MONOAMINES (SEROTONIN AND CATECHOLAMINES) AND THEIR DERIVATIVES IN INFANTILE AUTISM: AGE-RELATED CHANGES AND DRUG EFFECTS

Levels of dopamine (DA) and its derivatives homovanillic acid (HVA), 3-4 dihydroxyphenylacetic acid (DOPAC), 3-methoxytyramine (3MT) and norepinephrine+epinephrine (NE + E), and serotonin (5HT) and its derivative 5-hydroxyindolacetic acid (5HIAA) were determined from the urine of 156 autistic children aged two to 12 years 6 months, and compared with those of age-matched mentally retarded non-autistic and normal controls. Very significant group and age effects were found for DA, HVA, 3MT, NE + E and 5HT. High HVA, 3MT, NE + E and 5HT levels were found in autistic and non-autistic children. The DA, HVA, 3MT, NE + E, 5HT and 5HIAA levels decreased significantly with age in the three groups. Significantly decreased levels of DA and HVA were observed in autistic children on haloperidol, compared with non-medicated autistic children. The results are discussed in relation to the hypothesis of a maturation defect of monoaminergic systems in autism.     

Free and conjugated 3, 4-dihydroxyphenylacetic acid and homovanillic acid in brain dopaminergic areas at basal state and after pipotiazine activation

Summary We have determined free and conjugated 3, 4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in discrete brain areas of rats.Conjugated HVA or DOPAC accounted for 22–38% of total acids in striatum, mesolimbic tissue or prefrontal cortex. Activation of dopamine (DA) metabolism by a single injection of pipotiazine palmitic ester (PPZ), a long-lasting neuroleptic, increased free acid levels (DOPAC and HVA) at either dose and conjugate levels after 32 or 50 mg/kg. 48 hours after PPZ-32 mg/kg, the observed increases of conjugates could exceed in some cases those of corresponding free acids.About half of total DOPAC and HVA were conjugated in hypothalamus, PPZ moderately increased free DOPAC (at 32 mg/kg) but did not elevate significantly the conjugated form.It is concluded that sulfation is an important pathway for DOPAC and HVA metabolism in brain and that the determination of both free and conjugated DOPAC or/and HVA may shed additional lights on regional DA metabolism and the effect of drags thereon.     

6-Hydroxydopamine lesions of dopaminergic A10 neurons. Long-term effects on the urinary excretion of free and conjugated catecholamines and their metabolites in the rat

Free and conjugated catecholamines (dopamine, noradrenaline, adrenaline) and their methoxylated and/or deaminated metabolites were studied in rat urine after the bilateral destruction of the A10 dopaminergic cell group. Two months after the lesion, dopamine (DA) loss reached 91% in the nucleus accumbens, and was greater than 80% in olfactory tubercles, lateral septum and frontal cortex. At the same time urinary conjugated dihydroxyphenylacetic acid (DOPAC) was decreased by 45% whilst homovanillic acid (HVA) was increased only in its sulfated form (+62%). In contrast, no changes were observed in the free and conjugated forms of urinary DA, 3-methoxytyramine noradrenaline, normetanephrine, adrenaline, vanylmandelic acid, 3-methoxy-4-hydroxyphenylglycol and in the free forms of DOPAC and HVA.The present report confirms and extends our previous findings on the relationships between central dopaminergic activity and urinary deaminated metabolites of DA in the rat. It emphasizes the interest of urinary assays which could provide in vivo information on CNS functions.     

Determination of conjugated monoamine metabolites in brain tissue

Summary Levels of free and conjugated monoamine metabolites were analysed in brain tissue of rat and man. In the rat the conjugates were mainly of the sulfate ester type. The levels of conjugated dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) constituted 40—50% of the total amount of the metabolites. 4-Hydroxy-3-methoxy-phenylglycol (HMPG) and 5-hydroxy-3-indoleacetic acid (5-HIAA) were present as conjugates in 90 and 10% of the total levels. Chlorpromazine treatment resulted in an elevation of both the free and the conjugated forms of the dopamine metabolites and HMPG. In a human caudate nucleus obtained at autopsy both DOPAC and HMPG were present in the free form and as sulfate and glucuronide conjugates. The major dopamine metabolite found in this human brain was HVA. This metabolite and 5-HIAA occurred predominantly as free metabolites.     

