (NO) synthase (NOS) inhibitor, N(G)-nitro-L-arginine (L-NA, 50 mg/kg, i.p. at 1000 and 1200 h), significantly blocked the diurnal changes of TIDA neuronal activity and PRL secretion at 1500 and 1700 h in OVX+E2 rats. Coadministration of L-arginine (300 mg/kg, i.p.) with L-NA completely prevented the effects of L-NA. Total nitrite/nitrate levels in the serum of L-NA- and L-NA+L-arginine-treated rats substantiated the effects of L-NA and L-arginine on NO production. Pretreatment of antisense oligodeoxynucleotide (ODN; 1 microg/3 microl; intracerebroventricularly at 48, 24, and 7 h before sacrifice) against the messenger RNA (mRNA) of constitutive NOS, i.e. neuronal NOS or endothelial NOS, was also effective in preventing the diurnal changes of TIDA neuronal activity and PRL surge at 1500 h. The same treatment of antisense ODN against the mRNA of inducible NOS, i.e. macrophage NOS, had no effect. Progesterone (P4) has been reported to advance and augment the diurnal changes of TIDA neuronal activity and the afternoon PRL surge, by 1 h, in both proestrous and OVX+E2 rats. We further showed that L-NA dose dependently (50 but not 5 mg/kg, i.p. at 1000 and 1200 h) blocked the effect of P4 on TIDA neurons and serum PRL at 1300 h, which effect could be negated by simultaneous administration of L-arginine (300 mg/kg, i.p.). Pretreatment with antisense ODNs against the mRNA of neuronal NOS or endothelial NOS, but not macrophage NOS, was also effective in preventing the P4's effect on TIDA neuronal activity and PRL secretion at 1300 h. In summary, NO may play a physiological role in the E2- and P4-regulated diurnal changes of TIDA neuronal activity and PRL secretion.

Differential catecholamine responses to protein intake in healthy and hypertensive subjects

Protein intake-induced natriuresis previously related to increased urinary dopamine excretion was reexamined in an extensive controlled study comparing healthy and hypertensive subjects. In healthy subjects, ingestion of 1 g/kg wt tuna induced natriuresis that was associated, between postprandial hours 1 and 2, with increased plasma tyrosine [191 +/- 13% (mean +/- SE); P < 0.01], 3, 4-dihydroxyphenylalanine (104 +/- 12%, P < 0.05 in plasma; 162 +/- 20%, P < 0.05 in urine), plasma free dopamine (156 +/- 32%; P < 0. 05), and dopamine sulfate (191 +/- 11%, P < 0.001 in plasma; 199 +/- 15%, P < 0.01 in urine) but affected urinary free dopamine excretion only at limits of significance. Hypertensive subjects had less (P < 0.02) natriuresis and, despite comparable plasma tyrosine and dopamine sulfate increases, no increase in plasma and urinary 3, 4-dihydroxyphenylalanine and plasma free dopamine. Their plasma and urinary free epinephrine responses were less (P < 0.05) than the borderline increases in control subjects. Compared with control subjects, they significantly increased plasma 3, 4-dihydroxyphenylalanine sulfate (P < 0.05), epinephrine sulfate (P < 0.05), and the dopamine sulfate-to-free dopamine ratio (P < 0.02). Postprotein natriuresis is thus associated with nutritional priming-induced plasma but not urinary free dopamine increase. Hypertensive subjects have attenuated natriuretic and plasma free dopamine responses and less free epinephrine increase. This may partly result from higher circulating 3,4-dihydroxyphenylalanine, dopamine, and epinephrine sulfoconjugates leaving fewer free amines for biological actions.

