Rapid, concurrent analysis of dopamine, 5-hydroxytryptamine, their precursors and metabolites utilizing high performance liquid chromatography with electrochemical detection: analysis of brain tissue and cerebrospinal fluid

Simulated Microgravity Subtlety Changes Monoamine Function across the Rat Brain

Microgravity, one of the conditions faced by astronauts during spaceflights, triggers brain adaptive responses that could have noxious consequences on behaviors. Although monoaminergic systems, which include noradrenaline (NA), dopamine (DA), and serotonin (5-HT), are widespread neuromodulatory systems involved in adaptive behaviors, the influence of microgravity on these systems is poorly documented. Using a model of simulated microgravity (SMG) during a short period in Long Evans male rats, we studied the distribution of monoamines in thirty brain regions belonging to vegetative, mood, motor, and cognitive networks. SMG modified NA and/or DA tissue contents along some brain regions belonging to the vestibular/motor systems (inferior olive, red nucleus, cerebellum, somatosensorily cortex, substantia nigra, and shell of the nucleus accumbens). DA and 5-HT contents were reduced in the prelimbic cortex, the only brain area exhibiting changes for 5-HT content. However, the number of correlations of one index of the 5-HT metabolism (ratio of metabolite and 5-HT) alone or in interaction with the DA metabolism was dramatically increased between brain regions. It is suggested that SMG, by mobilizing vestibular/motor systems, promotes in these systems early, restricted changes of NA and DA functions that are associated with a high reorganization of monoaminergic systems, notably 5-HT.

Acute low-level formaldehyde behavioural and neurochemical toxicity in the rat

The purpose of the present study was to determine the effects of low-level formaldehyde exposure upon behavior and neurochemistry in the male rat. Rats were exposed to either air or formaldehyde vapor (5, 10 or 20 parts per million) for 3 hours on 2 consecutive days during which behavioral observations were made. Following the second exposure session the rats were sacrificed and their brains analyzed for norepinephrine, dopamine, 5-hydroxytryptamine and their major metabolites. Formaldehyde exposure resulted in decreased motor activity and neurochemical changes in dopamine and 5-hydroxytryptamine neurons.

Neurotoxic effects in adult mice neonatally exposed to 3,3'4,4'5-pentachlorobiphenyl or 2,3,3'4,4'-pentachlorobiphenyl. Changes in brain nicotinic receptors and behaviour

The objective of the present study was to investigate whether neonatal exposure to single PCB congeners 3,3',4,4',5-pentachlorobiphenyl (IUPAC 126) (co-planar) and 2,3,3',4,4'-pentachlorobiphenyl (IUPAC 105) (mono-ortho `co-planar like') when given as one single dose (0.14-14 μmol/kg body weight per os) to 10 day old male NMRI mice could induce neurotoxic effects in the adult animal, as earlier seen for some ortho-substituted PCBs. Furthermore, to ascertain whether behavioural aberrations, both in spontaneous behaviour and in learning and memory function, were followed by changes in the cholinergic and/or the dopaminergic system, and whether behavioural changes could worsen with age. It was found that neonatal exposure to 3,3',4,4',5-pentachlorobiphenyl can induce persistent aberrations in spontaneous behaviour and that this derangement can grow worse with age. Furthermore, this exposure affected also learning and memory functions in the adult animal and in the animals showing this deficit, the cholinergic nicotinic receptors in the hippocampus were affected. Exposure to 2,3,3',4,4'-pentachlorobiphenyl, at the same dose or higher, did not cause any significant change in the investigated behavioural variables, spontaneous and swim-maze behaviour.

Developmental neurotoxicity of four ortho-substituted polychlorinated biphenyls in the neonatal mouse

The objective of the present study was to investigate whether neonatal exposure to single PCB (polychlorinated biphenyl) congeners 2,4,4'-trichlorobiphenyl (IUPAC 28), 2,2',5,5'-tetrachlorobiphenyl (IUPAC 52), 2,3',4,4',5-pentachlorobiphenyl (IUPAC 118) and 2,3,3',4,4',5-hexachlorobiphenyl (IUPAC 156) when given as one single dose (0.7-14 μmol/kg body weight per os) to 10-day-old male NMRI mice could induce persistent neurotoxic effects in the adult animal. Furthermore, to ascertain whether behavioural aberrations, both in spontaneous behaviour and in learning and memory function, were followed by changes in the cholinergic and/or the dopaminergic system. It was found that neonatal exposure to lightly chlorinated ortho-substituted PCBs, 2,4,4'-tri- and 2,2',5,5'-tetrachlorobiphenyls, can induce persistent aberrations in spontaneous behaviour. Neonatal exposure to 2,2',5,5'-tetrachlorobiphenyl also affected learning and memory functions in the adult animal. In the animals showing a deficit in memory and learning function, the cholinergic nicotinic receptors in the cerebral cortex were affected. Exposure to 2,3',4,4',5-penta- and 2,3,3',4,4',5-hexachlorobiphenyl, mono-ortho congeners ('co-planar-like'), in the same dose range did not cause any significant change in the investigated behavioural variables, spontaneous and swim-maze behaviour.

Simultaneous changes in striatal dopamine, serotonin, and metabolites after withdrawal seizures in rats from dependence on alcohol

Ethanol dependence was achieved in male, Long-Evans rats after 8 days on a balanced liquid diet that supplied 4.5% ethanol. After 1-h access to a solution of 10% ethanol (95%)/5% sucrose, the rats were deprived of food, water, and ethanol for 9 h. Following 30-s key jingling, about 80% of the animals exposed to ethanol experienced tonic-clonic seizures. Neurochemical analyses of striatal tissues revealed a significant (p < 0.05) increase in dopamine (DA) and a significant decrease in serotonin (5-HT) in the ethanol-exposed rats that had seizures compared to control rats. Homovanillic acid concentrations of the ethanol-treated rats with seizures were significantly higher than the levels found in ethanol-treated animals that had experienced no seizures. Daily average ethanol intake of the rats that had seizures vs. those that did not was almost the same at 16 g/kg/day. The findings indicate that rats experiencing ethanol withdrawal-induced seizures manifest opposite alterations in dopaminergic and serotoninergic activity compared to controls. The present results do not reveal if the striatal changes are caused by ethanol rather than by the seizures.

