Modulation of In Vivo Striatal Transmitter Release by Nitric Oxide and Cyclic GMP

Abstract: The effects of nitric oxide (NO) and cyclic GMP on in vivo transmitter release in the rat striatum were investigated using microdialysis sampling in urethane-anaesthetised animals. The NO release-inducing substances S -nitrosoacetylpenicillamine (SNAP), S -nitrosoglutathione (SNOG), and sodium nitroprusside (SNP) increased extracellular concentrations of aspartate (Asp), glutamate (Glu), γ-aminobutyric acid (GABA), taurine (Tau), acetylcholine (ACh), and serotonin (5-HT). Dopamine (DA) concentrations were decreased by SNAP but were increased by SNOG and SNP. An NO scavenger, haemoglobin, blocked or reduced the effects of SNAP on transmitter release. However, the control carrier compounds for SNAP, SNOG, and SNP (penicillamine, glutathione, and potassium ferricyanide, respectively, which do not induce release of NO) also increased GABA, Tau, DA, and 5-HT concentrations. When NO gas was given directly by dissolving it in degassed Ringer's solution, DA concentrations decreased significantly, and those of Asp, Glu, GABA, Tau, ACh, and 5-HT increased. These effects of NO gas were all inhibited by coadministration of haemoglobin and for GABA, Tau, ACh, and DA showed some calcium dependency. The cyclic GMP agonists 8-bromo-cyclic GMP and dibutryl-cyclic GMP stimulated dose-dependent increases in Asp, Glu, GABA, Tau, ACh, DA, and 5-HT concentrations. Increased striatal transmitter release in response to NO may therefore be mediated by its stimulatory action on cyclic GMP formation. NO inhibition of DA release may be mediated indirectly through its stimulation of local cholinergic and GABAergic neurones.     

Effects of K-stimulation and precursor loading on the in vivo release of dopamine, serotonin and their metabolites in the nucleus accumbens of the rat

The efflux of endogenous 3,4-dihydroxyphenylethylamine (DA) 5-hydroxytryptamine (5-HT), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) in the nucleus accumbens of the anesthetized rat was studied using a push-pull cannula. Local perfusion for 10 minutes with 35 mM K⁺ significantly (P<0.01) increased the release of DA and 5-HT, but not their metabolites, from their respective control levels of 0.95 and 0.04 pmol/15 min to 2.5 and 0.23 pmol/15 min. Exposure to 35 mM K⁺ a second and third time resulted in a decrement in the amount of stimulated release for both DA and 5-HT. This decrease was prevented by local perfusion for 10 minutes with 50 uM L-tyrosine and -tryptophan starting 30 minutes before each episode of depolarization. The baseline amounts of DOPAC, HVA and 5-HIAA observed in the perfusates were several fold higher than the basal levels found for 5-HT and Da. In the absence of precursors, the efflux of DOPAC, HVA and 5-HIAA decreased approximately 60, 40 and 25%, respectively, from the first to the last baseline fraction collected. Addition of precursors prevented the decrease for DOPAC and 5-HIAA but not for HVA. The data indicated that (a) the release of DA and 5-HT, along with their metabolites, could be simultaneously measured with the present procedure, and (b) when using the push-pull cannula, local perfusion with precursors may be necessary following periods of sustained and/or repeated stimulation in order to replenish the monoamine transmitter pools.     

Determination of dansylated monoamine and amino acid neurotransmitters and their metabolites in human plasma by liquid chromatography-electrospray ionization tandem mass spectrometry

The determination of neurotransmitters (NTs) and their metabolites facilitates better understanding of complex neurobiology in the central nervous system disorders and has expanding uses in many other fields. We present a liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI/MS/MS) method for the quantification of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), norepinephrine (NE), vanillymandelic acid (VMA), 3-methoxy-4-hydroxy phenylglycol (MHPG), 5-hydroxytryptamine (5-HT), 5-hydroxyindole-3-acetic acid (5-HIAA), glutamate (Glu), and γ-aminobutyric acid (GABA). The NTs and their metabolites were dansylated and analyzed by an LC gradient on a C18 column on-line with a tandem mass spectrometer. This method exhibited excellent linearity for all of the analytes with regression coefficients higher than 0.99. The lower limit of quantification (LLOQ) values for DA, DOPAC, HVA, NE, VMA, MHPG, 5-HT, 5-HIAA, Glu, and GABA were 0.57, 0.37, 0.35, 0.40, 0.35, 0.91, 0.27, 0.43, 0.65, and 1.62 pmol/ml, respectively. The precision results were expressed as coefficients of variation (CVs), ranging from 1.5% to 13.6% for intraassay and from 2.9% to 13.7% for the interassay. This novel LC-ESI/MS/MS approach is precise, highly sensitive, specific, and sufficiently simple. It can provide an alternative method for the quantification of the NTs and their metabolites in human plasma.     

