High-performance Liquid Chromatography With Electrochemical Detection Research Articles

The yohimbine-induced anticonflict effect in the rat, Part II. Neurochemical findings.

In a companion paper the alpha 2-adrenoceptor antagonist yohimbine was found to produce a dose-dependent anticonflict effect in a modified Vogel's conflict test. The behavioral data further indicated that noradrenergic and serotonergic neurons as well as the benzodiazepine (BDZ) receptor may be involved in the anticonflict effect of yohimbine. In the present study the effects on rat brain monoamine neurochemistry and GABAA/BDZ receptor function (36Cl-uptake in corticohippocampal synaptoneurosomes) of a maximally anticonflict producing dose of yohimbine (4.0 mg/kg, i.p.) were studied. The levels of rat brain catecholamines and indoleamines were measured ex vivo using high performance liquid chromatography with electrochemical detection (HPLC-ED). Yohimbine decreased noradrenaline levels both in the hippocampus and the hemispheres but instead increased DOPAC levels in these brain regions as well as in the limbic forebrain. Yohimbine also markedly enhanced DOPA accumulation in the hippocampus and the hemispheres after inhibition of 1-aromatic amino acid decarboxylase by means of NSD 1015, whereas in the limbic system only a modest increase was obtained. The yohimbine-induced effects on the catecholamine synthesis rate were largely abolished in animals severely depleted of NA by means of 6-hydroxy-dopamine (6-OH-DA) pretreatment. Yohimbine decreased both the 5-HIAA/5-HT quotient (an indicator of 5-HT turnover) and 5-HTP accumulation after NSD 1015 in the hemispheres, whereas in the hippocampus and the limbic system only 5-HTP accumulation was decreased. The yohimbine-induced effect on the indoleamine synthesis rate was not influenced by 6-OH-DA pretreatment, whereas this effect and that on the catecholamine synthesis rate were both abolished by reserpine pretreatment. Neither in vivo nor in vitro administration of yohimbine significantly altered baseline or GABA-induced accumulation of 36Cl- in corticohippocampal synaptoneurosomes. In conclusion, the present study provides neurochemical support for the suggestion that yohimbine may exert its anticonflict effect in a modified Vogel's conflict test by increasing and decreasing NA and 5-HT neurotransmission, respectively, whereas no evidence was obtained for a direct interaction of yohimbine with GABAA/BDZ receptor function.

Distribution of serotonin in the sea scallopPlacopecten magellanicus

Summary Serotonin (5-HT) was detected in various body tissues of the scallop using both immunocy-tochemistry and high performance liquid chromatography with electrochemical detection (HPLC-ED). Much of the 5-HT in the body appears to originate from nerve cells in pedal and cerebral ganglia. Neuropilar regions of these ganglia are also abundant in 5-HT. Far fewer 5-HT containing cells reside within the parietovisceral ganglion, although the accessory lobe contains numerous such cells. The lateral lobes of the parietovisceral ganglion are richly innervated with 5-HT containing fibres. Immunoreactive fibres were also found in the heart, kidneys, labial palps, gills and various muscles. The digestive tract contained numerous immunoreactive cell bodies. Immunoreactive fibres were found principally around the collecting tubules of both the testes and the ovaries in the spring, but also around the germinal acini by autumn. HPLC-ED was used to quantify the amount of 5-HT present in the above-mentioned tissues in ...

Comparison of changes in extracellular dopamine concentrations in the nucleus accumbens during intravenous self-administration of cocaine or d-amphetamine