Disruptive influence of norepinephrine depletion on sensory preconditioning, but not first-order conditioning, in preweanling rats

Learning and memory processes are known to be influenced by the action of norepinephrine (NE). The present study evaluated the influence of neonatal administration of the NE neurotoxin DSP4 on sensory preconditioning (SPC) in 16- and 28-day-old rats. Rats were subcutaneously administered 50 mg/kg DSP4 or saline within 24 h after birth and tested at 16 or 28 days in two experiments. The results from Experiment 1 indicated that nondepleted 16-day-old rats exhibited strong SPC, whereas this conditioning was disrupted by neonatal administration of DSP4. No SPC was seen in either neonatal treatment group at 28 days of age, confirming previous reports of an ontogenetic decline in SPC. In Experiment 2, no effects of DSP4 were observed on first-order conditioning at either age. The brains of representative subjects were separated into forebrain, cerebellum, and brain stem samples and were analyzed to determine the extent of NE depletion. This analysis showed that DSP4 produced a marked reduction in NE concentration in the forebrain, but not in the cerebellum or brain stem. The results of this study suggest a role for forebrain NE in SPC in preweanling rats. This modulatory noradrenergic influence appears to be exerted on the formation of associations between two relatively neutral stimuli during the preexposure phase, given the absence of an effect of DSP4 on primary conditioning.

A sex comparison of serotonin immunoreactivity and content in the ferret preoptic area/anterior hypothalamus

Previous studies with rats raised the possibility that sexually dimorphic features of the medial preoptic area/anterior hypothalamus (POA/AH) may result, in part, from a sex difference in the serotonergic innervation of this region. We asked whether a similar phenomenon may occur in a carnivore, the ferret. A sexually dimorphic male nucleus of the dorsal POA/AH (Mn-POA/AH) has previously been characterized in Nissl-stained sections of the male ferret forebrain; this nucleus is absent in females. A nondimorphic ventral nucleus of the POA/AH is found in both sexes. In the present study numerous serotonin (5-HT) immunoreactive (ir) fibers were observed in the dorsal POA/AH of gonadectomized adult ferrets of both sexes. By contrast, in both sexes the ventral nucleus of the POA/AH had many fewer 5-HTir fibers. A similar difference in the distribution of immunoreactivity between dorsal and ventral POA/AH was observed for tyrosine hydroxylase (TH) localized in cell bodies and in nerve fibers and for H222ir estrogen receptors localized in cell nuclei. Likewise, in both sexes the content of 5-HT and dopamine (DA), measured by high pressure liquid chromatography with electrochemical detection, were significantly higher in the dorsal than the ventral POA/AH, thereby corroborating observed regional differences in 5-HTir and THir fibers, respectively. The present findings provide no support for the notion that sexually dimorphic cytoarchitectonic features of the dorsal POA/AH in ferrets are associated with a sex difference in the serotonergic innervation of this region.

Effects of acute dopamine depletion on responsiveness to D1 and D2 receptor agonists in infant and weanling rat pups

The behavioral responses to separate and combined administration of the D1 agonist SKF-38393 and the D2 agonist quinpirole following acute dopamine (DA) depletion via alpha-methyl-p-tyrosine (AMPT) or AMPT/reserpine were examined in infant (10-day-old) and weanling (21-day-old) rat pups. At both ages, AMPT pretreatment generally had little impact on D1- or D2-agonist-induced responding, whereas the greater DA depletion observed following AMPT/reserpine pretreatment was generally associated with suppression of both D1 and D2-agonist-typical responding. Thus, whereas in adult animals some degree of D1 receptor activation by endogenous dopamine appears to be necessary for D2 responding but not vice versa (e.g. White et al. 1988), in young animals there appears to be a reciprocal co-dependence of these two receptor subtypes, with extensive DA depletion suppressing responding to both agonists when administered separately. At 10 days of age, some D1 and D2 agonist-induced behaviors that were previously blocked by AMPT/reserpine were reinstated following combined administration of both agonists. In contrast, no clear evidence for reinstatement was seen following administration of the combined agonists to AMPT/reserpine-pretreated weanlings, perhaps due to the induction of potential competing behaviors. Whereas DA depletion blocked many D1- and D2-induced behaviors, such depletion conversely promoted the expression in agonist-treated animals of a number of behaviors that were not normally induced by the agonists in non-depleted animals. These behaviors typically involved an oral component and included grooming and mouthing following SKF-38393 in depleted 10-day-old pups, mouthing following administration of either agonist to depleted weanlings, and probing and intense self-mutilation (forepaw and tongue biting) following the combined agonists in depleted weanlings. This rapid induction of potentiated agonist responsiveness following acute DA depletion early in life may have significant implications with regard to animal models for the developmental disorder of Lesch-Nyhan syndrome.

Levels of pros-methylimidazoleacetic acid: correlation with severity of Parkinson's disease in CSF of patients and with the depletion of striatal dopamine and its metabolites in MPTP-treated mice

