Effects of L-dopa on putrescine levels in the brain and the liver of the rat.

The pharmacological effects of several amino acid precursors of putative neurotransmitters on putrescine levels in the brain and the liver of the rat were studied. L-dopa increased brain and liver putrescine levels in a dose-dependent manner that reached its maximum effect in 4-6 h. The increase in liver putrescine was associated with a concomitant increase in ornithine decarboxylase activity. L-5-hydroxytryptophan increased liver putrescine but had no effect on brain putrescine levels. D-DOPA and D-5-hydroxytryptophan were both ineffective in altering brain or liver putrescine. The effects of L-DOPA persisted after hypophysectomy and were not associated with changes in tissue levels of S-adenosylmethionine. The repeated administration of L-DOPA for periods of 48 and 96 h resulted in a sustained elevation of putrescine levels in the brain but not in the liver.     

Effects of amphetamine,methylphenidate, and apomorphine on regional brain serotonin and 5-hydroxyindole acetic acid

Electrophysiological and cytofluorometric data suggest that doses of amphetamine which enhance locomotor activity and promote focused stereotypies produce pronounced effects on serotonin pathways in the CNS. However, the biochemical evidence regarding changes in serotonergic function produced by moderate doses of this drug is inconsistent. Therefore, the present study was designed to further examine the effects of amphetamine (1–5 mg/kg) on regional brain serotonin and its metabolite and to compare these effects to behaviorally comparable doses of methylphenidate and apomorphine. At doses which produce a multiphasic behavioral response pattern, including a stereotypy phase consisting primarily of repetitive head movements and occasional oral stereotypies, amphetamine (3 mg/kg) and methylphenidate (30 mg/kg) increased levels of 5HIAA in striatum and frontal cortex, two brain regions which receive serotonergic projections from the dorsal raphe nucleus. In contrast, these drugs decreased or had no effect on 5HIAA levels in hippocampus, a brain region which receives its serotonergic innervation from the median raphe nucleus. A moderate dose of apomorphine (0.5 mg/kg) produced a comparable pattern of neurochemical effects. These data are consistent with electrophysiological and cytofluorometric data suggesting enhanced dorsal raphe serotonergic function following amphetamine-like stimulants. Pretreatment of animals with -methyltyrosine at a dose sufficient to prevent the locomotor stimulation and stereotypy promoted by amphetamine, or by haloperidol, failed to prevent the amphetamine-induced increase in 5HIAA, indicating that these serotonergic effects are not secondary to the amphetamine facilitation of dopaminergic transmission. The results of this study suggest that serotonin may play a modulatory role in the behavioral effects of amphetamine-like stimulants which is dependent for its expression on an intact dopamine system.Abbreviations DA dopamine - AMPH S(+)amphetamine - 5HT serotonin - MP methylphenidate - APO apomorphine - 5HIAA 5-hydroxyindoleacetic acid - MT -methyltyrosine - DOPAC 3,4-dihydroxyphenylacetic acid - HVA homovanillic acid - HAL haloperidol     

Influence of l-3-methoxytyrosine on monoamine synthesis in rat brain

Summary Rats were injected i.p. with l-3-methoxytyrosine, 100 or 300 mg/kg. One h later brain, liver, heart and blood plama were analyzed for catecholamines and their precursors. In brain Dopa as well as dopamine and noradrenaline levels were unchanged, while demethylation of l-3-methoxytyrosine might have occurred in peripheral organs since Dopa levels in liver and dopamine in heart were elevated. 3-Methoxytyramine could not be detected in brain and liver after treatment with l-3-methoxytyrosine.Monoamine synthesis in vivo was measured in whole brain by determining the accumulation of Dopa and 5-hydroxytryptophan 30 min after the i.p. injection of NSD 1015 (3-hydroxybenzylhydrazine HCl, 100 mg/kg), an inhibitor of the aromatic amino acid decarboxylase. l-3-Methoxytyrosine attenuated the formation of Dopa and 5-hydroxytryptophan by about 25% in brain tissue. The effect was paralleled by a decrease in the brain concentration of tryptophan.     