The effects of branched chain amino acid infusion on pain perception and plasma concentrations of monoamines

Infusions of branched chain amino acids (BCAA) have been shown to have several CNS-mediated effects including antinociceptive action. We investigated the effects of BCAA infusion on pain perception, respiratory control, and plasma monoamine concentrations. Six healthy female volunteers were given in a double-blind, random, crossover design an 8-h infusion (1.75 ml/kg/h) of either (a) Ringers lactate, (b) conventional 4% amino acid solution, or (c) 4% BCAA solution with intervals of at least 48 h. Respiratory control was evaluated with continuous capnography. Pain perception was measured using dental dolorimetry for sharp pain, and pain transmitted by afferent C-fibers was evaluated with tourniquet test. Changes in vigilance were measured using critical flicker fusion technique. Evaluations were made for baseline, and after 2.5, 5, and 8 h. Plasma samples were collected at the same time points for amino acid and monoamine analysis. BCAA infusion resulted in significant increases of plasma concentrations of all BCAAs, with a simultaneous decrease in concentrations of aromatic amino acids. Of the measured monoamines and their metabolites dihydroxyphenylacetic acid (DOPAC) decreased, showing significant treatment effect for BCAA. Despite these changes no significant effect of BCAAs on respiratory control, vigilance, or pain perception was observed. In conclusion, despite significant changes in plasma concentrations of both amino acids and DOPAC, BCAA infusion did not show any clinically relevant antinociceptive effect.

Pharmacokinetic and pharmacodynamic interactions between fluoxetine and moclobemide in the investigation of development of the "serotonin syndrome"

OBJECTIVE

To assess the tolerability, safety, pharmacokinetics, and pharmacodynamics of combined treatment with fluoxetine and moclobemide in healthy subjects.

METHODS

Fluoxetine (20 to 40 mg/day) was administered for 23 days to 18 subjects. At (nor)fluoxetine steady state, subjects were randomized in a 2:1 ratio to receive in addition either moclobemide (ascending doses up to 600 mg/day) of placebo. A single 300 mg dose of moclobemide was administered before and at the end of the fluoxetine regimen to assess the effects of the latter on the pharmacokinetics and pharmacodynamics of moclobemide. Adverse events and vital signs were recorded and pharmacokinetic parameters of fluoxetine and moclobemide were determined. Plasma concentrations of 3,4-dihydroxy-phenyl-glycol, 5-hydroxyindoleacetic acid, 3,4-dihydroxyphenylacetic acid, and serotonin uptake into platelets were assessed as pharmacodynamic measures.

RESULTS

The number, intensity, or type of adverse events did not change when moclobemide was added to fluoxetine. No clinically relevant changes in safety parameters occurred. Fluoxetine markedly inhibited the metabolism of moclobemide. However, multiple dosing of moclobemide did not lead the excessive accumulation. 3,4-Dihydroxyphenylglycol, 5-hydroxyindoleacetic acid, and 3,4-dihydroxyphenylacetic acid plasma levels and serotonin uptake did not reveal a pharmacodynamic interaction.

CONCLUSIONS

Combination treatment with fluoxetine and moclobemide did not provide any indication of development of the "serotonin syndrome."

Monitoring of blood catecholamines by microdialysis and microbore LC with a dual amperometric detector

The accuracy of in vivo microdialysis for monitoring blood catecholamines and their metabolites in Lan-Yu mini-pigs was evaluated. To prevent blood clots and irritation, a microdialysis probe was secured in a Y-shaped tube. The tube was connected to an arterio-venous shunt, in a mini-pig, for in vivo experiments. Perfusates were injected onto a microbore LC equipped with a dual electrochemical detector (the upstream electrode was set at an oxidizing potential and the downstream electrode was set at a reducing potential. The typical large offscale peak or interfering peaks on the anodic chromatograms were mostly eliminated on the cathodic chromatograms, thereby providing reliable measurements of early eluters. Early eluates, such as norepinephrine and epinephrine, with reversible redox behaviour could be detected at the downstream reducing electrode. A comparison of the present method and a conventional blood-drawing method showed good correlation (r = 0.775-0.983 for all analytes).