Changes in extracellular concentrations of dopamine (DA) were measured in vivo in the nucleus accumbens of the rat during intravenous self-administration of either cocaine (0.25, 0.5, 1.0mg/infusion) or d-amphetamine (0.05, 0.1, 0.2mg/infusion). Drug intake was limited to 12 self-administered infusions per session for each drug/dose combination. Changes in extra-cellular DA concentrations were measured by two different techniques: chronoamperometry in conjunction with chronically-implanted stearate-modified carbon paste electrodes, or intracerebral microdialysis with off-line analyses using high performance liquid chromatography with electrochemical detection (HPLC-ED). Significant increases in extracellular DA concentrations were observed with both in vivo techniques during self-administration of each dose of cocaine or d-amphetamine. For each drug, the magnitude of change during the first hour of the test session was comparable across doses. However, the change observed over the first 2h period, as measured by microdialysis and HPLC-ED, revealed a dose effect for cocaine, but no dose-response effect for d-amphetamine. The duration of the drug-induced elevation was increased significantly as a function of dose with both cocaine and d-amphetamine. Data from the microdialysis experiments indicated that the high dose of d-amphetamine (0.2mg/infusion) produced a significantly greater increase in extracellular DA concentrations in the nucleus accumbens than did the high dose of cocaine (1.0mg/infusion), but that comparable changes were induced by doses of 0.1mg/infusion of d-amphetamine and 1.0mg/infusion of cocaine, respectively. Each dose of both psychostimulant drugs also produced a significant decrease in dihydroxyphenylacetic acid (DOPAC) levels. The latter finding indicated that the electrochemical signal measured in these studies was not due to the oxidation of DOPAC. These results confirm that self-administration of cocaine or d-amphetamine by the rat is accompanied by a significant increase in extracellular DA concentrations in the nucleus accumbens. The fact that two different psychomotor stimulant drugs of abuse have qualitatively similar neurochemical correlates when self-administered, adds credence to the hypothesis that their reinforcing properties are related to dynamic changes in DA concentrations in the ventral striatal region of the brain.

Biochemical pathway of melanotic encapsulation of Brugia malayi in the mosquito, Armigeres subalbatus

The mosquito, Armigeres subalbatus, is naturally resistant to the filarial worm, Brugia malayi, and microfilariae (mf) penetrating the midgut are killed by melanotic encapsulation reactions in the hemocoel within 48 h following ingestion. This vector-parasite system was used to assess changes in hemolymph tyrosine, tyrosine derivatives, and catecholamine-metabolizing enzyme activities using high pressure liquid chromatography with electrochemical detection (HPLC-ED) during melanotic encapsulation reactions against mf. Tyrosine and dopa were detected in the hemolymph of both control and immune-activated (mf-exposed) mosquitoes, but not dopamine or N-acetyl dopamine (NADA). Tyrosine was significantly increased in immune-activated mosquitoes at 6 and 12 h post blood feeding, but was depleted following intrathoracic inoculation of mf in the absence of a blood meal. Dopa also was elevated in immune-activated mosquitoes at 6, 12, and 24 h post-exposure to mf. There were significant increases in phenol oxidase (PO) and dopa decarboxylase (DDC) activities in immune-activated mosquitoes as compared to controls, and these elevated activities were correlated with changes in tyrosine and dopa levels in the hemolymph. No significant differences in N-acetyl transferase (NAT) and dopachrome conversion enzyme (DCE) activities between control and immune-activated mosquitoes were observed. The possible roles these molecules play in melanotic encapsulation reactions of A. subalbatus against mf are discussed.

Decreased brain concentrations of choline and acetylcholine in mice with thioacetamide-induced acute liver failure

To investigate the alteration of the cholinergic neurotransmitter system in hepatic encephalopathy (HE), we measured the concentrations of choline (Ch) and acetylcholine (ACh) in the brain of mice with thioacetamide (TAA)-induced acute liver failure using a high-performance liquid chromatography with electrochemical detection (HPLC-ECD). The concentrations of Ch and ACh in TAA-treated mice decreased in most regional brain areas as compared to control mice. In particular, Ch significantly decreased in the cortex ( P < 0.05), hippocampus ( P < 0.01), hypothalamus ( P < 0.05), midbrain ( P < 0.01) and medulla oblongata ( P < 0.01). Similarly, ACh significantly decreased in the striatum ( P < 0.01), hippocampus ( P < 0.01), midbrain ( P < 0.01) and medulla oblongata ( P < 0.01). Our findings suggest that the suppression of the cholinergic neurotransmitter system may play a role in the pathogenesis of HE in acute liver failure.

High-performance liquid chromatographic analysis with electrochemical detection of biogenic amines using microbore columns.

High-performance liquid chromatography with electrochemical detection (HPLC-ED) is a popular method for measuring biogenic amines, owing to its simplicity, versatility, sensitivity, and specificity. Recent developments in microbore column HPLC-ED have been facilitated by miniaturization of solvent delivery, column packing, sample injection and micro-flow cell construction. The aim of this paper is to present an overview of recent developments in microbore column HPLC-ED, in terms of advantages and limitations. This paper covers the recent advancements and important factors of HPLC-ED analysis of biogenic amines using microbore columns. Particular emphasis is placed on applying this technique to microdialysis, for which great sensitivity is required. Its potential in future biomedical applications is also discussed.