Effects of acute 17alpha-methyltestosterone,acute 17beta-estradiol,and chronic 17alpha-methyltestosterone on dopamine,norepinephrine and serotonin levels in the pituitary,hypothalamus and telencephalon of rainbow trout (Oncorhynchus mykiss)

This study investigated: (a) the effects of acute 17alpha-methyltestosterone (MT) or 17beta-estradiol (E(2)) administration on norepinephrine (NE), dopamine (DA), serotonin (5-HT), 3,4, dihydroxyphenylacetic acid (DOPAC), and 5-hydroxyindoleacetic acid (5-HIAA) contents in the hypothalamus, telencephalon and pituitary of previtellogenic female rainbow trout Oncorhynchus mykiss, and (b) the effects of chronic MT administration on the levels of these neurotransmitters in these brain regions in immature male rainbow trout. The acute administration of MT induced a significant decrease in pituitary levels of DOPAC as well as in the DOPAC/DA ratio. On the other hand, the acute administration of E(2) induced an increase in pituitary 5-HT levels as well as a decrease in the 5-HIAA/5-HT ratio. In a second experiment, 20 mg MT per kilogram body weight was implanted for 10, 20 or 40 days into sexually immature male rainbow trout. Implanted rainbow trout showed increased testosterone and decreased E(2) levels. In the pituitary, MT induced long-term decreases in NE, DA, DOPAC and 5-HT levels, as well as in the DOPAC/DA ratio. Hypothalamic and telencephalic DA, NE and 5-HT levels were not affected by MT implantation. However, 5-HIAA levels and the 5-HIAA/5-HT ratio were reduced by MT implantation in both brain regions. These results show that chronic treatment with MT exerts both long-term and region-specific effects on NE, DA, and 5-HT contents and metabolism, and thus that this androgen could inhibit pituitary catecholamine and 5-HT synthesis. A possible role for testosterone in the control of pituitary dopaminergic activity and gonadotropin II release is also discussed.     

Significant correlation between cerebrospinal fluid and brain levels of norepinephrine, serotonin and acetylcholine in anesthetized rats

The present study was undertaken to determine cerebrospinal fluid (CSF) and brain levels of norepinephrine (NE), serotonin (5-HT) and their metabolites--3,4-dihydroxyphenylacetic acid (DOPAC), 4-hydroxy-3-methoxyphenylacetic acid (HVA) and 5-hydroxyindole-3-acetic acid (5-HIAA)--in rats pretreated with 6-hydroxydopamine (6-OHDA) or 5,7-dihydroxytryptamine (5,7-DHT). In the 6-OHDA pretreated rats, both CSF and brain concentrations of NE, DOPAC and HVA sustained significant decreases as compared with those in non-treated rats. Positive and significant correlations between CSF and brain levels were observed in respect to NE, DOPAC and HVA. In 5,7-DHT pretreated rats, both CSF and brain concentrations of 5-HT and 5-HIAA were significantly decreased. A positive and significant correlation between CSF and brain levels in respect to 5-HT and 5-HIAA was observed. Further studies were carried out to determine ACh levels of both the CSF and the brain in microspheres (MS)-treated rats, which are used as a model of microembolization. The CSF ACh concentrations in MS-treated groups were significantly decreased as compared with those in non-treated rats. The brain ACh contents also tended to decrease in this group. A positive and significant correlation was observed between CSF and brain levels of ACh. These findings suggest that NE, 5-HT and ACh concentrations in the CSF are direct indications of central noradrenergic, serotonergic and cholinergic nerve activity, respectively.     