L-2-(N-叔丁氧酰基)-3′,4′-二甲氧基苯丙氨酸乙酯的合成

目的：改进L-2-（N-叔丁氧酰基）-3′,4′-二甲氧基苯丙氨酸乙酯的合成工艺。方法：以左旋多巴为起始原料,采用“半分离纯化”的制备方法进行合成,并对处理工艺进行优化。结果：通过此法制备步骤简单,后处理容易,可有效减少原料及中间体的氧化程度。总收率达到45．4％。结论：这是一种易于操作、适合规模化生产的制备工艺。     

Ligand-Based Design, Synthesis, and Pharmacological Evaluation of 3-Methoxyquinoxalin-2-carboxamides as Structurally Novel Serotonin Type-3 Receptor Antagonists

Employing a ligand-based approach, 3-methoxyquinoxalin-2-carboxamides were designed as serotonin type-3 (5-HT(3) ) receptor antagonists and synthesized from the starting material o-phenylenediamine in a sequence of reactions. The structures of the synthesized compounds were confirmed by spectral data. These carboxamides were investigated for their 5-HT(3) receptor antagonisms in longitudinal muscle myenteric plexus preparations from guinea-pig ileum against a standard 5-HT(3) agonist, 2-methy-5-HT, and their antagonism activities are expressed as pA(2) values. Compounds 6a (pA(2) : 7.2), 6e (pA(2) : 7.0), 6f (pA(2) : 7.5), 6g (pA(2) : 7.5), 6n (pA(2) : 7.0), and 6o (pA(2) : 7.2) exhibited antagonism greater than that of the standard 5-HT(3) antagonist, ondansetron (pA(2) : 6.9).     

Effects of PCPA on the consumption of alcohol, water and other solutions.

The influence of para-chlorophenylalanine (PCPA) on the preference for alcohol, saccharin, glucose, and sodium chloride solutions and on water intake was studied in rats. Ten daily intragastric doses of 100 mg/kg PCPA were found to reduce alcohol preference both during and after PCPA treatment. Administration of daily 20 mg/kg IP doses of 5-hydroxtryptophan (5-HTP), plus a peripheral decarboxylase inhibitor, failed to reverse the PCPA-induced suppression in the post-PCPA test. Alcohol preference was not reduced below baseline following PCPA if this drug was administered between preference tests rater than coincident with alcohol drinking. Preference for saccharin, glucose, and sodium chloride solutions were all affected by PCPA. Large increases in water intake were produced by 50, 100, or 200 mg/kg PCPA given orally for 10 days. These experiments suggest that alcohol preference, in studies where PCPA treatment and alcohol drinking occur concurrently, may be considerably influenced by learned aversions to alcohol. Also, PCPA may, under some circumstances, produce an increased consumption of water by rats.     

Effect of clonidine on the 5-hydroxytryptamine and 5-hydroxyindoleacetic acid brain levels

The effects of clonidine on the brain levels of 5-HT and 5-HIAA in rats and mice were studied. Clonidine did not change the levels of 5-HT and 5-HIAA in the whole brains of either animal species but the 5-HT concentrations were elevated in rat brain pons + medulla oblongata. Clonidine antagonized the increase in the brain 5-HIAA levels induced by apomorphine in rats and mice. The decrease in the 5-HT level and the increase in the 5-HIAA level observed in rats after L-dopa (given with peripheral decarboxylase inhibitor RO 4-4602) were counteracted by clonidine.     

Activation of tryptophan hydroxylase from slices of rat brain stem incubated with agents which promote calcium uptake or intraneuronal release.