Differential effect of guanethidine on dopamine and norepinephrine pools in urine,heart and superior cervical ganglion in the rat

Summary The time-related changes of dopamine (DA) and norepinephrine (NE) pools were investigated in heart, superior cervical ganglion (SCG) and urine in rats treated chronically with guanethidine (50 mg/kg i.p. five days each week). The efficiency of sympathectomy was assessed by the great loss of NE in heart and superior cervical ganglion (SCG) (–96% and –76% respectively of control values on day 18) together with the ready reduction of NE and 3-methoxy-4-hydroxyphenylglycol (MHPG) in urine.The pattern of changes was quite different for DA, which was less readily affected and at a lesser extent than NE in heart and SCG thus suggesting the presence of norepinephrine-independent DA stores. Similarly the urinary excretion of free DA, free 3, 4-dihydroxyphenylacetic acid (DOPAC) and free homovanillic acid (HVA) was slightly decreased only from the 9th day, whereas urinary conjugated DA remained unaltered. These results indicate that the greatest portion of urine free and conjugated DA, free DOPAC and free HVA derives from peripheral pools located outside noradrenergic neurons. Alternatively, the time-course of DA sensitivity to guanethidine suggests that a portion of urine DA may originate from DA stored independently from NE in noradrenergic neurons.     

Apomorphine-haloperidol interactions: Different types of antagonism in cortical and subcortical brain regions

Apomorphine, a dopamine (DA) receptor stimulant induced a dose-dependent decrease in the content of the dopamine metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the olfactory tubercle and striatum of rats, but it was ineffective in the frontal cortex. Apomorphine also antagonized the haloperidol-induced accumulation of DOPAC and HVA in the olfactory tubercle and striatum, whereas in the frontal cortex it antagonized the effects of haloperidol on DOPAC but not on HVA. The total (free and conjugated) content of DA metabolites was measured in these experiments.     

Free and conjugated plasma homovanillic acid in schizophrenic patients

It has recently been suggested that the plasma level of homovanillic acid (HVA) may provide an index of central dopaminergic activity in humans. Clinical studies have shown that in schizophrenic patients, plasma HVA levels increase with the severity of psychopathology. However, these studies only considered the plasma free HVA fraction whereas investigations on conjugated HVA in humans are sparse and results remain controversial. The aim of this study was to measure both plasma free and conjugated HVA in healthy volunteers and drug-free schizophrenic patients. The mean values and the ranges of plasma free HVA in volunteers and patients were similar to those described in the literature. A substantial and significant increase in plasma free HVA was observed in schizophrenic patients compared with normal subjects. In contrast, plasma conjugated HVA was significatively decreased in schizophrenics. The plasma total HVA was nevertheless higher in schizophrenics compared with controls. No significant correlations were observed between plasma HVA levels and the clinical features of schizophrenic patients rated by various psychiatric scales. These findings suggest that there is an imbalance between plasma free and conjugated HVA in schizophrenic patients, who present an increase in total HVA when compared with controls. Paranoid schizophrenic patients, who present mainly positive symptoms, show the most marked plasma free/conjugated HVA imbalance.     

Concentration of monoamines and their metabolites in the cerebrospinal fluid from patients with senile dementia of the Alzheimer type and vascular dementia of the Binswanger type

Summary We measured the concentrations of total (conjugated and unconjugated) monoamines (dopamine, DA; norepinephrine, NE) and monoamine metabolites (homovanillic acid, HVA; 3-methoxy-4-hydroxyphenyleneglycol, MHPG; 5-hydroxyindoleacetic acid, 5-HIAA) in the cerebrospinal fluid (CSF), using HPLC-ECD in 11 patients with Alzheimer's disease (AD) or senile dementia of the Alzheimer type (SDAT), 17 patients with vascular dementia of the Binswanger type (VDBT), and 15 controls. In AD/SDAT, there was a significant decrease in the DA concentration and a significant increase in the MHPG concentration. The average NE concentration was not altered, but significantly increased with the progression of intellectual disability. There were no significant changes in HVA and 5-HIAA concentrations. Patients with VDBT showed a significant increase in the DA concentration and a significant decrease in HVA and 5-HIAA concentrations. The DA concentrations increased significantly with the progression of dementia and ventricular enlargement. These results indicate that the noradrenergic and dopaminergic system in particular are altered in AD/SDAT, while the dopaminergic and serotonergic systems are mainly involved in VDBT.     