The cerebrospinal fluid (CSF) levels of pros-methylimidazoleacetic acid (p-MIAA) in thirteen medication-free patients with mild to moderate Parkinson's disease were highly correlated (Spearman's rho = 0.749, p less than 0.005) with the severity of signs of the disease as scored on the Columbia University Rating Scale. Levels of p-MIAA in males (n = 8) and females (n = 5) were each significantly correlated with scores of severity (rho = 0.78, p less than 0.05 and rho = 1.0, p less than 0.05, respectively). In C57BL/6 mice treated with 1-methyl-4-phenyl-1,2,3,6-tetra-hydropyridine (MPTP), levels of p-MIAA were significantly correlated with the depleted levels of dopamine (r = 0.85, p less than 0.01), homovanillic acid (r = 0.79, p less than 0.02), 3,4-dihydroxyphenylacetic acid (r = 0.84, p less than 0.01) and norepinephrine (r = 0.91, p less than 0.002) in striatum, but not in cortex of the same mice. No such correlations were observed in either striatum or cortex of saline-treated control mice. Mean levels of p-MIAA in CSF did not differ significantly between patients and age-matched controls; and mean levels of p-MIAA in striatum did not differ between MPTP-treated mice and controls. The simplest hypothesis to account for these strong correlations in the absence of differences in mean levels of p-MIAA is that accumulation of p-MIAA [or process(es) that govern its accumulation] influences a failing nigrostriatal system. It is also possible (in analogy with findings in other diseases and with other drugs) that measurements of the putative metabolite(s) of p-MIAA may distinguish the patients and the MPTP-treated mice from their respective controls. Elucidation of the processes that regulate formation and disposition of p-MIAA in brain and information on the neural effects of p-MIAA, its precursors and its putative metabolites may yield insight into factors that regulate the progression of Parkinson's disease, and may shed additional light on the cause(s) of this disease.

Analysis of cat retina for dopamine, dihydroxyphenylacetic acid, 3-methoxytyramine and homovanillic acid

Twenty retinas from 10 cats were evaluated for dopamine (DA) and its metabolites dihydroxyphenylacetic acid (DOPAC), 3-methoxytyramine (3-MT) and homovanillic acid (HVA) by high pressure liquid chromatography and electrochemical detection. Dopamine was present in all 20 retinas at a mean concentration of 3.00 +/- 0.54 ng/mg protein. Dihydroxyphenylacetic acid, 3-MT and HVA were detected in 16, 14 and 9 retinas respectively. In retinas in which these metabolites were detectable, they were present in the following mean concentrations: DOPAC, 1.07 +/- 0.21 ng/mg protein; 3-MT, 3.44 +/- 0.97 ng/mg protein and HVA, 4.54 +/- 1.05 ng/mg protein. Significantly higher concentrations of 3-MT (p = 0.0108, paired t test) and HVA (p = 0.0166, paired t test) than DOPAC were present in cat retina. Linear correlation analysis between DA and its metabolites indicated that the 3-MT and DOPAC concentrations correlated well with each other and with the amount of DA in cat retina. The concentrations of the end product metabolite, HVA, had poor correlations with the concentrations of 3-MT, DOPAC or DA. These data indicated that once DA is released in cat retina it can be metabolized to 3-MT, DOPAC and HVA.

Analysis of equine cisterna magna cerebrospinal fluid for the presence of some monoamine neurotransmitters and transmitter metabolites

Small volumes (0.05 ml) of cisterna magna cerebrospinal fluid (CSF) from 23 neurologically normal horses were analysed for the monoamine neurotransmitters dopamine, norepinephrine, epinephrine, serotonin and their metabolites using high pressure liquid chromatography and electrochemical detection. Two metabolites, homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) were present in all CSF samples. The deaminated and methylated metabolite of dopamine, HVA, was present at a mean concentration of 42.33 +/- 3.14 ng/ml of CSF. The deaminated metabolite of serotonin, 5-HIAA, was present at a mean concentration of 45.52 +/- 3.65 ng/ml of CSF. A positive correlation was found between the CSF concentrations of HVA and 5-HIAA (r = 0.72, p = 0.0003). The mean ratio of HVA to 5-HIAA concentrations was 1.07 +/- 0.05. The ratios of HVA to 5-HIAA concentrations were found to be more indicative of the serotonergic metabolite 5-HIAA (r = -0.62, p = 0.0016) than the dopaminergic metabolite HVA (r = 0.11, p = 0.60). There was a stronger relationship between the concentrations of 5-HIAA and the ratios of HVA to 5-HIAA in male CSF (r = -0.85, p = 0.0006) than in female CSF (r = -0.54, p = 0.01). Concentrations of CSF neurotransmitter metabolites were evaluated in horses grouped by age (0-4, 5-9 and 10-13 years). The youngest group of horses had a significantly (p = 0.003) greater CSF concentration of HVA than of 5-HIAA. The 10-13-year-old horses had a significantly (p = 0.02) lower mean CSF HVA concentration than the 0-4-year-old horses. No age-related differences in CSF 5-HIAA concentrations were detected.

Dietary pyridoxine interaction with tryptophan or histidine on brain serotonin and histamine metabolism

We studied the metabolic effects of high dietary intakes of pyridoxine and of the substrate-cofactor interaction between dietary histidine or tryptophan and pyridoxine in rat brain. In the substrate-cofactor interaction study, histamine and serotonin levels were determined in rats fed elevated or requirement levels of substrate (histidine: 0.3% and 0.8%, tryptophan: 0.15% and 0.6%) and excess or requirement levels of pyridoxine HCl (7 mg vs. 3,000 mg/kg). Excess pyridoxine intake caused a differential effect on brain histamine concentration--inhibitory with the requirement level of histidine (-29%), and stimulatory (+21%) with the elevated level of histidine. When dietary tryptophan was fed at the requirement level, excess pyridoxine caused essentially no changes in hypothalamic serotonin and 5HIAA (-2%, -2%). With elevated tryptophan intake, excess pyridoxine significantly increased serotonin and 5HIAA (+32%, +20%) in the hypothalamus. These results indicate a clear interaction between substrate and coenzyme precursor which influences brain metabolism of histamine and serotonin.

The effects of L-tryptophan on haloperidol-induced movement disorder in the rat

An animal model of haloperidol-induced tardive dyskinesia was studied in relation to the dietary manipulation of tryptophan and its effect on the movement disorder. This study showed a significant negative behavioral response to the neuroleptic drug, haloperidol. Increased dietary tryptophan (1.0 vs. 0.3%) significantly reduced the frequency of drug-induced head movements. Brain serotonin levels were elevated by the drug treatment. Brain serotonin levels correlated significantly with the behavioral response. Contrary to expectation, brain dopamine levels did not correlate with the behavioral response. These findings suggest a possible serotonergic involvement in neuroleptic-induced tardive dyskinesia and an amelioration of the disorder through tryptophan supplementation.