Cyclic and age-related changes in norepinephrine concentrations in the medial preoptic area and arcuate nucleus

High-performance liquid chromatography with electrochemical detection (HPLC-EC) and Palkovits' microdissection technique were used to measure norepinephrine (NE) concentrations in the medial preoptic area (MPA) and arcuate nucleus (AN) during various stages of the estrous cycle. NE was measured seven times at 2-h intervals between 1000 h and 2200 h on the days of proestrus and diestrus in young (4-month-old) rats and four times at 2-h intervals between 1400 h and 2000 h in old (20–22-month-old) persistently diestrous rats. On the day of proestrus in young animals, NE increased progressively from low levels at 1000 h to peak levels at 2000 h, followed by a sharp decline at 2200 h. In contrast, no changes in NE occurred on the day of diestrus. Unlike the young proestrous rats, but similar to the young diestrous rats, no changes in NE concentrations either in the MPA or in the AN occurred in the old persistently diestrous rats. These data demonstrate that NE concentrations in the MPA and AN change during the estrous cycle. We believe the increase in NE on the aftemoon of proestrus is related to the surge in serum luteinizing hormone (LH) that occurs simultaneously in this stage of the estrous cycle. The lack of change in NE concentrations in the young diestrous and persistently diestrous old animals is consistent with the well-established absence of changes in serum LH in these animals.

α2 D-Adrenoceptors modulate renal noradrenaline release in normotensive and spontaneously hypertensive rats

The aim of the present study was to investigate α-adrenoceptor modulation of neurotransmission in kidneys of spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rat (WKY) and to classify the prejunctional α 2-adrenoceptor subtype involved. Kidneys of SHR (12–14 weeks) and age-matched WKY were isolated and the sympathetic nerves were stimulated electrically. The renal nerve stimulation-induced outflow of endogenous noradrenaline was measured by high-pressure liquid chromatography with electrochemical detection (HPLC-ECD). In the presence of uptake blockade by cocaine and corticosterone, the renal nerve stimulation-induced outflow of endogenous noradrenaline was significantly greater in SHR than in WKY at 1 Hz (688 ± 42 pg/g vs. 525 ± 46 pg/g) and 4 Hz (5265 ± 495 pg/g vs. 3544 ± 245 pg/g). At a stimulation frequency of 1 Hz the α 2-adrenoceptor agonist UK 14304 (0.01-1 μM) potently inhibited the renal nerve stimulation-induced outflow of noradrenaline with a pEC 50 of 7.49 (7.32–7.68) and a maximum of 91% in SHR and with a pEC 50 of 7.46 (7.30–7.74) and a maximum of 92% in WKY. α-Adrenoceptor antagonist affinity estimates (p K B values) against UK 14304 at the prejunctional α 2-autoreceptors were determined. The rank order of affinities (phentolamine > rauwolscine > 2-(2,6-dimethoxyphenoxyethyl) aminomethyl-1,4-benzodioxane HCl (WB 4101) > prazosin) was identical in SHR and WKY, and comparison with data from radioligand binding, molecular cloning and functional studies in other tissues and cell lines indicates that prejunctional α 2-autoreceptors of SHR and WKY kidneys are of the α 2 D subtype.

The effects of glutathione and ascorbic acid on the oxidations of 6-hydroxydopa and 6-hydroxydopamine

The interactions of ascorbic acid (AA) and reduced glutathione (GSH) in the oxidations of the catecholaminergic neurotoxins 6-hydroxydopa (TOPA) and 6-hydroxydopamine (6-OHDA) were investigated by both high performance liquid chromatography with electrochemical detection (HPLC-ED) and spectrometric methods. These comparative studies showed TOPA and 6-OHDA to be extremely AA nor GSH was found capable of significantly impeding the oxidations of these trihydroxyphenyls, or of regenerating these substances by reducing back their oxidation products, even though such a redox exchange mechanism was demonstrated for AA and the dihydroxyphenyl dopamine. Although ineffective in keeping TOPA and 6-OHDA as reduced molecules, GSH may nevertheless influence the neurotoxicity of trihydroxyphenyls by interacting with their oxidation products forming glutathionyl conjugates, thereby switching the reaction pathway away from potentially toxic eumelanin precursors and toward the production of pheomelanin. Electrochemical analyses established the formation of two oxidation products derived from each trihydroxyphenyl, one detected at −100 mV and the other at + 700 mV. AA had no effect on either oxidation product, where GSH significantly decreased the levels of both oxidation products. The component detected at + 700 mV is the cyclized, reduced leukochrome. The identity of the component detected at −100 mV was not established, but it is considered to be either the p-quinone or the cyclized, oxidized aminochrome.