Conjugated HVA increase in rat urine after insulin-induced hypoglycemia: Involvement of central dopaminergic structures but not of adrenal medulla

Summary To examine the possible contribution of Rat adrenal medulla to urinary DOPAC and HVA, we have studied these compounds in adrenals and urine under insulin-induced (5 IU/kg) hypoglycemic stimulation.In the urine samples collected over 16-hour-period following the intravenous insulin injection, there was a great increase in E, NE and their methoxylated derivatives MN and NMN, without change in DA, DOPAC, MHPG and free HVA excretion. In addition, there was a pronounced increase in urinary HVA conjugates (glucuronide and sulfate). Only very low amounts of DOPAC (10±2ng/gland; 0.05% of catechols) and no detectable amounts of HVA (<3 ng/gland) were found in adrenal glands, without no significant change two hours after insulin, thus suggesting that Rat adrenal glands are not meaningful sources for urinary HVA and DOPAC.Since free HVA and total MHPG excretion remained unchanged, HVA contribution from sympathetic neurons seems unlikely in our study.In contrast, highly increased levels of conjugated HVA-and at a lesser extent of conjugated DOPAC-have been found in the striatum, which appears to be the most likely source of urinary HVA increment. The dopaminergic activation following insulin affected too the hypothalamus but not the nucleus accumbens. The role of such central dopaminergic activation has been discussed in terms of feeding behavior.     

Variations of monoamines and their metabolites in the human brain putamen

The levels of the monoamines dopamine (DA), serotonin (5-HT) and norepinephrine (NE) and the monoaminergic metabolites 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) were measured with HPLC-ECD in 42 samples from human brain putamen. The influence of gender and of age was investigated and correlations between the monoamines were established. The DAergic system shows a significant difference between males and females, with females having lower DA and higher DOPAC levels and a higher DOPAC/DA ratio than males. No gender-related differences of 5-HT and its metabolites were observed, nor of NE. Three different age groups (group 1: 0–9.9 years; group 2: 10–59.9 years; group 3: 60 years and older) were defined according to previous studies on ontogenesis and senescence in human brain. An increase in 5-HT levels, decrease in 5-HIAA levels a d a decrease in the 5-HIAA/5-HT ratio were observed after the first decade of life. Changes in the DAergic system were seen in senescence, with decreasing DA levels and an increase in the HVA/DA ratio. DOPAC, HVA and the DOPAC/DA ratio are unaffected. NE is similar in all age groups. The analysis of the relation of the levels of the three monoamines proved a strong correlation between the DAergic and 5-HTergic systems. The nature of this relationship might have an impact on neuro-psychiatric disorders and brain function.     

Evolution of plasma homovanillic acid (HVA) in chronic schizophrenic patients treated with haloperidol

In a 4-week study of 14 drug-free schizophrenic patients (according to DSM-III-R), free and conjugated fractions of plasma homovanillic acid (pHVA) were repeatedly measured. Free HVA levels decreased during the first 2 h of haloperidol intake (P<0.03). Conjugated HVA levels slowly decreased during the following weeks (P<0.05), while free HVA levels remained stable. After 4 weeks, free HVA levels remained unchanged 2 h after morning haloperidol intake, but conjugated HVA levels tended to increase. In haloperidol responders, at baseline the free/total HVA ratio was significantly higher than that in non-responders (P<0.01). Tolerant patients, i.e. those whose post-treatment free HVA levels decreased below pre-treatment levels, were not found to respond better to haloperidol than non-tolerant patients. The balance between free and conjugated pHVA may be a better reflection of the action of haloperidol than free pHVA levels and it may be of prognostic value in terms of drug response.     