Biochemical and behavioural indices of striatal dopaminergic activity after 6-methyltetrahydropterin

The biochemical effects of 6-methyltetrahydropterin (6-MPH4), a synthetic analogue of tetrahydrobiopterin (BH4), the hydroxylase cofactor, were investigated on striatal dopaminergic neurons in the rat. Although a single parenteral dose of 6-MPH4 (18 or 54 mg/kg) did not significantly increase the content of dopamine (DA) or its acidic metabolites, L-didrohyphenylanine (L-DOPA) accumulation after decarboxylase inhibition was evident in rats receiving 54 mg/kg of 6-MPH4. On the other hand, 6-MPH4 (18 mg/kg) potentiated the reserpine-induced DA metabolism as demonstrated by increased HVA levels. In a behavioural test, 6-MPH4 partially prevented haloperidol-induced catalepsy. BH4 concentrations could thus be subsaturating with respect to tyrosine hydroxylase (TH), particularly when the enzyme activity is stimulated and the results suggest that cofactor supply may have pharmacological significance.

Rapid and sensitive method for measuring norepinephrine, dopamine, 5-hydroxytryptamine and their major metabolites in rat brain by high-performance liquid chromatography. Differential effect of probenecid, haloperidol and yohimbine on the concentrations of biogenic amines and metabolites in various regions of rat brain

A rapid and sensitive method has been developed for the simultaneous determination of norepinephrine, dopamine, 5-hydroxytryptamine and their respectively metabolites 3-methoxy-4-hydroxyphenylglycol, homovanillic acid, 3,4-dihydroxyphenylacetic acid, and 5-hydroxyindoleacetic acid in discrete brain regions of rats. The supernatants of tissue homogenates were injected directly into a reversed-phase liquid chromatography system, coupled with electrochemical detection. Each of these compounds gave a linear response over the range 5.5-200 ng/ml cerebellar homogenate (0.11-4.0 ng on column). Analytical recoveries of these compounds, added to the homogenate, were essentially complete when compared with standards dissolved in perchloric acid. The average between-assay coefficients of variation for all these compounds were lower than 6.9% over the range 5.5-200 ng/ml. The within-assay coefficients of variation were lower than 9.7%, measured at 5.5 or 23.6 ng/ml. With the present test parameters and mobile phase conditions, all compounds were readily oxidized at 0.8 V vs. a Ag/AgCl reference electrode. The method was applied to an analysis of the differential activity of biogenic amines in the rat striatum, hypothalamus, and hippocampus, produced by probenecid, haloperidol and yohimbine.

Simultaneous determination of biogenic amines and morphine in discrete rat brain regions by high-performance liquid chromatography with electrochemical detection

A simple and sensitive method has been developed for the simultaneous determination of norepinephrine, epinephrine, dopamine, 5-hydroxytryptamine, 5-hydroxyindoleacetic acid, and morphine in discrete rat brain regions by reversed-phase high-performance liquid chromatography with electrochemical detection. Perchloric acid extracts of the tissue were directly injected into the chromatographic system. Each of these compounds gave a linear response over the range of 20-160 ng/ml cerebellar homogenate (0.4-3.2 ng on column). Recoveries of these compounds, added to the homogenates, were complete when compared with standards dissolved in perchloric acid. The average between-run coefficients of variation for all these compounds were lower than 7.4% over the range of 20-160 ng/ml, and the within-run coefficients of variation at 20 ng/ml were lower than 8.7%. The present method has been applied to a study of the effects of intraperitoneal administration of morphine on biogenic amines in several discrete rat brain regions.

Investigation of dopamine content, synthesis, and release in the rabbit retina in vitro: I. Effects of dopamine precursors, reserpine, amphetamine, and L-DOPA decarboxylase and monoamine oxidase inhibitors

The basal catecholamine content of rabbit retina was determined by liquid chromatography with electrochemical detection (LC-EC) and 3,4-dihydroxyphenylethylamine (dopamine, DA) found to be the major catecholamine. The immediate DA precursor, 3,4-dihydroxyphenylalanine (L-DOPA), and the metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC), were also detected at about 2.8% and 17% of DA levels, respectively. When added exogenously, L-tyrosine did not increase the rate of DA synthesis over the basal level. In contrast, exogenous L-DOPA led to a 3.5-fold increase in DA, and to a 20-fold increase in DOPAC content. The monoamine oxidase inhibitors pargyline and (-)-deprenyl differentially affected the degradation of DA, since 100 microM pargyline was apparently more effective than 100 microM (-)-deprenyl. Reserpine and (+/-)-amphetamine each induced a Ca2+-independent decrease of DA stores. The separate actions of reserpine and (+/-)-amphetamine in lowering tissue DA levels were additive, suggesting two separate pools of DA available for release from presynaptic stores. The present study demonstrates that the LC-EC technique may be used to investigate the modulation of the synthesis and release of retinal DA in vitro, without the prior uptake of radiolabelled transmitter.

Analysis by HPLC-EC of metabolites of monoamines in fetal and postnatal rat brain

High performance liquid chromatography with electrochemical detection (HPLC-EC) was adapted for the analysis of metabolites of monoamines (MA) in the developing brain of the rat. 3-Methoxy-4-hydroxy-phenyl-ethylene glycol (MOPEG), dihydroxy phenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxy-3-indoleacetic acid (5-HIAA) were found in significant amounts in forebrain of the foetal rat from gestational day (GD) 17. The development pattern of the four metabolites was essentially similar in male and female animals. Except for transient fluctuations at around birth, concentrations of metabolites increased gradually throughout late gestation and early postnatal life. In late gestation and at birth the absolute amounts were small, while the concentrations were comparable to adult levels.

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

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 drugs thereon.