Serotonin depletion affects blood-feeding but not host-seeking ability in Aedes triseriatus (Diptera: Culicidae).

The host-seeking and blood-feeding abilities of Aedes triseriatus (Say) were evaluated after treatment with the amine depleting drugs alpha-methyl-tyrosine (AMT) and alpha-methyl-tryptophan (AMTP). High-performance liquid chromatography with electrochemical detection (HPLCED) was used to demonstrate that AMTP depleted serotonin levels, whereas AMT reduced dopamine levels. The host-seeking ability (evaluated with an olfactometer) of Ae. triseriatus was not altered by treatment with either AMT or AMTP. Blood-feeding success was reduced significantly by either oral administration or injection of AMTP. Mosquitoes treated with AMTP responded positively when placed in close proximity to a host (rabbit), but fewer treated than untreated mosquitoes fed to repletion or fed at all. Those feeding to repletion took longer to do so. No differences in feeding ability were observed between control and AMT-treated mosquitoes. These observations indicate that serotonin plays a role in modulating blood-feeding activities of Ae. triseriatus.

A comparison of gas chromatography and high performance liquid chromatography for artemisinin analyses

AbstractAn improved method for high performance liquid chromatography with electrochemical detection (HPLC‐EC) is presented for artemisinin analysis. It involves increased concentration of organic phase, elimination of the degassing step in sample preparation, and reduced time for heating and degassing in mobile phase preparation and recycling. The HPLC‐EC method was compared to a gas chromatographic (GC) method, which measured artemisinin indirectly through two of its degradation products, labelled A and B. Both methods provided a good separation of artemisinin from artemisitene, arteannuin B, and the semisynthetic dihydroartemisinin. Peak B provided a higher correlation to the levels of artemisinin detected by HPLC‐EC. Peaks A, B and Z (a small peak preceding A and B) were identified through electron impact and chemical ionization spectra from GC‐mass spectral analysis.

Acute effects of perinatal hypoxic insult on concentrations of dopamine, serotonin, and metabolites in fetal monkey brain

Seven monkeys (Macaca mulatta) were laparotomized under general anesthesia (halothane, nitrous oxide, oxygen). Fetal hypoxia was induced in four monkeys by occlusion of the umbilical cord with a hydraulic occluder for 5–6 min. Three sham-operated fetuses served as controls. After unclamping, the fetuses were allowed to reperfuse for 20–30 min. To monitor hypoxia, the fetal electrocardiogram was recorded continuously. Hypoxic insult was associated with a decrease in fetal heart rate during the occlusion. After reperfusion, fetuses were immediately sacrificed and neocortex regions dissected on ice, frozen on dry ice and stored at −70°C. Dopamine, 3,4-dihydroxyphenylacetic acid, homovanillic acid, serotonin, and 5-hydroxyindoleacetic acid were assayed by high performance liquid chromatography with electrochemical detection (HPLC/EC) in hippocampus, caudate nucleus and cortical regions. In the hippocampus, there was a significant increase in 5-hydroxyindoleacetic acid concentration. In prefrontal cortex, there was a trend toward an increase in serotonin but no effects on dopamine and homovanillic acid concentrations. Dopamine, serotonin and metabolites were not altered in the caudate nucleus. These data demonstrate that fetal hypoxia followed by reperfusion produced an increase in serotonin concentration measured within the hippocampus and selected cortical areas known to be targets of hypoxic injury.

Bioavailability of Levodopa after Consumption of Vicia faba Seedlings by Parkinsonian Patients and Control Subjects

Recently, we have shown that ingestion of Vicia faba beans improved substantially the clinical features in parkinsonian patients. However, the supply of the beans is season-dependent and their digestion can be quite unpleasant due to flatulence. In the present study, we verified that the L-Dopa content of V. faba seedlings is 20-fold higher than that of the fruit. Moreover, the germination of the seedlings is easy and not season-dependent, and their ingestion does not cause any adverse digestive effects. In the present study, seven Parkinson's disease (PD) patients and nine healthy controls ingested V. faba seedlings. Plasma L-Dopa and dihydroxyphenylacetic acid (DOPAC) levels were measured by a high performance liquid chromatography with electrochemical detection (HPLC-ECD) method. Plasma L-Dopa increased in both populations, and a substantial clinical improvement was observed in the patients according to the Webster scale. Vicia faba seedling ingestion is a useful tool in the treatment of PD patients, especially those in low-income societies where limited resources do not allow the purchase or manufacture of expensive drugs. This treatment might also appeal to those people who prefer natural treatment in PD and in other conditions for which L-Dopa is prescribed.