Frontal auditory-evoked potential augmenting-reducing and urinary homovanillic acid

Relationships between augmenting-reducing (Aug/Red) in auditory modality and dopaminergic metabolism were investigated in young adults with respect to sex. The slope values of evoked potential amplitude changes with increasing intensities were used to evaluate Aug/Red both at Cz and Fz for each of the five components: P1, N1, P2, P1N1, N1P2. The greatest slopes (Aug) were found in females. Individual differences in dopaminergic metabolism were estimated by assaying free and conjugated forms of homovanillic acid (HVA) in urines. HVA excretion rates were significantly more variable in males than in females. Relationships between Aug/Red and HVA levels were only found in males. The lower the Aug/Red slopes recorded at Fz site for the N1 component (weak augmenter or reducer responses), the higher the urinary HVA level and particularly the conjugated forms of HVA. These results are of interest for further applications in psychopathology.     

Post-mortem distribution of dopamine and homo-vanillic acid in human brain,variations related to age,and a review of the literature

Summary The post-mortem brain concentrations of dopamine (DA) and homo-vanillic acid (HVA) were determined in 16 parts of the brain from patients with no history of neurologic or psychiatric illness. Fifteen men and nine women, with a mean age of 61.0±18.7 years (range 23–92 years) were included. They had died from either ischaemic heart disease or cancer. In the post-mortem investigation several factors were controlled: age, time between death and autopsy, time between autopsy and chemical analysis and storage time (–20 °C).The DA concentrations in the different brain areas were found to be positively intercorrelated, especially those in the basal ganglia, hippocampus and the mesencephalon. The HVA concentrations measured in various cortical structures were also positively intercorrelated. In several regions of the brain there was a significant inverse correlation between the DA and HVA concentrations.The DA and HVA concentrations did not differ according to sex, but age had a marked influence on the DA concentration. Significant decrease with age was observed in the nucleus caudatus, globus pallidus, mesencephalon, hippocampus and in the cortex gyrus hippocampus. These findings are discussed in relation to the effect of aging neurons.A review of human post-mortem investigations on DA and HVA concentrations is also presented.     

Distribution of norepinephrine, epinephrine, dopamine, serotonin, 3,4-dihydroxyphenylacetic acid, homovanillic acid and 5-hydroxyindole-3-acetic acid in dog brain

The distribution and endogenous concentrations of norepinephrine, epinephrine, dopamine, serotonin, 3,4-dihydroxyphenylacetic acid, homovanillic acid and 5-hydroxyindole-3-acetic acid were determined in the brains of adult dogs. Norepinephrine and epinephrine were localized primarily in 'central core' areas in brain stem and hypothalamus. Dopamine (DA) and its major metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acids (HVA), were localized primarily in basal ganglia with relatively high concentrations also found in amygdala, septum and substantia nigra. HVA was also found in relatively high concentrations in areas where DA concentrations was very low. Serotonin and 5-hydroxyindole-3-acetic acid levels were highest in brain stem, hypothalamus, globus pallidus and nucleus accumbens. Epinephrine levels were higher than in previously studied species, at times as much as 25-30% of norepinephrine and frequently greater than dopamine in brain stem and hypothalamus. Using the ratios 5-hydroxyindole-3-acetic acid/serotonin and homovanillic acid/dopamine as indicators of serotonin and dopamine turnover and utilization, both putative transmitters were found to be generally more highly utilized in areas of lower concentration, especially in brain stem and cortex. Catecholamines were found to be unconjugated in dog brain. DOPAC and HVA were found to exist primarily in the unconjugated form. DOPAC was found to be slightly conjugated in most areas while 10-20% of HVA was present in the conjugated form in most cases.     

Monoaminergic and cholinergic synaptic markers in the nucleus basalis of Meynert (nbM): normal age-related changes and the effect of heart disease and Alzheimer's disease.