Chronic blockade of nitric oxide synthesis elevates plasma levels of catecholamines and their metabolites at rest and during stress in rats

Formation of nitric oxide, and endothelium-derived relaxing factor, can be inhibited by administration of N-nitro-L-arginine methylesther (L-NAME). In the present study, the activity of the sympathoadrenal system in rats with blood pressure (BP) elevation induced by L-NAME was investigated. L-NAME was administered in a dose of 50 mg/kg, i.p. every 12 h for 4 days. Blood samples were collected via chronically inserted arterial catheters in conscious, freely moving rats at rest and during immobilization stress. Plasma epinephrine (EPI), norepinephrine (NE), and dopamine (DA), as well as catecholamine metabolites dihydroxyphenylglycol (DHPG) and dihydroxyphenylacetic acid (DOPAC) were measured by HPLC method. In L-NAME treated animals, which slowed a significant increase in BP, plasma EPI levels were markedly elevated both before and during stress. Plasma NE levels were not significantly increased, however, DHPG levels, which indicate NE turnover and reuptake, were highly elevated. Plasma DA levels were not changed after L-NAME administration but DA metabolite DOPAC showed a significant elevation both under basal conditions and during stress. Thus, the present results indicate that the prolonged blockade of nitric oxide synthesis that causes arterial hypertension is associated with an activation of the sympathoadrenal system.

Pharmacodynamics of benserazide assessed by its effects on endogenous and exogenous levodopa pharmacokinetics

AIMS

The objectives of the study were to investigate the pharmacodynamics of the peripheral decarboxylase inhibitor benserazide during multiple-dose regimens.

METHODS

Two groups of eight healthy male subjects were consecutively treated for periods of 14 days with benserazide 5, 25, 100 mg three times daily and 12.5, 50, 200 mg three times daily, respectively. Plasma levels of levodopa, 3-O-methyldopa (3-OMD) and 3,4-dihydroxyphenylacetic acid (DOPAC) were determined before benserazide treatment and during all benserazide dosing regimens, as existing endogenously and after administration of 250 mg levodopa.

RESULTS

Endogenous concentrations of levodopa and 3-OMD increased dose-dependently (from 8 up to 52 microg l(-1) and from 0.02 up to 0.50 mg l(-1) , respectively, at doses of 200 mg) with ascending doses of benserazide whereas DOPAC levels remained unchanged. There were no indications of a plateau in the effects of benserazide on the plasma levels of the analytes. The area under the concentration-time curve (AUC) of exogenously administered levodopa increased from 1.2 in the control group to 5.9 mg l(-1) h at benserazide doses of 100-200 mg three times daily. Benserazide caused a dose-dependent increase in the AUC of 3-OMD from 7.4 to 106 mg l(-1) h at doses of 200 mg. Formation of DOPAC was dose-dependently suppressed, with benserazide 5 mg three times daily already halving its AUC.

CONCLUSIONS

The benserazide-dose response data obtained suggest that even at very high doses extracerebral decarboxylase is not yet completely inhibited.

Long-term reciprocal changes in dopamine levels in prefrontal cortex versus nucleus accumbens in rats born by Caesarean section compared to vaginal birth