Incubation of slices of rat brain stem under conditions that promote calcium accumulation by nerve tissue (Na-free medium, ouabain. A23187) or intraneuronal release of calcium from mitochondrial stores (metabolic inhibitors, cyanide, azide, rotenone, guanidine and dicoumarol) has been found to result in an increase in the activity of tryptophan hydroxylase, prepared from the slice preparations in a low speed supernatant fraction and assayed in the presence of 200 μM L-tryptophan and 50 μM DL-6-methyl-5,6,7,8-tetrahydropterin (6-MPH₄). The increase in enzyme activity following treatment of the slices with Na⁺-free medium, ouabain, ionophore A23187, guanidine, cyanide or azide was reflected in altered kinetic properties of the enzyme, namely a decrease in the K_m of the enzyme for both substrate and artificial reduced pterin cofactor. In addition, a modest increase in V_max was observed, but was not always statistically significant. The alterations in kinetic properties obtained following the different treatments to the slice preparations were similar to those obtained with enzyme prepared from brain stem slices depolarized in a potassium-enriched incubation medium. This depolarization-induced activation of tryptophan hydroxylase is a calcium-dependent phenomenon. In agreement with this, no increase in enzyme activity was observed when calcium ions were omitted from the Na⁺-free medium and media containing ouabain or A23187. Removal of external calcium did not abolish the increase in enzyme activity obtained with metabolic inhibitors, presumably because these substances release calcium from mitochondria. The data are consistent with the view that a rise in free intraneuronal calcium triggers certain biochemical events which activate tryptophan hydroxylase.     

Simultaneous determination of femtomole quantities of 5-hydroxytryptophan, serotonin and 5-hydroxyindoleacetic acid in brain using HPLC with electrochemical detection

A simple rapid method for the determination of 5-hydroxytryptophan, serotonin (5-hydroxytryptamine), and 5-hydroxyindoleacetic acid in brain is presented. Brain proteins are precipitated with Zn(OH)2. The indoles in the supernatant are separated by HPLC in less than than 8 min on a reverse phase column and detected electrochemically. As little as 38 fmol of hydroxyindole compound can be detected and quantitated. Because the method is rapid and uncomplicated many samples can be processed in a day.     

Changes of acetylcholine, catecholamines and amino acid in mice brain following treatment with Nuvacron and Furadan

The effects of multiple intraperitoneal doses of Nuvacron (0.8 mg/kg) or Furadan (0.25 mg/kg) on the concentrations of brain neurotransmitters in mice were studied. The following were measured: acetylcholine, acetylcholinesterase, gamma-aminobutyric acid, epinephrine, norepinephrine, dopamine and 5-hydroxytryptamine. These pesticides caused a significant decrease in acetylcholinesterase activity and a significant increase in acetylcholine, gamma-amino-butyric acid, epinephrine, norepinephrine, dopamine and 5-hydroxy tryptamine concentrations. The increased concentrations of the neurotransmitters in mouse brain might be associated with CNS depressant action induced by the insecticides.     

The effect of alcoholism on salsolinol and biogenic amines in human brain

Chronic alcoholics with a well documented history of alcohol abuse were divided at autopsy into two groups, intoxicated alcoholics (IA, with blood ethanol levels) and sober alcoholics (SA, without blood ethanol levels). Norepinephrine (NE), 4-hydroxy-3-methoxyphenyl-glycol (HMPG), 5-hydroxyindoleacetic acid (5-HIAA), dopamine (DA), salsolinol (SAL) and methylated salsolinol (M-SAL) in caudate nucleus and putamen from the two groups of alcoholics and an age-matched control group were analysed with gas chromatography-mass spectrometry. HMPG was significantly increased in the brains of the alcoholics compared to controls (IA, P less than 0.001 and SA, P less than 0.05) indicating an increased NE turnover in the brains of alcoholics. 5-HIAA, the major 5-hydroxytryptophan (5-HT) metabolite, was increased in the caudate nucleus from SA (P less than 0.05) compared to controls and IA. This could be interpreted as an increased turnover of 5-HT at abstinence. SAL can be formed from DA and acetaldehyde and/or pyruvate. SAL was found in all brains studied. The levels were about 1% of the dopamine concentrations. SAL had a tendency to be increased in brains of IA compared to control brains. The most remarkable finding was that SAL was significantly decreased in both the caudate nucleus and putamen from SA compared to controls and IA. M-SAL showed tendencies in the same directions as SAL. DA did not show any significant changes, but tended to be lower in SA.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of acute and chronic tramadol on [3H]-5-HT uptake in rat cortical synaptosomes