Neurotransmitter markers for acetylcholine, serotonin (5-HT), and dopamine (DA) were measured in autopsied human nucleus basalis of Meynert (nbM) from nondemented individuals without heart disease (non-HD) (age range, 4-84 years; n = 77), nondemented individuals with heart disease (HD) (age range, 57-92 years; n = 23), and individuals with Alzheimer's disease (AD) (age range, 59-92 years; n = 22). No significant differences in any chemical marker were found between age-matched HD and non-HD individuals. The activities of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE), and [3H]spiperone binding were regionally distributed within the nbM in control (non-HD) subjects less than 54 years of age. The activity of AChE, 5-[3H]HT binding, and the content of homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), and 5-HT were regionally distributed in the nbM in non-HD, HD, and AD subjects more than 54 years of age. The binding of [3H]spiperone was regionally distributed in the nbM in HD and AD subjects more than 54 years of age, only. Activity of ChAT and AChE, content of 5-HT, 5-HIAA, and DA, binding of 5-[3H]HT, and the turnover number for DA (ratio of HVA/DA) all decreased with increasing age in the non-HD control population. The content of HVA, binding of [3H]spiperone, and the turnover number for 5-HT (ratio of 5-HIAA/5-HT) did not change with increasing age. Significant reductions in ChAT and AChE activities were found in AD nbM compared with postmortem interval- and age-matched HD and non-HD individuals. The reduction of 5-HT and 5-HIAA content and [3H]spiperone binding in individuals with AD of all ages suggests a loss of functional serotonergic innervation of the nbM. Dopaminergic synaptic markers were less affected in AD nbM, although turnover numbers for both DA and 5-HT were increased in AD. Receptor upregulation in response to presynaptic deficits did not occur for DA or 5-HT.     

In vivo analysis of dopamine and its metabolites in the caudate nucleus during euthermia and hibernation

Golden-mantled ground squirrels (Citellus lateralis) were chronically implanted with a unilateral push-pull cannula in the caudate nucleus. Perfusates obtained in these unanesthetized, unrestrained animals during the euthermic (non-hibernating) and hibernating states were analyzed for dopamine (DA) and its metabolites (homovanillic acid (HVA), 3,4-dihydroxyphenylacetic acid (DOPAC), and 3-methoxy-4-hydroxyphenethanol (MOPET) using high performance liquid chromatography with electrochemical detection. The data revealed clear differences in the performance of the caudate DA system in the two states. During the euthermic state, DA metabolism was indicative of a constant and high turnover rate. Free DA was not detectable in the majority of samples, HVA was detected at consistently high levels, and DOPAC and conjugated DA were present at low levels. By contrast, DA metabolism was sharply altered during hibernation. Free DA was present at high concentrations and HVA concentrations were low. DOPAC was not detected in any sample whereas MOPET was present in all samples. Conjugated DA was present at high concentrations during the second half of the hibernation bout. The shift in the post-release disposition of DA could enhance the stability of DA receptors (i.e. prevent supersensitivity) during the prolonged periods of reduced neural activity typical of hibernation.     

Urinary dopamine metabolites as indicators of the responsiveness to fenfluramine treatment in children with autistic behavior

Modifications in serotonin and dopamine metabolism were evaluated in 13 children with autistic behavior and related to their responsiveness to fenfluramine treatment. A double-blind medication-placebo crossover design was used. Each patient received 1.5 mg/kg fenfluramine daily for 3 months followed and preceded by placebo for 1 month. Clinical improvement was observed in 6 children (responders). It included reduction of behavioral symptoms such as motor activity, anxiety, mood disturbances, and distractibility. Modifications of serotonin (5-HT), dopamine (DA), and DA metabolites [homovanillic acid (HVA) and dihydroxyphenylacetic acid (DOPAC)] were assessed at urinary levels. Responders and nonresponders showed a significant decrease of urinary 5-HT levels on fenfluramine. The main differences between the two groups of subjects were found with HVA, the major metabolite of DA. Fenfluramine significantly increased HVA levels in responders whereas no significant modification was found in nonresponders. Moreover the initial level of HVA (lower in responders) significantly differentiated the two groups. These results suggest that the clinical response to fenfluramine could be related to the dopaminergic action of this drug and that urinary DA metabolite levels could be considered as indicators of the responsiveness to fenfluramine treatment in children with autistic behavior.     