Role of Adenylate Cyclase in the Modulation of the Release of Dopamine: A Microdialysis Study in the Striatum of the Rat

In the present study, we have applied the brain microdialysis technique to investigate the effect of the stimulation of adenylate cyclase on the extracellular levels of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA) in the striatum of freely moving rats. Infusion of 8-bromo-adenosine 3',5'-cyclic monophosphate (8-Br-cAMP), 3-isobutyl-1-methylxanthine, or forskolin produced a significant increase in the release of DA. The effect of 8-Br-cAMP was tetrodotoxin, Ca2+, and dose dependent and was saturable. 8-Br-cAMP also caused an increase in the output of DOPAC and HVA. No effects were seen on the output of 5-HIAA, except at the highest 8-Br-cAMP concentration studied. Infusion of 8-Br-cAMP (25 microM, 1.0 mM, and 3.3 mM) together with infusion of (-)-sulpiride (1 microM) or systemic administration of (+/-)-sulpiride (55 mumol/kg i.p.) produced an additive effect on the release of DA. Infusion or peripheral administration of (-)-N-0437 (1 microM or 1 mumol/kg) both decreased the 8-Br-cAMP-induced increase in the release of DA. These results demonstrate that cyclic AMP may stimulate the release of DA, but it is unlikely that this second messenger is linked to presynaptic D2 receptors controlling the release of DA.     

Effects of Chronic Ethanol Consumption and Aging on Dopamine, Serotonin, and Metabolites

Abstract: This study examined the hypothesis that chronic ethanol consumption results in significant abnormalities in both the dopaminergic and the serotonergic system of aged rats. Levels of dopamine (DA), serotonin [5-hydroxytryptamine (5-HT)], 3,4-dihydroxyphenylacetic acid (DOPAC), and 5-hydroxyindole-3-acetic acid (5-HIAA) were determined in brain areas of both the nigrostriatal and mesocorticolimbic DA systems in 5-, 14-, and 24-month-old male Fischer 344 rats. Aging was associated with a reduced concentration of DA in the striatum (ST), ventral tegmental area (VTA), and ventral pallidum (VP) and an increased concentration of 5-HIAA in the ST, globus pallidus, nucleus accumbens, frontal cortex, and VP. In addition, there was an increase in the 5-HIAA/5-HT ratio in all brain areas analyzed. Six weeks of ethanol consumption was accompanied by significant changes in mesocorticolimbic brain areas. In the VTA of 5-month-old ethanol-fed rats DA content was decreased to the levels found in aged rats, e.g., 24 months of age. Ethanol also significantly lowered 5-HT and 5-HIAA contents in the VTA and reduced DOPAC and 5-HIAA levels in the VP. In addition, ethanol blunted the normal age-related increase in 5-HIAA/5-HT ratio in the VTA, VP, and substantia nigra. It is interesting that although the age-related changes were found in both nigrostriatal and mesocorticolimbic brain areas, the ethanol-associated effects were found only in brain areas of the mesocorticolimbic system. The changes in DA and 5-HT function that accompany aging and ethanol consumption may contribute to the problems in motor function and ethanol abuse found in the aged.     

Neocortical Dialysate Monoamines of Rats After Acute, Subacute, and Chronic Liver Shunt

Abstract: Intracerebral microdialysis was applied to monitor the neocortical extracellular levels of the aromatic amino acids phenylalanine, tyrosine, and tryptophan, the neurotransmitters dopamine (DA), noradrenaline (NA), and serotonin (5-HT), and the metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindole-3-acetic acid (5-HIAA) in rats with various forms of experimental hepatic encephalopathy (HE). The extracellular aromatic amino acid levels were clearly increased in acute, subacute, and chronic HE. No changes compared with controls in the neocortical DA release could be detected in the three experimental HE rat models investigated. The NA release showed a significant increase only in the subacute HE group. These data suggest that HE may not be associated with any major reduction of neocortical DA or NA release as previously suggested. In acute and subacute HE, decreased extracellular DOPAC but elevated 5-HIAA concentrations were seen. In chronic HE, elevations of both DOPAC and 5-HIAA were observed. Neocortical 5-HT release did not change in subacute and chronic HE, whereas it decreased in acute HE compared with control values. Significant increase in extracellular concentrations of 5-HIAA and of the 5-HIAA/5-HT ratio in the present study are in agreement with previously reported increases in 5-HT turnover in experimental HE. However, a substantially increased 5-HT turnover in experimental HE does not appear to be related to an increase in neuronal neocortical 5-HT release.     