1. Tramadol hydrochloride is a centrally acting opioid analgesic, the efficacy and potency of which is only five to ten times lower than that of morphine. Opioid, as well as non-opioid mechanisms, may participate in the analgesic activity of tramadol.
2. [³H]-5-hydroxytryptamine (5-HT) uptake in rat isolated cortical synaptosomes was studied in the presence of tramadol, desipramine, fluoxetine, methadone and morphine. Methadone and tramadol inhibited synaptosomal [³H]-5-HT uptake with apparent K_is of 0.27±0.04 and 0.76±0.04 μM, respectively. Morphine essentially failed to inhibit [³H]-5-HT uptake (K_i 0.50±0.30 M).
3. Methadone, morphine and tramadol were active in the hot plate test with ED₅₀s of 3.5, 4.3 and 31 mg kg⁻¹, respectively. At the highest tested dose (80 mg kg⁻¹) tramadol produced only 77±5.3% of the maximal possible effect.
4. When [³H]-5-HT uptake was examined in synaptosomes prepared from rats 30 min after a single dose of morphine, methadone or tramadol, only tramadol (31 mg kg⁻¹, s.c., equal to the ED₅₀ in the hot plate test) and methadone (35 mg kg⁻¹, s.c., equal to the ED₉₀ in the hot plate test) decreased uptake.
5. Animals were chronically treated for 15 days with increasing doses of tramadol or methadone (5 to 40 mg kg⁻¹ and 15 to 120 mg kg⁻¹, s.c., respectively). Twenty-four hours after the last drug injection, a challenge dose of methadone (35 mg kg⁻¹, s.c.) or tramadol (31 mg kg⁻¹, s.c.) was administered. [³H]-5-HT uptake was not affected in synaptosomes prepared from rats chronically-treated with methadone, whereas chronic tramadol was still able to reduce this parameter by 42%.
6. Rats chronically-treated with methadone showed a significant increase in [³H]-5-HT uptake (190%) 72 h after drug withdrawal. In contrast, [³H]-5-HT uptake in rats chronically-treated with tramadol (110%) did not differ significantly from control animals.
7. These results further support the hypothesis that [³H]-5-HT uptake inhibition may contribute to the antinociceptive effects of tramadol. The lack of tolerance development of [³H]-5-HT uptake, together with the absence of behavioural alterations after chronic tramadol treatment, suggest that tramadol has an advantage over classical opioids in the treatment of pain disorders.

     

The 4-O-methyl metabolites of catecholamines. Homo-iso-vanillin acid in rat urine and brain; urinary iso-vanyl compounds after intraperitoneal administration of dopamine and of dopamine precursors and derivatives