Human brain dopamine metabolism in levodopa-induced dyskinesia and wearing-off

The objective of this study was to identify dopamine (DA) metabolism pattern in Lewy body Parkinson's disease (PD) patients with dyskinesia (Dysk) only, with wearing-off (WO) only, or no motor complications (NMC) induced by levodopa (LD). DA, homovanillic acid (HVA), 3,4-dihydroxyphenylacetic acid (DOPAC), and 3-methoxytyramine (3-MT) were measured individual basal ganglia nuclei of nine PD patients who received LD for 6-18 years. Three patients had only Dysk, three only WO, and three had neither Dysk nor WO. Biochemical measurements in PD brains were compared with four non-neurological control brains from individuals matched for age and post-mortem retrieval time. DA levels in the PD were reduced in the caudate by 87% and putamen by 99%. In the caudates, the HVA/DA molar ratio as an index of DA metabolism was similar in the WO and the Dysk patients. However, in the putamen, the ratio of HVA/DA was significantly higher in the WO compared with the Dysk (p = 0.03)and the NMC (p = 0.04) groups of patients. In the putamen, the DOPAC levels were higher in the WO cases while in the Dysk cases, 3-MT levels were higher. The results suggest that in the WO only cases, the putaminal DA was in large measure metabolized intraneuronally while the DA metabolism in our Dysk only patients was mainly extraneuronal. We conclude that the magnitude and the site (intra vs. extraneuronal) of the synaptic DA metabolism in the putamen plays a significant role in LD-induced Dysk and WO.     

Cerebrospinal fluid (CSF) and brain monoamine metabolites in the developing rat pup

Concentrations of the neurotransmitters, serotonin (5-HT), dopamine (DA), and norepinephrine (NE) were measured in the developing rat brain at 12, 19, 26 and 42 days of age. The amino acid precursors, tryptophan (TRP) and tyrosine (TYR) were measured along with the 5-HT and DA metabolites, 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA), in brain and cerebrospinal fluid (CSF) at the above ages. This first report of CSF HVA levels in the developing rat shows that it, like 5-HIAA, declines with age. In contrast, the ontogeny of the compounds in brain are dissimilar, with 5-HIAA remaining relatively constant with age while HVA declines markedly. Possible reasons for the differences and similarities in the ontogeny of 5-HIAA and HVA levels in brain and CSF are discussed. The persistence of the ontogenetic pattern for the neurotransmitters and acid metabolites after central DA depletion is also reported.     

Free and conjugated amino acids in human CSF: Influence of age and sex

An extended baseline characterization of amino acids (AAs) and related amino compounds in CSF is reported. Thirty-one amino compounds were measured in deproteinized CSF before and after acid hydrolysis using a triple-column HPLC/fluorometric analyzer. CSF specimens were collected under strictly controlled conditions from neurologically normal myelogram patients and carefully pooled with regard to subject age and sex. Consideration was given to factors which may produce artifactual alterations in AA levels during CSF collection, storage and handling. Conjugated AAs were determined as the difference between levels of free AAs (measured in CSF prior to hydrolysis) and total AAs (measured in hydrolyzed CSF) and are taken as an index of total CSF peptide AAs. Results documented conjugated forms of all non-acid-labile CSF AAs except citrulline and ethanolamine. In general, ratios of conjugated to free AAs were relatively low, however for the neurotransmitter AAs aspartate, glutamate, glycine and GABA as well as for beta-alanine hydrolysis produced marked increases indicating that these compounds are present predominantly in bound form in CSF. Results also revealed the significant influence of both age and sex on levels of a number of CSF free and conjugated AAs. Compared to younger individuals (those less than 40 years of age), older individuals exhibited significantly higher levels of free aspartate, glycine, alpha-aminobutyric acid, valine, isoleucine, leucine, phenylalanine and 3-methylhistidine as well as significantly lower levels of free phosphoethanolamine, serine, GABA, homocarnosine, conjugated GABA and conjugated beta-alanine. Additionally, significantly higher levels of free tyrosine, ethanolamine, arginine and conjugated aspartate were documented in males compared to females.(ABSTRACT TRUNCATED AT 250 WORDS)