Epidemiological evidence indicates a higher incidence of pregnancy and birth complications among individuals who later develop schizophrenia, a disorder linked to alterations in mesolimbic dopamine (DA) function. Two birth complications usually included in these epidemiological studies, and still frequently encountered in the general population, are birth by Caesarean section (C-section) and fetal asphyxia. To test the hypothesis that birth complications can produce long-lasting changes in DA systems, the present study examined the effects of Caesarean birth, with or without an added period of anoxia, on steady state monoamine levels and metabolism in various brain regions in a rat model. Pups born vaginally served as controls. At 2 months of age, in animals born by rapid C-section, steady state levels of DA were decreased by 53% in the prefrontal cortex and increased by 40% in both the nucleus accumbens and striatum, in comparison to the vaginally born group. DA turnover increased in the prefrontal cortex, decreased in the nucleus accumbens, and showed no significant change in the striatum, in the C-section group. Thus, birth by a Caesarean procedure produces long-term reciprocal changes in DA levels and metabolism in the nucleus accumbens and prefrontal cortex. This is consistent with the known inhibitory effect of increased prefrontal cortex DA activity on DA release in the nucleus accumbens. By contrast to birth by rapid C-section alone, young adult animals, that had been born by C-section with 15 min of added anoxia, showed no change in steady state DA levels in the prefrontal cortex, nucleus accumbens, or striatum and a significant decrease in DA turnover only in the nucleus accumbens, in comparison to the vaginally born group. Levels of norepinephrine, serotonin, and its metabolite, 5-hydroxyindole acetic acid, were unchanged in all groups, indicating relatively specific effects on DA systems. Although appearing robust at birth on gross observation, more subtle measurements revealed that rat pups born by C-section show altered respiratory rates and activity levels and increased levels of whole brain lactate, suggestive of low grade brain hypoxia, during the first 24 h of life, in comparison to vaginally born controls. Pups born by C-section with 15 min of added acute anoxia were pale, hypotonic, and inactive at birth and showed reduced respiration and high brain lactate levels. However, these alterations resolved by 1-5 h after birth and, with few exceptions, animals in the anoxic group remained normal with respect to these parameters during the remainder of the first 24 h of life. Immediately after birth, levels of plasma epinephrine, a hormone known to play a role in neonatal adaptation to extrauterine life and protection against hypoxia, were decreased in pups born by C-section but increased in pups born by C-section with 15 min added anoxia, in comparison to levels measured in vaginally born controls. These early developmental alterations could contribute to long-term alterations in dopaminergic parameters observed in rats born by C-section, with or without added anoxia. It is concluded that C-section birth is sufficient perturbation to produce long-lasting effects on DA levels and metabolism in the central nervous system of the rat. These findings highlight the sensitivity of DA pathways to variations in birth procedure and support the notion that birth complications might contribute to the pathophysiology of disorders involving central dopaminergic neurons, such as schizophrenia.

Effects of ordinary meals on plasma concentrations of 3,4-dihydroxyphenylalanine, dopamine sulphate and 3,4-dihydroxyphenylacetic acid

1. Plasma concentrations of 3,4-dihydroxyphenylalanine (DOPA), dopamine sulphate (DA-S), and 3,4-dihydroxyphenylacetic acid (DOPAC) in humans have been claimed to be indexes of sympathetic nervous activity, but the source and significance of plasma DOPA, DOPAC and DA-S have not been completely elucidated. 2. The effects of ordinary meals on plasma concentrations of total dopamine, mainly DA-S, DOPAC and DOPA were studied in seven healthy subjects. Venous blood was collected every hour for 25 h, while subjects were either fasting or received three meals at 9.00 hours, 13.00 hours and 18.00 hours. Catecholamines and metabolites were determined by reverse-phase HPLC with electrochemical detection. Neutral amino acids were measured by ion-exchange chromatography with photometric detection. 3. The food contained relatively little DOPA as compared with phenylalanine, tyrosine, isoleucine and tryptophan. The content of DA and DA-S varied considerably, with the greatest amount in the evening meal of open sandwiches. 4. Plasma DOPA decreased significantly after the meals at 13.00 hours and 18.00 hours, whereas concentrations of the other amino acids increased as expected. 5. Plasma DA-S increased significantly after meals and especially after the evening meal. Increments in DA-S above basal values after a meal were closely related to the content of DOPA+DA+DA-S in the meal. Plasma DOPAC increased significantly after the evening meal. 6. The decrease in plasma DOPA observed after a meal was probably due to uptake of DOPA by muscle tissue. Changes in plasma DA-S and DOPAC during this 25-h study reflected to a large extent the content of DOPA, DA and DA-S in the meals.