Homo-iso-vanillic acid (3-hydroxy, 4-methoxyphenylacetic acid, iso-HVA was detected in rat urine and brain, with a molar ratio of iso-HVA to HVA of 0·07 in urine and about 0·35 in brain. The free urinary iso-vanyl and vanyl phenolcarboxylic acids were studied after intraperitoneal loads with the following compounds: l-dopa, $\text{l}\text{-3-O-}\text{methyldopa}\text{,}\text{l}\text{-4-O-}\text{methyldopa}$, dopamine, 3-O-methyldopamine, 4-O-methyldopamine and 3,4-dihydroxyphenylacetic acid. The results suggest the following conclusions. (1) The molar ratio iso-HVA/HVA is not constant. After dopa as well as dopamine loads it rises with the increase of the dose of precursor administered, showing that, in vivo, the 4-O-methylation process depends, to some extent, on the substrate concentration. (2) In contrast with the other catechols (dopamine and 3,4-dihydroxyphenylacetic acid), l-dopa itself does not seem to be para-O-methylated. It is therefore unlikely that 4-O-methyldopa would be a metabolite of l-dopa in vivo. (3) Distinct urinary metabolites from $\text{l}\text{-3-O-}\text{methyldopa}$ (vanylmandelic and vanillic acids) on one hand and from l-4-O-methyldopa (unknown iso-vanyl phenolcarboxylic acid) on the other, support evidence that some of the metabolic transformations of the side-chain of the O-methyl-catecholamines are different according to whether the methyl group is bound on the meta or on the para position. (4) The high level of cerebral iso-HVA might be due to either a lower iso-HVA than HVA transport outside the brain, or to the existence, in addition to the dopamine source, of a second cerebral metabolic pathway for the production of iso-HVA.     

N-methylation of biogenic amines. I. Characterization and properties of an N-methyltransferase in rat brain using 5-methyltetrahydrofolic acid as the methyl donor

Some properties and kinetics of a recently identified brain N-methyltransferase requiring 5-methyltetrahydrofolic acid as the methyl donor are described in this paper. In addition to the assay using dopamine as substrate, the more stable substrate, 3-hydroxy-4-methoxyphenethylamine with a rapid extraction procedure was also used. The pH optimum of the enzyme, about pH 6·4, was found to differ from that previously found with dopamine in the presence of metabisulfite. The reaction products were identified by column and thin layer chromatography and indirectly by testing various N-methyl-, dimethyl- and dimethoxy-derivatives of dopamine for their ability to be N-methylated. The reaction was a linear function of time and enzyme concentration. The K_m for 5-methyltetrahydrofolic acid was 2.5 × 10^?5 M. The kinetic experiments to determine the K_m for dopamine and 3-hydroxy-4-methoxyphenethylamine showed an anomalous behaviour of the saturation curve. When the results were plotted S/v vs S, a non-linear curve was obtained suggesting that the enzyme was behaving as an allosteric protein. Although further kinetic experiments are needed to confirm these results, a possible regulatory function can be postulated for this enzyme. In. addition to dopamine and its derivatives, amines such as tryptamine, serotonin and amphetamine were also N-methylated under the same conditions.     

An autoradiographic study of dextromethorphan high-affinity binding sites in rat brain: sodium-dependency and colocalization with paroxetine

1. The distribution and some pharmacological properties of centrally located dextromethorphan high-affinity binding sites were investigated by in vitro autoradiography.
2. Sodium chloride (50 mM) induced a 7 to 12 fold increase in dextromethorphan binding to rat brain in all areas tested. The effect of sodium was concentration-dependent with a higher dose (120 mM) exerting a smaller effect on binding.
3. [³H]-dextromethorphan binding in the presence of sodium was inhibited in the presence of the anticonvulsant phenytoin at a concentration of 100 μM, while the σ ligand (+)-3-(-3-hydroxyphenyl)-N-(1-propyl)pipendine ((+)-PPP) had no effect on the binding, suggesting an interaction with the DM₂ site.
4. The distribution of the sodium-dependent binding identified in this study correlated significantly with the distribution of the selective 5-HT uptake inhibitor [³H]-paroxetine, and paroxetine and dextromethorphan mutually displaced their binding at concentrations in the low nanomolar range.
5. These data show that dextromethorphan and paroxetine share a sodium-dependent high affinity binding site in rat brain, and suggest that dextromethorphan might interact, in the presence of sodium, with the 5-HT uptake mechanism in rat brain.

     

Effects of N,N-dimethyltryptamine (DMT) and 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) on shock elicited fighting in rats.