Different patterns of CSF neurotransmitter metabolism in patients with left or right hemispheric stroke

In 30 ischemic stroke patients, divided into 2 groups depending on the side of their hemispheric cerebral lesion, the authors evaluated the levels of CSF homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA). The changes of these metabolites in CSF samples collected 3, 14 and 25 days after stroke have been correlated to the clinical course. In both groups, which were similar in respect to the localization of the infarcted area and to the volume of the lesion, the levels of HVA and 5-HIAA increased in the first 2-3 days and gradually declined to normal values in the following 3 weeks, in parallel with the regression of neurological deficits. The increase of HVA and 5-HIAA was statistically significant only in left hemisphere-injured patients. A linear regression analysis between the clinical score values and the CSF levels of the two metabolites at different time-points of observation revealed a significant correlation only for the HVA in the left-lesioned patients.

Flunarizine limits hypoxia-ischemia induced morphologic injury in immature rat brain

We examined the impact of pre-treatment with the calcium antagonist flunarizine on the development of hypoxic-ischemic brain injury in the immature rat. Unilateral carotid artery ligation and subsequent exposure to 2 hours of 8% oxygen in 7-day-old rats was used as a model for perinatal hypoxic-ischemic encephalopathy. This procedure leads to atrophy in the cerebral hemisphere ipsilateral to carotid occlusion, with prominent foci of neuronal infarction in the caudate-putamen (striatum). The morphologic injury develops after 1 1/2 hours of hypoxia; and there is an equivalent time threshold for duration of hypoxic exposure needed to acutely stimulate dopamine release in the ipsilateral striatum. Parenteral administration of 30 mg/kg of flunarizine before hypoxic exposure limited both the release of dopamine acutely and the extent of morphologic damage observed two weeks after the insult. Oral administration of 30 mg/kg of flunarizine in a different vehicle prevented morphologic damage but had no effect on stimulated dopamine release. The drug vehicle for the parenteral preparation also prevented tissue injury, but to a lesser degree than flunarizine. However the parenteral vehicle was equipotent with parenteral flunarizine in limiting acute stimulation of dopamine release. The results demonstrate that flunarizine has potent neuroprotective properties against morphologic brain injury from hypoxia-ischemia, acting by a mechanism which is independent of effects on dopamine release.

Effects of acute and chronic bupropion on locomotor activity and dopaminergic neurons

Acute administration of bupropion (10 or 30 mg/kg) to rats increased locomotor activity in a dose-related manner. The highest dose increased the dopamine (DA) concentration while both doses reduced the concentration of dihydroxyphenylacetic acid (DOPAC) in the striatum. The enhancement of locomotor activity and the decrease of striatal DOPAC concentrations were increased with chronic administration (up to 40 days) of bupropion. The rate of DA synthesis in the striatum was increased by the acute administration of d-amphetamine but was not altered by acute or chronic administration of bupropion.

Evidence for species differences between rats and gerbils in striatal dopamine content and dopamine metabolism

High-performance liquid chromatography revealed significantly higher striatal concentrations of dopamine and homovanillic acid (HVA) in 9 male Mongolian gerbils than in 6 male Long-Evans rats. 5-Hydroxyindoleacetic acid concentrations were higher in rats, while no significant between-species difference was found with respect to 3,4-dihydroxyphenylacetic acid (DOPAC), serotonin or protein concentrations. In gerbils, HVA and DOPAC occurred in approximately equal concentrations, suggesting that the formation of HVA may be of greater significance for the termination of transmitter function in the gerbil than in the rat.

Locus coeruleus lesions in the rat enhance the antinociceptive potency of centrally administered clonidine but not morphine

The nucleus locus coeruleus (LC) has been implicated in the descending inhibition of spinal nociceptive dorsal horn neurons, spinal nociceptive reflexes and in the antinociception produced by morphine. To further explore the involvement of the LC in antinociception, bilateral electrolytic lesions in the LC were made in adult male Sprague-Dawley rats. Lesions in the LC did not alter the antinociception produced by morphine (2.5 and 5 micrograms) administered in the periaqueductal gray in either the tail-flick (TF) or hot-plate (HP) tests when tested 7 and 14 days after the lesions. Baseline nociceptive thresholds in the TF and HP tests likewise were not affected at 7 or 14 days post-lesion. In contrast, the antinociceptive potency of clonidine administered intrathecally on day 13 post-lesion was enhanced significantly in the TF test; the antinociceptive ED50 of the LC lesion group was 0.52 micrograms whereas that of the sham lesion group was 2.29 micrograms. The antinociceptive potency of clonidine administered systemically (750 and 500 micrograms/kg, s.c.) was also enhanced in the LC lesion group in the TF but not the HP test. Norepinephrine (NE) in the lumbar spinal cord was correlated negatively and significantly with the extent of destruction of the LC. The lumbar spinal content of NE was reduced maximally at 12 days post-lesion (to 56% of control). The binding of [3H]clonidine in the lumbar spinal cord was slightly greater in the LC lesion than sham lesion group; the Bmax values were 42.4 fmol/mg protein and 35.5 fmol/mg protein for the LC lesion and sham lesion groups, respectively. It is suggested that the LC participates in the descending inhibition of spinal nociceptive transmission and that this inhibition may be mediated in the spinal cord by alpha-2 adrenoceptors located postsynaptically with respect to the NE terminals of the spinopetal LC efferents.

Repetitive measurement of monoamine metabolite levels in cerebrospinal fluid of conscious rats: effects of reserpine and haloperidol

A simple high performance liquid chromatographic method with electrochemical detection is described for the simultaneous determination of unconjugated 3-methoxy-4-hydroxyphenylglycol (MHPG), 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA), the principal central nervous system (CNS) metabolites of noradrenaline, serotonin and dopamine (DA), respectively, in small samples of cisternal cerebrospinal fluid (CSF) obtained repeatedly from freely moving rats. Amounts of 30-50 microliter of CSF could be collected repeatedly every 30-60 min allowing monitoring of monoamine metabolite concentration levels in CSF under physiological conditions. None of the metabolites showed any clear diurnal variation. A single injection of reserpine caused a prominent elevation in the concentrations of MHPG, 5-HIAA and HVA in CSF. However, after a rapid increase, the concentration of MHPG was decreased by 85% from the control values. Haloperidol caused a 3-fold increase in the concentration of HVA, indicating increased DA turnover in the CNS. The method enables the reliable quantitative determination of three major monoamine metabolites in small samples of CSF from freely moving rats and appears to be a useful tool in the evaluation of the validity of the clinically used research methods of monitoring drug-induced alterations in CNS monoaminergic activity by metabolite measurements in CSF.