Plasma sulfoconjugated dopamine levels are normal in patients with autonomic failure

Plasma levels of norepinephrine (NE), dihydroxyphenylglycol (DHPG), dihydroxyphenylalanine (DOPA), dopamine (DA), and dihydroxyphenylacetic acid (DOPAC)--all of which are free catechols--and sulfoconjugated DA (DASO4) were determined in 14 normal subjects and 18 patients with neurogenic orthostatic hypotension caused by either multiple system atrophy (MSA) (n = 11) or pure autonomic failure (n = 7). All free catechols were normal in patients with MSA, whereas NE, DHPG, DA, and DOPAC levels were significantly lower in patients with pure autonomic failure. The levels of DA-SO4, however, did not statistically differ among the three groups. The different plasma levels of free catechols in MSA and pure autonomic failure are consistent with the view that peripheral sympathetic neurons are relatively preserved in MSA, whereas they are severely affected in pure autonomic failure. Because DASO4 does not appear to be affected in pure autonomic failure, it appears likely that this metabolite is derived mainly from non-neural sources, such as the gastrointestinal tract, rather than from the sympathoadrenomedullary system.

Initial monoamine oxidase-A inhibition by moclobemide does not predict the therapeutic response in patients with major depression. A double blind, randomized study

It is generally accepted that the clinical efficacy of monoamine oxidase inhibitors (MAOI) is related to inhibition of this enzyme. In order to evaluate the predictive ability of monoamine oxidase-A inhibition for therapeutic efficacy, the start of treatment effects of moclobemide, a selective, reversible monoamine oxidase-A inhibitor, on plasma concentrations of monoamines and monoamine metabolites were determined. The plasma levels of 3,4-dihydroxyphenylglycol (DHPG, deaminated metabolite of noradrenaline), 5-hydroxyindoleacetic acid (5-HIAA, deaminated metabolite of serotonin), 3,4-dihydroxyphenylacetic acid and homovanillic acid (DOPAC and HVA, deaminated metabolites of dopamine), L-dihydroxyphenylalanine (L-dopa) and noradrenaline were investigated and related to treatment outcome. This was a randomized double blind parallel group study in 47 patients with criteria of major depression according to DSM III R. Moclobemide 300 mg/day, 450 mg/day or 600 mg/day was administered continuously for 6 weeks. Plasma concentrations of monoamine metabolites and monoamines were determined just before treatment by moclobemide, 4 h after the first dose, 24 h after the first dose, before the first dose on day 7, and 4 h after the first dose, on day 7. Each moclobemide dose improved depression as measured by MADRS (Montgomery-Asberg Depression Rating scale) but there was no difference between the three doses. Moclobemide dose-dependently reduced plasma concentration of DHPG, L-dopa and HVA. No dose-dependent treatment effect was observed for plasma 5-HIAA, noradrenaline and DOPAC. The clinical outcome as defined by the final MADRS score was not related to any start of treatment changes in plasma monoamine metabolites reflecting inhibition of MAO-A. It is concluded that monoamine oxidase-A inhibition at the beginning of the treatment does not predict clinical outcome.

Pharmacokinetic-pharmacodynamic interactions between two selective monoamine oxidase inhibitors: moclobemide and selegiline

The objectives of this study were to assess potential pharmacokinetic and pharmacodynamic interactions between moclobemide and selegiline. Two groups of 12 healthy male and female subjects were treated with 200 mg moclobemide or 5 mg selegiline b.i.d. for 16 days. On study day 8, the alternative active drug or placebo was added to the respective treatments. Concentration-time profiles of moclobemide and two of its main metabolites and 3,4-dihydrox/phenylglycol (DHPG, a norepinephrine metabolite), 5-hydroxy-indoleacetic acid (HIAA, a serotonin metabolite), and 3,4-dihydroxyphenylacetic acid (DOPAC, a dopamine metabolite) in plasma as well as MAO-B activity and serotonin concentration in platelets were determined at steady state during monotreatment and combined treatment. The pharmacokinetic parameters of moclobemide and its metabolites changed on multiple dosing but were not influenced to a relevant extent by concomitant administration of selegiline. The measured pharmacodynamic parameters, expressed as the maximum effect on a study day and the area under the effect-time curve, characterized the drugs' influence on peripheral neurotransmitter metabolism. The most reliable variables to assess inhibition of MAO-A and -B in humans proved to be DHPG in plasma and serotonin in platelets and MAO-B activity in platelets, respectively. Several variables (DHPG, platelet serotonin) suggested that selegiline has some MAO-A inhibitory activity. This became particularly apparent upon addition of selegiline to moclobemide treatment; i.e., the effects of combined moclobemide and selegiline treatment were statistically greater than those of moclobemide monotreatment. Moclobemide alone exerted a slight inhibition of platelet MAO-B activity. The reported pharmacodynamic interactions are not considered to be clinically relevant. However, due to the previously found supraadditive tyramine potentiation upon simultaneous treatment, moclobemide and selegiline should only be combined when applying dietary restrictions with respect to tyramine.