Chromatographic Analyses of the Effects of Glutathione, Cysteine and Ascorbic Acid on the Monophenol and Diphenol Oxidase Activities of Tyrosinase

Abstract The effects of glutathione, cysteine, and ascorbic acid on the monophenol and diphenol oxidase functions of tyrosinase were assessed by high performance liquid chromatography with electrochemical detection (HPLC-ED) at both oxidative and reductive potentials. The enzyme-catalyzed hydroxylations of tyrosine to dopa and tyramine to dopamine were inhibited completely by glutathione and cysteine, but not by ascorbic acid. However, the rates of oxidation of dopa and dopamine were enhanced approximately 5 % by cysteine and 75 % by glutathione. There was no chromatographic evidence to indicate that either thiol reduced o-quinones back to their respective o-diphenols, a reaction that was documented for ascorbic acid. Glutathione and cysteine each formed sulfnydryl conjugates with the oxidation products of both dopa and dopamine. The thiol-mediated alterations in tyrosinase activity are likely due to the direct interactions of these sulfhydryl compounds with the enzyme, suggesting that the availability an...

Dopamine increase in the prefrontal cortex correlates with reversal of haloperidol-induced catalepsy in rats

The mechanism by which forced swimming reverses haloperidol-induced catalepsy was examined by measuring dopamine (DA) turnover in the nucleus accumbens-ventromedial caudate (NAC-C) and the prefrontal cortex (PFC) in rats. DA and its metabolites 3,4-dihydroxi-phenylacetic acid (DOPAC) and homovanillic acid (HVA) were assessed by microdialysis and high pressure liquid chromatography with electrochemical detection (HPLC-ED) after systemic administration of a cataleptic dose of haloperidol (5 mg/kg) or saline. Haloperidol-induced catalepsy was temporarily suppressed by forced swimming. Haloperidol-treated rats showed an increase of DA, DOPAC, and HVA overflow in the PFC and the NAC-C. This increase was greater in the PFC of rats that were forced to swim. Rats that were not treated with haloperidol but were forced to swim (control group) showed an increase of DA, DOPAC, and HVA in the PFC but not in the NAC-C. Zero micrograms, 5 μg, 10 μg, and 20 μg of DA was bilaterally injected in the PFC of cataleptic rats to evaluate the hypothesis that DA in the PFC reverses catalepsy. Haloperidol-induced catalepsy was diminished by bilateral microinjections of 10 μg and 20 μg but not by 5 μg of DA in the PFC. The higher the dose of DA, the longer the decrease of catalepsy. These results suggest that an increase of DA turnover in the PFC might mediate temporal suppression of haloperidol-induced catalepsy. The mechanism by which the mesocortical DA system reduces catalepsy is discussed.

Antioxidant status and dietary lipid unsaturation modulate oxidative DNA damage

High performance liquid chromatography with electrochemical detection (HPLC-EC) was used to measure 8-hydroxy-2′-deoxyguanosine (8-OHdG), a marker for oxidative DNA damage, in mammary gland isolated from tumor-bearing and tumor-free rats fed diets of varied fatty acid composition and vitamin E and selenium content. A method for tissue preparation and analysis is reported and a significant positive correlation shown between degree of unsaturation of dietary fatty acids and 8-OHdG concentration, regardless of antioxidant status. The increase in 8-OHdG concentration with greater fatty acid unsaturation was more pronounced in the absence of adequate dietary vitamin E and selenium. The implications of these data for defining the role of dietary lipid in the process of mammary carcinogenesis are discussed.

Simultaneous determination of tetrahydrofolate, 10-formyltetrahydrofolate and 5-methyltetrahydrofolate in rat bile by high-performance liquid chromatography with electrochemical detection.