A method for very rapid determinations of catechols using ion-pairing reverse phase HPLC with electrochemical detection: effects of L-dopa treatment on the catechol content in various rat brain structures

A simple and rapid method for determination of 12 catechols (9 endogenous and 3 internal standards, i.s.) using ion-pairing reverse phase HPLC with electrochemical detection is presented. This study basically concentrates on the importance of optimizing the mobile phase composition in isocratic systems where ordinary 25 cm X 4.6 mm i.d. columns are used. Mobile phase compositions for three different purposes are reported: 1) separation of 9 endogenous catechols, possibly occurring in the samples, and 3 i.s. in a moderately short retention time (tR) (L-DOPA, DOPEG, alpha-Methyldopa (alpha-MeDOPA, i.s.), Noradrenaline (NA), DOPAC, Adrenaline (A), Dihydroxybensylamine (DHBA, i.s.), Norsalsolinol (NS), Dopamine (DA), Epinine (EPI), Salsolinol (S) and Isoprenaline (ISO, i.s.) within 11 min), 2) ultra rapid separation of detectable endogenous catechols except L-DOPA (NA, DOPAC, A, DHBA (i.s.), NS and DA within 5.2 min and with S within 5.7 min) and 3) moderately fast separation of detectable endogenous catechols (L-DOPA, NA, A, DHBA (i.s.), NS, DOPAC and DA within 7.6 min and with S within 10 min). By balancing the pH, concentration of organic modifier (2-propanol) and pairing ion (1-heptanesulphonic acid) as well as preconditioning new columns with more packing material (Nucleosil 5 micron C18) and to high pressures (5000 psi) for 7 days, very fast separations with good baseline resolution between the peaks are possible. The method was applied on L-DOPA treated rats (100 mg/kg), where the catechol content was analysed in 7 different brain structures during the time course of synthesis and degradation (4 hours) of catechols from L-DOPA.

Simultaneous determination of 5-hydroxytryptophan and 3,4-dihydroxyphenylalanine in rat brain by HPLC with electrochemical detection following electrical stimulation of the dorsal raphe nucleus

HPLC coupled with electrochemical detection was used to make concurrent measurements of the rate of accumulation of 5-hydroxytryptophan and 3,4-dihydroxyphenylalanine in selected brain regions (striatum, nucleus accumbens, septum, medial periventricular hypothalamus) and thoracic spinal cords of rats treated with NSD 1015, an inhibitor of aromatic-L-amino-acid decarboxylase. 5-Hydroxytryptophan and 3,4-dihydroxyphenylalanine accumulated in all brain regions 30 min after the intravenous infusion of various doses of NSD 1015; there were no significant differences in the responses to 12.5, 25, 50, and 100 mg/kg. After the intravenous administration of 25 mg/kg NSD 1015 the concentrations of 5-hydroxytryptophan and 3,4-dihydroxyphenylalanine increased linearly with time in all brain regions for at least 30 min. Electrical stimulation of 5-hydroxytryptamine neurons in the dorsal raphe nucleus for 30 min at 5 or 10 Hz increased 5-hydroxytryptophan accumulation in all brain regions but not in the spinal cord. Unexpectedly, this stimulation also increased the accumulation of 3,4-dihydroxyphenylalanine in the hypothalamus and spinal cord. These results suggest that 5-hydroxytryptophan accumulation following the administration of NSD 1015 is a valid index of 5-hydroxytryptamine neuronal activity in the brain.

Concentrations of homovanillic acid and 5-hydroxyindoleacetic acid in cerebrospinal fluid from human infants in the perinatal period

To assess maturation of central serotonin and catecholamine pathways at birth, we measured lumbar CSF homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA), stable acid metabolites of dopamine and serotonin, using HPLC with electrochemical detection. CSFs from 57 neonates (38 premature and 19 at term) and 13 infants 1-6 months old were studied. HVA levels increased with maturity (p less than 0.05; ANOVA), whereas 5-HIAA levels were similar in all these subjects. HVA/5-HIAA ratios increased markedly from 1 +/- 0.12 in the most premature neonates to 1.98 +/- 0.17 in the older infants (p less than 0.01; t test). There were no sex differences for these values.

Effects of neonatal monosodium glutamate (MSG) treatment on the hormonal and central monoaminergic dynamics associated with acute ether stress in the male rat

Neonatal treatment with monosodium glutamate (MSG) induces severe neurochemical damage to several brain regions, and these lesions are expressed in adult life by a variety of endocrine and behavioral abnormalities. The present study analyzes the extent of the neurochemical damage to several monoaminergic systems by evaluating the changes in norepinephrine (NE), dopamine (DA), and 5-hydroxytryptamine (5-HT) metabolism induced by the neurotoxin in several discrete hypothalamic loci. Moreover, the study also evaluated the ability of MSG-treated rats to respond to acute ether stress, by measuring the release of ACTH and prolactin induced by ether and correlating those changes with the alterations in monoamine metabolism in the arcuate (AN), dorsomedial (DMN), and suprachiasmatic (SCN) nuclei and in the median eminence (ME). The results indicate that MSG treatment induces marked changes in monoamine metabolism in several of the regions examined. The metabolite of DA, dihydroxyphenylacetic acid, was markedly depressed in the AN, SCN, and DMN. NE metabolism was also significantly lower in the AN of MSG-treated animals. 5-HT metabolism was also altered by MSG treatment, with significant decrements recorded in the SCN, DMN, and AN. Both control and MSG-treated rats showed highly significant increments in ACTH and PRL release 5 and 15 min after exposure to ether vapors. The only quantitative difference between the two groups was a smaller increment in ACTH levels 5 min after ether in the MSG group. Ether stress increased DA metabolism in the AN, NE metabolism in the AN and DMN, and 5-HT metabolism in the SCN in control animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Liquid chromatographic assay for CSF catecholamines using electrochemical detection