Prefrontal-limbic Change in Dopamine Turnover by Acupuncture in Maternally Separated Rat Pups

The present study investigated the possible role of acupuncture in alleviating depression-like behavioral changes and examined changes in the levels of serotonin (5-HT), dopamine (DA), and their metabolites in the hippocampus (HP) and prefrontal cortex (PFC) of maternally separated rat pups. On postnatal day 15, rat pups were maternally separated and received acupuncture stimulation at acupoint HT7 or ST36 once a day for 7?days. Then, on postnatal day 21, a tail suspension test was performed, and the HP and PFC were harvested. Levels of 5-HT, 5-hydroxyindole-3-acetic acid (5-HIAA), DA, and 3,4-dihydroxyphenylacetic acid (DOPAC) in the tissue and corticosterone (CORT) in plasma were then measured. The total duration of immobility in maternally separated rat pups increased after maternal separation, and this increase was alleviated by acupuncture stimulation at HT7. The 5-HIAA/5-HT ratio and the levels of 5-HT and 5-HIAA were not significantly changed, but those of the DA and the DOPAC/DA ratio were significantly lower and that of CORT was significantly higher after maternal separation. The maternal separation-induced changes of the DOPAC/DA ratio and the CORT level significantly alleviated after acupuncture stimulation at HT7. These results suppose that the functional recovery of prefrontal-limbic system by acupuncture stimulation plays an important role in acupuncture-induced benefits in this animal model of depression.     

Rat brain monoamine and serotonin S2 receptor changes during pregnancy

The concentrations of noradrenaline (NA), dopamine (DA), serotonin (5-HT), and their metabolites were determined in 5 brain areas of non-pregnant, 15 and 20 day pregnant and 4 day post-partum rats. Striatal 5-HT content was significantly lower in 15 and 20 day pregnant rats than in estrous controls. A significant decrease in striatal and frontal cortex 5-hydroxyindole-3-acetic acid (5-HIAA) concentration was observed in 15 day pregnant rats. Significant increases in hypothalamic and hippocampal NA levels were observed at 4 days post-partum. Frontal cortex serotonin S2 receptorKd was reduced in 4 day post-partum rats. There was no significant change in S2 receptorB _max during pregnancy. Levels of progesterone were negatively correlated with striatal DA, homovanillic acid (HVA), 5-HT, and 5-HIAA levels, hypothalamic DA, hippocampal 5-HT, and frontal cortex 5-HIAA values as well as striatal HVA to DA, and HVA to 3,4-dihydroxyphenylacetic acid (DOPAC) ratios and amygdaloid HVA to DOPAC ratios. The limbic neurotransmitter changes might possibly contribute to mood changes which occur during pregnancy and post-partum.     

Intracerebrally administered (6r)-l-erythro-tetrahydrobiopterin does not affect extracellular levels of dopamine and serotonin metabolites in rat striatum in vivo during measurement by brain micro-dialysis system

By the use of the brain micro-dialysis technique combined with HPLC, the changes in the extracellular levels of dopamine (DA) and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), and a serotonin(5-HT) metabolite, 5-hydroxyindoleacetic acid (5-HIAA) were examined in the rat striatum before and after intracerebral injection of a vehicle or (6R)-l-erythro-tetrahydrobiopterin (6R-BH₄), the natural form of the cofactor for the tryrosine hydroxylase and tryptophan hydroxylase. No apparent change after the 6R-BH, treatment was found in the levels of DA, DOPAC, HVA and 5-HIAA in the striatal dialysate. In contrast, the levels of total biopterin in both the operated (dialysis probe-implanted) and unoperated striatum of 6R-BH₄-treated rats increased by 23- and 93-fold, respectively, when compared with those of the control, vehicle-treated rats. The results indicate that increased levels of the tetrahydrobiopterin cofactor may not affect the release of DA and the extracellular level of DA and 5-HT metabolites in the physiologically normal brain.     