Role of dopamine in the secretory function of corpus luteum in cattle

To investigate the role of dopamine (DA) in the secretion of progesterone and ovarian oxytocin (OT) in cattle in vivo and in vitro studies were performed. Luteal slices (middle stage of the luteal phase) were incubated-with five different amounts of DA (10(-3)-10(-7) M) and after 1, 2 and 4 h medium was collected for the progesterone and OT determination. The only 10(-5) M of DA enhanced OT medium concentrations (P < 0.05-0.001) and this response increased within duration of the incubation. The same dose of DA affected (P < 0.05-0.001) progesterone release during the incubation period. Next we wanted to study whether this mechanism will operate in conscious cattle. Mature heifers had cannulae inserted into the aorta abdominalis through the coccygeal artery for local infusion of saline or drugs, and into the jugular vein and the cava vena caudalis for the blood sample collection. In Experiment 2 six heifers on days 10-12 of the cycle received in Latin square design DA (8.4 micrograms/kg/min) for 2h, and they were pre-treated for 2 h with saline or for 1 h with droperidol (DROP; 1 microgram/kg/min) or with 4 micrograms/kg/min of beta-blocker, propranolol (PROP). DA increased (P < 0.05) OT plasma concentrations in all groups but secretion of progesterone was not changed (P > 0.05). DA decreased prolactin concentrations if pre-infused with saline and PROP and DROP diminished this effect of DA. Data suggest that DA affected OT release from both pituitary and from the ovary. Hence in Experiment 3 we wanted to elucidate whether DA caused those effects itself of after its conversion to the noradrenaline (NA). DA was given in six heifers as in Experiment 2 and blood samples were taken simultaneously from the vena cava and from the jugular vein. Within a few minutes from the start of DA infusion, large amount of DOPAC was measured by HPLC in blood. Next NA increase (P < 0.01) was observed in both veins but it was always higher (P < 0.05) in the vena cava. However, OT concentration in blood samples from both veins was not different (P > 0.05). Data indicate that DA can stimulate the secretory function of CL in cyclic heifers supposedly after its conversion to NA.

Circadian phase dependent pharmacokinetics of L-dopa, its main metabolites (3-OMD, HVA, DOPAC) and carbidopa in rats

This study aims to evaluate whether or not the kinetics of L-dopa, its main metabolites (3-O-methyldopa, 3-OMD, homovanilic acid, HVA and 3,4-dihydroxyphenylacetic acid, DOPAC) and carbidopa, vary according to the 24-hour scale in rats. Four groups of seven adult male Wistar AF EOPS rats were used for these experiments; each group received L-dopa (200 mg.kg-1 ip) and carbidopa (20 mg.kg-1 ip) at 1000, 1600, 2200 or 0400 hours. L-dopa, 3-OMD, DOPAC, HVA and carbidopa were simultaneously determined by specific ion-pair reversed-phase high performance liquid chromatography with electrochemical detection. A temporal variation of the kinetics of both L-dopa and carbidopa was demonstrated with higher plasma clearance and lower area under concentration curve after the administration at 2200 hours. Moreover, a temporal variation of the metabolism of L-dopa was indirectly documented by temporal variation in kinetics of 3-OMD, DOPAC and HVA.