This report describes an analytical method for the measurement of tetrahydrofolate (H4PteGlu), 10-formyltetrahydrofolate (10-HCO-H4PteGlu) and 5-methyltetrahydrofolate (5-CH3-H4-PteGlu) in rat bile by high-performance liquid chromatography with electrochemical detection (HPLC-ECD). After diluting the bile sample with 0.2% sodium ascorbate solution, the sample was analyzed under the following conditions; (a) phenyl bonded phase column as an analytical column; (b) mobile phase consisting of 20 mM acetate buffer (pH 5.0) containing 0.1 mM EDTA; (c) an applied ECD potential of +300 mV; (d) 0.8 ml/min of flow rate. Under the above conditions, peaks of H4PteGlu, 10-HCO-H4PteGlu and 5-CH3-H4PteGlu in rat bile were well separated on the ECD-chromatogram. Detection limits of H4PteGlu, 10-HCO-H4PteGlu and 5-CH3-H4PteGlu were 0.13, 0.11 and 0.10 ng/ml, respectively, at S/N = 3. Bile excretion rates for H4PteGlu, 10-HCO-H4PteGlu and 5-CH3-H4PteGlu, which were analyzed by this method in rats, were 314 +/- 181, 321 +/- 179 and 449 +/- 198 ng/hr, respectively. Bile concentrations of the folates were more than 5,000 times higher than the detection limits for this method. This HPLC-ECD method is, therefore, a useful tool for bile folate analysis.

Relationship of neuroendocrine cells of prostate and serotonin to benign prostatic hyperplasia

Neuroendocrine (NE) cells containing neurosecretory granules, rich in various peptide hormones and biogenic amines such as serotonin (5-HT), are components of the human prostate epithelium. The NE cells probably subserve a paracrine or local regulatory role in both prostatic growth and differentiation as well as the exocrine secretory process. Neuroendocrine cells may be involved in the etiology of benign prostatic hyperplasia (BPH). In this study the number of NE cells in areas of BPH was compared with normal tissue using 5-HT immunocytochemistry. In addition, using high-performance liquid chromatography with electrochemical detection (HPLC-ECD), tissue levels of 5-HT and its metabolite 5-hydroxy-indoleacetic acid (5-HIAA) were analyzed in prostatic tissue extracts including 25 cases of BPH and 16 cases of normal tissue verified by adjacent histologic sections. Compared with normal prostate our results demonstrated a marked decrease in 5-HT immunoreactive NE cells in the vast majority of larger hyperplastic nodules of BPH. These findings were corroborated by quantitative analysis where a significant reduction in the tissue 5-HT levels in BPH (0.539 ± 0.09 SE) compared with normal (1.75 ± 0.22 SE) ( p < 0.05) was found. When smaller nodules of BPH were studied, abundant NE cells, equal or increased in number compared with those in adjacent normal prostatic tissue, were seen. The small apparently developing BPH nodules and ductal-like structures contained NE cells which may be growth foci near the periphery of some hyperplastic nodules. These findings particularly in small hyperplastic nodules suggest that NE cells and their products are involved in controlling cell proliferation through a paracrine hormonal mechanism and may be involved in the pathogenesis of BPH. Serotonin (5-HT) and NE peptides may represent that elusive local “missing link” often alluded to in various theories relating to the development of early nodular hyperplasia in BPH.

2-Oxo-histidine as a novel biological marker for oxidatively modified proteins

We report a promising finding that oxidative modification of proteins by free radicals could be monitored by the formation of oxidized histidine that is detectable by reverse-phase HPLC with electrochemical detection (HPLC-ECD). When the N-protected histidine derivative ( N-benzoyl-histidine) was exposed to a free radical-generating system (copper/ascorbate), a number of products were detected by HPLC-ECD and the main product among them was found to be identical to N-benzoyl-2-oxo-histidine. The acid hydrolysis of N-benzoyl-2-oxo-histidine provided a single product (2-oxo-histidine) that was detected sensitively by HPLC-ECD. Thus 2-oxo-histidine was indeed generated as the main product in the oxidatively modified proteins by free radicals. Taken together, 2-oxo-histidine may be a useful biological marker for assessing protein modifications under oxidative stress.

Effects of calcitonin on CNS monoamines following carrageenan-induced inflammation in rats

The present study examined the effects of systematically administered calcitonin (CT, 10 IU/0.25 ml, SC) on changes in CNS monoamines (MAs) following unilateral carrageenan (CARRA)-induced inflammation in the rat hindpaw. High-performance liquid chromatography with electrochemical detection (HPLC-EC) for MAs was performed on the whole brain and rostral spinal cord. Carrageenan-evoked inflammation significantly increased brain serotonin [5-hydroxytryptamine (5-HT)], norepinephrine (NE), and dopamine (DA) levels. CT significantly reduced these CARRA-induced elevations in brain MAs. Elevated spinal cord 5-HT and NE levels were observed in CARRA-treated animals. CT administration increased 5-HT and NE in both the CARRA-treated animals and their saline controls. Spinal cord DA levels were not affected by either CARRA or CT administration. These findings suggest the involvement of CNS monoaminergic substrates in CT-induced hypoalgesia in inflammatory nociception.