A liquid chromatographic assay for noradrenaline (NA), dopamine (DA), and 3,4-dihydroxyphenylacetic acid (DOPAC) in human and monkey cerebrospinal fluid (CSF) is described. The limits of sensitivity vary between 0.1-0.3 pmol/ml of each catechol. Within-day precision as indicated by mean coefficient of variation (CV) of five days varied between 8.0-14.8 for NA (3.0-0.1 pmol/ml), 6.9-27.4 for DA (6.0-0.1 pmol/ml), and 4.1-17.6 for DOPAC (30-1 pmol/ml). Between-day precision (CV) was estimated to be 12.3, 14.9 and 16.6 for 4 pmol/ml of NA, DA and DOPAC, respectively. The method was reproducible enough for reliable quantitation of CSF free NA and DOPAC levels at physiological concentrations while the sensitivity for DA was too low to measure the free amine in less than 3 ml of human lumbar CSF. After acid hydrolysis total (free + conjugated) DA can, however, be quantified in CSF. Ranges for CSF NA and DOPAC levels were 0.13-2.0 and 0.43-14.6 pmol/ml in normal volunteers (n = 72), 0.19-3.19 and 0.7-7.09 pmol/ml in untreated chronic schizophrenic patients (n = 52), and 1.1-3.2 and 9.8-22.7 pmol/ml in rhesus monkeys (n = 8), respectively.

Manipulation of mobile phase parameters for the HPLC separation of endogenous monoamines in rat brain tissue

Multi-component mobile phases are common in ion pair reverse phase high performance liquid chromatography for the analysis of endogenous monoamines in rat brain tissue. By examining the effects of each component of a mobile phase on the separation of a number of monoamines and their metabolites, we show how optimization of parameters can achieve and/or maintain a separation both within and between different octadecyl columns. The assay itself is rapid, sensitive, demands minimal sample preparation, and results in complete resolution of the amines. More importantly, the basis for the manipulation of mobile phase components is discussed with regard to practical utilization in selective amine separation. We conclude that knowledge of mobile phase parameters, their mechanism, and manipulation is as important as the assay itself.

Monoamine metabolites in human cerebrospinal fluid. HPLC/ED method

Catecholamines and indolealkylamines are of clinical interest in neurological and psychiatric disorders. We measured 3-methoxy-DOPA, 3-methoxy-4-hydroxyphenylglycol, dihydroxyphenylacetic acid, tryptophan, 5-hydroxyindoleacetic acid and homovanillic acid in human cerebrospinal fluid with a simple, sensitive , inexpensive, rapid and accurate procedure using high performance liquid chromatography coupled to an electrochemical detector. Patients with Parkinson's disease have a decrement in homovanillic acid that is reversed by treatment with L-3,4-dihydroxyphenylalanine. After this medication, 3-methoxy-DOPA is measurable in cerebrospinal fluid. Patients with depression show a decrease in serotonin turnover expressed by diminished 5-hydroxyindoleacetic acid content in cerebrospinal fluid. Depressed patients also show low levels of tryptophan. Monoamine metabolites are augmented in patients with subarachnoid hemorrhage.

Simultaneous measurement of tyrosine, tryptophan and related monoamines for determination of neurotransmitter turnover in discrete rat brain regions by liquid chromatography with electrochemical detection

Concomitant measurement of monoamine neurotransmitter turnover in discrete rat brain areas with the use of radiolabeled amino acid precursors permits simultaneous evaluation of interacting transmitter systems. [3H]Tyrosine and [3H]tryptophan were administered via indwelling catheters to unrestrained rats. Content and specific activity of norepinephrine, dopamine, 5-hydroxytryptamine, and the metabolites dihydroxyphenylacetic acid, homovanillic acid, and 5-hydroxyindoleacetic acid in addition to tyrosine and tryptophan were quantified by liquid chromatography with electrochemical detection and liquid scintillation counting. The method employs a simple extraction procedure without prior cleanup for chromatography. Neurotransmitter turnover rates that incorporated tyrosine- or tryptophan-specific activities were found to be two to four times greater than those that did not include them.

Reduced haloperidol: effects on striatal dopamine metabolism and conversion to haloperidol in the rat

Acute injection of rats with either haloperidol or reduced haloperidol (1 mg/kg, IP) greatly increased the striatal concentrations of the acidic dopamine metabolites, indicating enhanced turnover of dopamine. The effect of reduced haloperidol was almost as great as that of haloperidol. Reduced haloperidol, however, was much less efficient (about 400 times) than haloperidol in displacing [3H]spiperone binding to striatal membranes in vitro. In agreement with the above results, reduced haloperidol was found to be oxidized to haloperidol, so that 2 h after injection of reduced haloperidol the concentrations of haloperidol and reduced haloperidol were equal in the striatum. The apparent conversion of reduced haloperidol to haloperidol was much quicker in liver than in plasma or brain, and it is suggested that the conversion primarily occurs in the liver. Before drawing any definite conclusion about the possible central activity of reduced haloperidol, further studies with other animal species are needed.

Determination of picogram levels of brain catecholamines and indoles by a simplified liquid chromatographic electrochemical detection method

A simple and rapid method for the simultaneous determination of norepinephrine, epinephrine, dopamine, 5-hydroxytryptamine and 5-hydroxyindoleacetic acid in rat brain regions by high-performance liquid chromatography (HPLC) with electrochemical detection has been developed. Perchloric acid extracts of the tissue were directly analyzed in the HPLC system. Each of these compounds gave a linear response over the range of 10-320 ng/ml cerebellar homogenate (0.2-6.4 ng on column). Analytical recoveries of these compounds added to the homogenates were complete when compared with standards dissolved in perchloric acid. The average between-run coefficients of variation for all these compounds were lower than 6.7%, over the range of 10-320 ng/ml, whereas the within-run coefficients of variation at 10 ng/ml were lower than 6.9%. Under the present instrumental and mobile phase conditions, all compounds were readily oxidized at 0.72 V vs. a Ag/AgCl reference electrode. The present method has been applied to a study determining the basal levels of these compounds in several rat brain regions as well as levels after medium raphe lesions.