Rats were tested for shock elicited fighting under various doses of N,N-dimethyltryptamine (0.12, 0.25, 0.50, 1.0, 4.0, 8.0 mg/kg) and 5-methoxy-N,N-dimethyltryptamine (0.06, 0.12, 0.5, 2.0 mg/kg). Both drugs produced an inhibition of fighting at higher doses but no significant effects at lower doses. The effects of these drugs on shock elicited fighting, as well as on other behaviors, thus differ from those of another indole hallucinogen, d-lysergic acid diethylamide, and are discussed in relation to their effects on single unit activity of the raphe-serotonin system and their interaction with other neurotransmitter systems.     

Association of altered brain norephinephrine and serotonin with the obesity induced by goldthioglucose in mice.

Two experiments examined the possibility that mice rendered obese by systemic injection of goldthioglucose (GTG) possess altered endogenous levels of brain norepinephrine (NE), dopamine (DA), serotonin (5-hydroxytryptamine or 5HT) and/or 5-hydroxyindoleacetic acid (5HIAA). In the first experiment, single-housed GTG-obese mice were found to have normal brain DA and 5HIAA but 14% less NE and 6% less 5HT than controls. This neurochemical profile was strikingly similar to that previously reported for rats rendered obese by ventromedial hypothalamic lesions (i.e., normal DA and 5HIAA, 19% less NE, 7% less 5HT). However, in the second experiment, equally obese GTG mice pair-housed with non-obese controls showed normal DA, 5HIAA, and NE but 9% more 5HT than controls. In other words, absolute levels of these brain substances were inconsistent with respect to obesity across experiments. On the other hand, when ratios of all possible combinations of these compounds were compared across experiments, only 5HT/NE ratios were consistently different (higher) in GTG mice. In addition, reliable inverse correlations were obtained between weight gain parameters and brain 5HT/NE or 5HIAA/NE ratios for GTG mice. These findings suggest that interactions between brain 5HT and NE neurons may contribute to the overeating and obesity which occur in mice after GTG administration.     

Further studies on the role of calcium in the depolarization-induced activation of tryptophan hydroxylase: Effect of verapamil,tetracaine, haloperidol and fluphenazine

Tryptophan hydroxylase becomes activated by a calcium-dependent process following depolarization of slices of rat brain stem in a potassium-enriched medium. The present study shows that the mechanism responsible for raising enzyme activity is sensitive to increasing concentrations of calcium in the depolarizing medium. Enzyme activity increased progressively as the calcium concentration in the medium was raised from 0.1 to 5.0 mM. The depolarization-induced activation was fully reversible and could be blocked by verapamil, a calcium channel blocking agent, tetracaine, a local anesthetic, and two antipsychotic drugs, haloperidol and fluphenazine, which bind calmodulin. Unlike verapamil and tetracaine, the antipsychotics appeared to have an intracellular site of action, for they blocked the increase in enzyme activity induced when brain stem slices were incubated in a calcium-free medium in the presence of a metabolic inhibitor, such as guanidine. This activation is presumed to be due to the increase in intracellular free calcium that occurs in the presence of such poisons. The inhibitory effects of haloperidol and fluphenazine on the depolarization-induced activation of tryptophan hydroxylase, taken together with published evidence that supernatant preparations of the enzyme are activated when incubated under phosphorylating conditions by a calcium-calmodulin-dependent process, suggest that calmodulin may mediate the calcium-dependent activation induced by depolarization.     

3H-imipramine high-affinity binding sites in rat brain. Effects of imipramine and lithium

The specific high-affinity binding of ³H-imipramine to rat brain membranes was investigated. Five weeks of lithium treatment decreased the number of binding sites, but had no effect on the affinity constants. Long-term imipramine treatment had no effect on the number of binding sites but apparently decreased the affinity. The latter effect was probably due to imipramine remaining in the membrane preparation.