Serotonin, dopamine, noradrenaline and their metabolites: levels in the brain of the house cricket (Acheta domesticus L.) during a 24-hour period and after administration of quipazine--a 5-HT2 receptor agonist.

1. The levels of 5-HT, DA, NA and DA metabolites (NADA, DOPAC) measured by HPLC (with electrochemical detection) in the brain of the house cricket did not change over a 24-hr period. The level of 5-HIAA, a 5-HT metabolite, was below the limit of detection. 2. The 5-HT and DOPAC levels decreased and NADA increased after quipazine injection but DA and NA levels did not change after it. 3. [3H]Ketanserin was used to identify serotonin receptors bound to sites in the house cricket brain with a KD of 5 nM and a concentration of Bmax 180 fmol/mg protein.     

Lesion of caudate-putamen interneurons with kainic acid alters dopamine and serotonin metabolism in the olfactory tubercle of the rat

1. The existence of functional interrelationships between dorsal and ventral regions of the rat striatum was investigated. Kainic acid (KA) was employed to induce neuronal lesions in the more dorsal striatum, the caudate-putamen (CP). Only one CP (one side) received KA. KA-induced neurotoxicity at the site of injection (CP) was evidenced by reductions in choline-acetyltransferase activity and in GABA levels, and by increases in the ratios metabolite/monoamine for dopamine (DA) and serotonin (5-HT).2. In addition to the well-known local effects, direct stereotaxic injection of KA into the CP produced distant effects in the ipsilateral olfactory tubercle (OT). A dose-dependent increase in the levels of 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA) and decreases in DA and 5-HT concentrations were observed in the OT ipsilateral to the CP injected with KA. With 1, 2, 3, and 4 g of KA, the ratio DOPAC+HVA/DA in the OT was 30, 79, 140, and 173% higher, respectively, than control levels. With 2, 3, and 4 g of KA, the levels of 5-HIAA were approximately 30, 60, and 120% higher than control values, and the changes in 5-HIAA were associated with significant reductions in 5-HT concentrations.3. Our results suggest that the dorsal part of the striatum exerts important regulatory functions over the most ventral striatal region, the OT. Destruction of CP interneurons by KA leads to disinhibition of DA and 5-HT activities to the OT. The functional interactions between dorsal and ventral striatal regions may play a role in the integration of fundamental life-preserving, motivational, and goal-directed olfactory motor behaviors of rodents.     

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

Assays capable of measuring picomole quantities of dopamine (DA), 5-hydroxytryptamine (5-HT), several of their precursors and metabolites concurrently within 25 minutes were developed utilizing high performance liquid chromatography with electrochemical detection (LCEC). Several parameters of the LCEC were altered in order to separate the compounds while maintaining a short assay time. The final LCEC systems demonstrated biological utility in that the DA metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), and the 5-HT metabolite 5-hydroxy-3-indoleacetic acid (5-HIAA) were detected in rat cerebrospinal fluid; in addition to these compounds, DA and 5-HT were measurable in the striatum, hypothalamus and median eminence of the rat brain. Pargyline decreased the concentrations of DOPAC, HVA and 5-HIAA and increased the 5-HT concentration in all three brain regions, and increased the DA concentration in the striatum. Probenecid increased all three acid metabolite concentrations in the hypothalamus and median eminence, while only the HVA and 5-HIAA concentrations were increased in the striatum. The DA and 5-HT concentrations were unaltered. The LCEC methods described in this paper should be useful in elucidating the mechanisms and roles of 5-HT and DA neurons in experimental paradigms of biological interest.     

Role of Serotonin2A and Serotonin2B/2C Receptor Subtypes in the Control of Accumbal and Striatal Dopamine Release Elicited In Vivo by Dorsal Raphe Nucleus Electrical Stimulation