An automated method for the determination of biogenic amines and their metabolites by high-performance liquid chromatography

An automated high-performance liquid chromatographic method has been developed that allows for the determination of a number of compounds related to catechol- and indoleamine metabolism. The compounds that can be measured include L-DOPA, dopamine, dihydroxyphenylacetic acid, homovanillic acid, 3-methoxytyramine, norepinephrine, 3-methoxy-4-hydroxyphenylglycol, dihydroxyphenylglycol, vanilmandelic acid, epinephrine, 5-hydroxytryptophan, serotonin, 5-hydroxyindoleacetic acid, and 5-hydroxytryptophol. Dihydroxybenzylamine is used as an internal standard. Although dihydroxyphenylglycol and vanilmandelic acid could be detected and quantified, they could not be separated from each other. The method is completely automated and is sensitive enough to detect amounts as low as 500 fmol. Up to 200 samples a week can be analyzed in the automated mode. Using this method, analyses of brain tissue can be accomplished with no need for a cleanup procedure. The value of this procedure lies in its ability to simultaneously determine various amines and metabolites from small tissue samples in the same animals and with automation to analyze a relatively large number of samples a day with little attention by a technician.

Assay procedures for the determination of biogenic amines and their metabolites in rat hypothalamus using ion-pairing reversed-phase high-performance liquid chromatography

Procedures are described for the simultaneous determination, by high-performance liquid chromatography of adrenaline, noradrenaline, dopamine and 5-hydroxytryptamine using laurylsulphate as pairing ion and for the separate simultaneous determination of vanillylmandelic acid, dihydroxyphenylacetic acid, 3-methoxy-4-hydroxyphenylethylene glycol, 5-hydroxyindoleacetic acid and homovanillic acid using tetraethylammonium as pairing ion. Sample preparation consists of protein precipitation only and octadecylsilane coated silica is used for both sets of determinations as is electrochemical detection. The chromatographic basis of each separation is discussed in the light of modern ideas of ion exchange and desolvation to enable the method to be modified chromatographically if other compounds are to be resolved or the assay method modified. The quantitative aspects of the methods are detailed and applied to amine and metabolite levels in rat hypothalamus. The values determined together with their sample variation and estimated limits of detection are quoted.

Measurement of 5-hydroxytryptamine synthesis and metabolism in selected discrete regions of the rat brain using high performance liquid chromatography and electrochemical detection: pharmacological manipulations

High performance liquid chromatography coupled with electrochemical detection (LCEC) was employed to measure 5-hydroxytryptamine (5-HT), 5-hydroxyindole-3-acetic acid (5-HIAA) and 5-hydroxytryptophan (5-HTP) in the suprachiasmatic (SCN), medial preoptic (MPO) and arcuate (AN) nuclei as well as the median eminence (ME) and striatum (ST) of individual rat brains. Biochemical estimations of changes in 5-HT neuronal activity were made by measuring: (1) concentrations of 5-HT and 5-HIAA and (2) the rate of 5-HT synthesis (5-HTP accumulation following the administration of NSD 1015, an inhibitor of aromatic L-amino acid decarboxylase) after the administration of pharmacological agents known to influence these neurons. Pargyline increased the concentration of 5-HT and decreased the concentration of 5-HIAA while probenecid increased the concentration of 5-HIAA in all 5 brain regions. At both 2 and 24 hours after reserpine the concentration of 5-HT decreased, 5-HIAA increased or did not change, and the rate of 5-HT synthesis increased. In most of the brain regions blockers of 5-HT neuronal uptake (fluoxetine, chlorimipramine) did not influence 5-HT or 5-HIAA concentrations dramatically, but increased the rate of 5-HT synthesis. L-tryptophan generally increased the concentrations of 5-HT and 5-HIAA as well as the rate of accumulation of 5-HTP in all regions except the ME where 5-HIAA and 5-HTP concentrations both were unaffected. These results reveal that the method using LCEC is sensitive enough to detect pharmacologically-induced changes in 5-HT metabolism and synthesis in discrete regions of rat brain. The drugs examined in the present study generally caused similar changes in 5-HT dynamics in all 5 brain regions examined.

The effect of morphine on 5-hydroxytryptamine synthesis and metabolism in the striatum, and several discrete hypothalamic regions of the rat brain

The effects of morphine on 5-hydroxytryptamine (5-HT) synthesis (accumulation of 5-hydroxytryptophan following inhibition of aromatic L-amino acid decarboxylase) and metabolism (concentration of 5-HT and its primary metabolite, 5-hydroxyindole-3-acetic acid [5-HIAA]) were determined in discrete nuclei of the rat brain using high performance liquid chromatography coupled with electrochemical detection (LCEC). Morphine (10 mg/kg, s.c.) increased 5-HT synthesis in the medial preoptic (MPO), suprachiasmatic (SCN) and arcuate (AN) nuclei as well as the striatum (ST) 1 hour following its administration. 5-HT synthesis in the median eminence (ME) was not affected at any time examined. A lower dose of morphine (5 mg/kg) also stimulated 5-HT synthesis in the AN. Although steady state concentrations of 5-HT were not greatly affected by morphine administration, the concentration of 5-HIAA in the AN, MPO, and ST increased following morphine (10 mg/kg, s.c., 1 hour). The increase in 5-HT synthesis observed in the MPO, SCN, AN, and ST 1 hour following morphine involved the activation of opiate receptors as administration of an opiate receptor antagonist, naloxone, blocked this effect. These results, indicate that morphine causes an increase in 5-HT synthesis and metabolism via an opiate receptor-mediated mechanism in the AN, MPO, SCN, and ST but not in the ME.