Determination of 3,4-dihydroxyphenylacetic acid and 5-hydroxyindoleacetic acid in human plasma by a simple and rapid high-performance liquid chromatography assay

In order to study the pharmacodynamic effects of drugs on dopamine and serotonin metabolism, a reversed-phase HPLC assay coupled with electrochemical detection (ECD) for measuring plasma concentrations of 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindoleacetic acid (5-HIAA) was developed. The system was operated isocratically using a mobile phase of aqueous 0.03 M KH2PO4 buffer containing 0.15 mM EDTA in methanol (8.75:1.25), with a final pH of 4.0. The flow rate was set at 1.5 mL/min, and potentials at +450 mV. Using a signal to noise ratio of > 3, the minimum detection limit assessed by direct on-column injection of a standard solution for DOPAC and 5-HIAA was < 1 pg. The assays were linear from basal concentrations (1-10 ng/mL) to 100 ng/mL. The intra- and interassay variations were < 10% and < 20%, respectively.

Plasma catechols and monoamine oxidase metabolites in untreated Parkinson's and Alzheimer's diseases

Prior studies have documented functional and pathological compromise of the peripheral sympathetic nervous system in patients with Parkinson's disease, suggesting the possibility of reduced catecholamine release into the circulation. We measured free plasma catechols in early and untreated patients with Parkinson's disease, but found no evidence of reduced concentrations, compared to control subjects or a group of patients with probable Alzheimer's disease. Rather, there was a significant elevation of plasma norepinephrine within the Parkinson's disease group. Furthermore, 6 of 15 untreated Parkinson's disease patients (40%) displayed markedly elevated plasma concentrations of the catecholamine MAO metabolites, DOPAC or DOPEG. Despite this finding, platelet MAO-B activity measured in these and all other Parkinson's disease patients fell well within the range of the control subjects, and was also statistically similar to the group with Alzheimer's type dementia. Plasma dopa levels were similar in all groups, whereas the majority of patients in the three groups had plasma free dopamine and epinephrine concentrations below the limits of detection. These trends toward increased, rather than decreased, circulating catechol concentrations suggest that peripheral sympathetic nervous system catecholamine production and release is not severely compromised in patients with early Parkinson's disease. In addition, we were unable to confirm certain previous reports of elevated MAO-B activity in patients with Parkinson's or Alzheimer's diseases.

Levodopa and deprenyl treatment effects on peripheral indices of oxidant stress in Parkinson's disease

The oxidant stress theory of Parkinson's disease (PD) hypothesizes that levodopa treatment may be potentially harmful and this is supported by studies demonstrating levodopa toxicity to cultured dopaminergic neurons. These in vitro experiments, however, lack the physiologic protective mechanisms present in vivo. Oxyradical damage to cell membranes liberates malondialdehyde, which we measured in the serum of 27 PD patients just before and after levodopa (with carbidopa) administration. We also measured plasma products of the two routes by which levodopa potentially generated oxyradicals: (1) 5-S-cysteinyl-dopa (derived from levodopa autoxidation), and (2) 3,4-dihydroxyphenylacetic acid (DOPAC), produced by monoamine oxidase (MAO) metabolism of dopamine. Following levodopa/carbidopa administration, both of these plasma products were markedly increased; however, the mean serum malondialdehyde concentration was unchanged and remained similar to the normal control group (N=15) value. Chronic treatment with the MAO-B inhibitor, deprenyl (N=16), was not associated with any differences in serum malondialdehyde or plasma 5-S-cysteinyl-dopa concentrations compared with those not treated with deprenyl (N=11). The post-levodopa rise of plasma DOPAC was only slightly attenuated with deprenyl therapy, consistent with a predominant MAO-A effect in the circulation and peripheral organs. Thus, in contrast to in vitro studies, we did not detect evidence of oxidative damage in the circulation following levodopa administration, despite marked increase in the products of dopamine oxidative metabolism.