This study investigates, using in vivo microdialysis, the role of serotonin2A (5-HT2A) and 5-HT(2B/2C) receptors in the effect of dorsal raphe nucleus (DRN) electrical stimulation on dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), and 5-hydroxyindoleacetic acid (5-HIAA) extracellular levels monitored in the nucleus accumbens (NAC) and the striatum of halothane-anesthetized rats. Following DRN stimulation (300 microA, 1 ms, 20 Hz, 15 min) DA release was enhanced in the NAC and reduced in the striatum. The 5-HT2A antagonist SR 46349B (0.5 mg/kg) and the mixed 5-HT(2A/2B/2C) antagonist ritanserin (0.63 mg/kg) significantly reduced the effect of DRN stimulation on DA release in the NAC but not in the striatum. DA responses to DRN stimulation were not affected by the 5-HT(2B/2C) antagonist SB 206553 (5 mg/kg) in either region. None of these compounds was able to modify the enhancement of DOPAC and 5-HIAA outflow induced by DRN stimulation in either the NAC or the striatum. Finally, in both brain regions basal DA release was significantly increased only by SB 206553. These results indicate that 5-HT2A but not 5-HT(2B/2C) receptors participate in the facilitatory control exerted by endogenous 5-HT on accumbal DA release. Conversely, 5-HT(2B/2C) receptors tonically inhibit basal DA release in both brain regions.     

Effects of muscimol and baclofen on levels of monoamines and their metabolites in the El mouse brain

We compared the changes in monoamines and their metabolites in the El mouse brain induced by GABA-A and GABA-B receptor agonists. Muscimol was used as a GABA-A receptor agonist, and baclofen as a GABA-B receptor agonist. Muscimol (3 mg/kg) significantly increased the DOPAC level in all parts of the mouse brain and the HVA level in the cortex, striatum, and midbrain. No significant change was observed in the dopamine (DA) level. These findings suggest that muscimol may accelerate both the synthesis and catabolism of DA. Baclofen (20 mg/kg) increased the DA level in the hippocampus and midbrain, and the DOPAC level in the hippocampus. Muscimol increased 5-HIAA levels and decreased 5-HT levels. This result suggests that 5-HT metabolism is accelerated by muscimol. No change in 5-HT or 5-HIAA levels was induced by baclofen. The GABA-A receptor system seems to have a potent effect not only on DA neurons, but on 5-HT neurons. However, the GABA-B receptor system appears to have almost no effect on 5-HT neurons, though it appears to have some effect on DA neurons.     

Liquid chromatography with amperometric detection using functionalized multi-wall carbon nanotube modified electrode for the determination of monoamine neurotransmitters and their metabolites

The fabrication and application of a novel electrochemical detection (ED) method with the functionalized multi-wall carbon nanotubes (MWNTs) chemically modified electrode (CME) for liquid chromatography (LC) were described. The electrochemical behaviors of dopamine (DA) and other monoamine neurotransmitters at the CME were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results indicated that the CME exhibited efficient electrocatalytic effects on the current responses of monoamine neurotransmitters and their metabolites with high sensitivity, high stability and long-life activity. In LC-ED, DA, norepinephrine (NE), 3-methoxy-4-hydroxyphenylglycol (MHPG), 3,4-dihydroxyphenylacetic acid (DOPAC), 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) had good and stable current responses at the CME. The linear ranges of seven analytes were over four orders of magnitude and the detection limits were 2.5 x 10(-10) mol/l for DA, 2.5 x 10(-10) mol/l for NE, 5.0 x 10(-10) mol/l for MHPG, 3.0 x 10(-10) mol/l for DOPAC, 3.5 x 10(-10) mol/l for 5-HT, 6.0 x 10(-10) mol/l for 5-HIAA, 1.25 x 10(-9) mol/l for HVA. The application of this method coupled with microdialysis sampling for the determination of monoamine neurotransmitters and their metabolites in Parkinsonian patients' cerebrospinal fluid was satisfactory.     

Prenatal Exposure to Ozone Disrupts Cerebellar Monoamine Contents in Newborn Rats

Ozone (O3) is widely distributed in environments with high levels of air pollution. Since cerebellar morphologic disruptions have been reported with prenatal O3 exposure, O3 may have an effect on some neurotransmitter systems, such as monoamines. In order to test this hypothesis, we used 60 male rats taken from either, mothers exposed to 1 ppm of O3 during the entire pregnancy, or from mothers breathing filtered and clean air during pregnancy. The cerebellum was extracted at 0, 5, and 10 postnatal days. Tissues were processed in order to analyze by HPLC, dopamine (DA) levels, 3,4 dihydroxyphenilacetic acid (DOPAC) and homovanillic acid (HVA), norepinephrine (NA), serotonin, and 5-hydroxy-indole-acetic acid (5-HIAA) contents. Results showed a decrease of DA, NA, DOPAC and HVA mainly in 0 and 5 postnatal days. There were no changes in 5-HT levels, and 5-HIAA showed an increase after 10 postnatal days. DOPAC + HVA/DA ratio showed changes in 0 and 10 postnatal days, while 5-HIAA/5-HT ratio showed a slight decrease in 0 days. The data suggest that prenatal O3 exposure disrupts the cerebellar catecholamine system rather than the indole-amine system. Disruptions in cerebellar NA could lead to ataxic symptoms and also could limit recovery after cortical brain damage in adults. These finding are important given that recovery mechanisms observed in animals are also observed in humans.     

Effect of Melatonin Treatment on 24-hour Variations in Hypothalamic Serotonin and Dopamine Turnover During the Preclinical Phase of Freund's Adjuvant Arthritis in Rats

The effect of melatonin treatment on time-of-day variations in hypothalamic serotonin (5-HT) and dopamine (DA) turnover was studied in rats treated with Freund's complete adjuvant (FCA). Animals received s.c. injections of 30 æg of melatonin or vehicle 1 h before lights off for 11 days. On day 10 of treatment, FCA or its vehicle was s.c. injected, and 2 days later, the rats were killed at 6 different time intervals throughout a 24-hour cycle. Hypothalamic 5-HT, 5-hydroxyindole-3-acetic acid (5-HIAA), DA and 3,4-dihydroxyphenylacetic acid (DOPAC) levels were measured by HPLC. 5-HT and DA turnover were estimated from the 5-HIAA/5-HT and DOPAC/DA ratios, respectively. In the anterior hypothalamus, time-of-day variation in 5-HT turnover was suppressed by FCA, an effect counteracted by melatonin treatment. Melatonin also prevented FCA effect on medial hypothalamic 5-HT turnover, while in the posterior hypothalamus, similar daily variations of 5-HT turnover were found in all experimental groups. As far as DA turnover, FCA or melatonin administration suppressed its daily variations in the anterior hypothalamus. Time-of-day variations in medial hypothalamic DA turnover were similar in all groups while only rats treated with melatonin and FCA or its vehicle exhibited significant daily changes of DA turnover in the posterior hypothalamus. Results indicate that melatonin treatment affects partly the 24-hour pattern of variation of hypothalamic 5-HT and DA turnover at an early phase of FCA arthritis in rats.     

Asymmetric metabolism of hypothalamic catecholamines alternates with side of ovulation in a lizard (Anolis carolinensis).

We determined levels of monoamines and their metabolites in 2 hypothalami dissected from the right and left hemibrains of 15 females during the right-left alternating ovulatory cycle of Anolis carolinensis. Tissue contents of the following were measured using HPLC and electrochemical (coulometric) detection: dopamine (DA) and its metabolite 2,4-dihydroxyphenylacetic acid (DOPAC), norepinephrine (NE) and its metabolites 3-methoxy-4-hydroxyphenylglycol (MHPG) and 3,4-dihydroxyphenylglycol (DHPG), and serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA). An asymmetry ratio (AR) was determined by subtracting hypothalamic content (pM/mg) on the larger ovary (LO) side from that on the smaller ovary (SO) side, divided by the sum of the 2 sides (AR = SO - LO/SO+LO). The Ar of MHPG and DHPG both decreased as the largest follicle in the LO grew during the cycle, from greater than 0 (content higher on the SO side) at the beginning of the cycle to less than 0 (content higher on the LO side). The average content of MHPG in the 2 sides significantly increased during the cycle. There were no significant asymmetric changes in hypothalamic DA or DOPAC. The average content of DA increased during the cycle, whereas the content of DOPAC, as well as DOPAC/DA, did not change. The average content of 5-HT increased, and the average metabolite ratio of 5-HIAA/5-HT decreased during the cycle without significant asymmetries. The metabolite ratios of NE and DA, but not 5-HT, were asymmetric on the same side in a given female.(ABSTRACT TRUNCATED AT 250 WORDS)