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Influence of a prolonged treatment with disulfiram and D(-)penicillamine on nitrosodiethylamine-induced biological and biochemical effects in rats. I. Investigations on the drug metabolizing system.

The influence of a prolonged treatment with disulfiram (DSF) and D(-)penicillamine (PA) on biological and biochemical effects induced by nitrosodiethylamine (NDEA) was studied in rats. The combination of NDEA and DSF led to a massive and early development of esophageal tumors, which were fatal to the animals. No liver tumors were observed in this group, whereas PA in combination with NDEA led to an increased development of liver tumors compared with NDEA alone. In the last two groups, only incidental tumors of the esophagus were observed. Nasal cavity tumors also appeared earlier in the animals treated with DSF and NDEA than in animals treated with NDEA alone or with NDEA plus PA. At a biochemical level, DSF led to a significant inhibition of hepatic anilinehydroxylase and nitroso-dimethylaminedemethylase in contrast to PA, which had no influence on these enzymes. The reduced activities of these drug-metabolizing enzymes did not appear to be related to gross cytochrome P450 content. Highly significant increases in glutathione content and glutathione-S-transferase activity (GSH/GST) were induced by DSF but not by PA. Because N-nitrosodiethylamine requires enzymatic activation to form the ultimate carcinogen, it is suggested that the observed inhibition of nitrosamine-transforming enzymes in the liver during DSF treatment leads to an increased amount of intact nitrosamines in other organs, e.g., in the esophagus, where it could be transformed to the ultimate carcinogen. DSF treatment alone or in combination with NDEA leads to an accumulation of trace elements in the liver, whereas PA eliminated copper and cobalt. The possible influence of these elements on tumor development is discussed in part II of this study.

Animals↗

Influence of a prolonged treatment with disulfiram and D-penicillamine on nitrosodiethylamine-induced biological and biochemical effects. II. Investigations on trace elements in the liver.

The influence of a 28-week treatment with disulfiram (DSF), D-penicillamine (PA), and nitrosodiethylamine (NDEA), as well as with a combination of DSF or PA with NDEA on the concentrations of eight essential trace elements in the whole liver tissue of rats was measured by means of neutron activation analysis. While NDEA treatment lowered the Zn content of the liver, DSF alone or in combination with NDEA enhanced the Zn and Se concentration by 50%-80%. Co, Cu, and Cd levels were increased by factors of 10, 60, and 110, respectively. The Mo concentration was decreased by 50% after DSF administration. PA reduced Cu, Co, and Zn in the liver. PA/NDEA treatment also lowered Cu, Co, and Zn content, but there was no strengthening effect of PA on the decrease in Zn observed with NDEA. The change of trace element concentrations, especially of Cu, is discussed with regard to the observed tumor induction in the liver, which tended to be increased by a combined NDEA/PA administration compared with NDEA treatment alone, whereas a protective action of DSF against NDEA induced liver tumors could not be established.

Animals↗

Disulfiram augments oxidative stress in rat brain following bilateral carotid artery occlusion.

We examined the brain oxidative stress which accompanies 30 min of bilateral carotid artery ligation (BCAL) in terms of changes in brain levels of glutathione; reduced (GSH) and oxidized (GSSG) forms and the exacerbation of oxidative stress by disulfiram (DSF). These results indicate that BCAL alone decreases GSH content and limits glutathione reductase (GR) activity, and these changes were enhanced by DSF pretreatment. Similar observations were recorded with DSF alone. GR activity (74.3 +/- 4.0 micromol min(-1) mg(-1) tissue; p < 0.001) and GSH content (1.23 +/- 0.06 micromol min(-1) g(-1) tissue; p < 0.001) was attenuated in rats subjected to synergistic effect of BCAL and DSF with a concomitant increase of GSSG (0.006 +/- 0.006 micromol min(-1) g(-1) tissue; p < 0.001). Recovery of GSH/GSSG level and GR activity during reperfusion following 30 min BCAL was considerably delayed (96 h) in the BCAL and DSF group as compared to the recovery time of 24 h in the group subjected to BCAL-reperfusion alone. Perturbation of GSH/GSSG homeostasis as a result of BCAL was augmented by DSF. These findings clearly demonstrate central nervous system oxidative stress due to a BCAL-DSF synergistic effect. Based on the results obtained with this model, we conclude that DSF increases brain oxidative stress and this may be detrimental to alcoholics who might drink and develop an acetaldehyde-induced hypotension while taking DSF.

Animals↗

Elemental alterations during the exposure of 1,2-dichloroethane (EDC), disulfiram (DSF), and EDC-DSF to male Sprague-Dawley rats.

Trace elements participate in the organ specific impact of 1,2-dichloroethane (EDC) and Disulfiram (tetraethylthiuram disulfide; Antabuse (DSF] administered singly or together, on male Sprague-Dawley rats exposed by diet (AIN-76) to DSF (0 and 0.15% for 10 d before and during exposure to EDC) and by inhalation to EDC (0, 153, 304, 455 ppm (v/v); 7 h/d for 5 d/wk for 30 exposure days). Kidney, liver, spleen, and testes at exposure d 30 as well as progressive urine samples were examined for elemental content by simultaneous inductively coupled plasma atomic emission spectroscopy. Each compound singly or together produced EDC dose related (r greater than or equal to 0.8) changes in metal content in organs relative to controls. There were increases induced by EDC alone for P and Sr in the liver and decreases for Fe, Mg, and P in the spleen. EDC in DSF-exposed animals caused increases in Ca, Cu, Fe, Mn, and S and a decrease in K in the liver; increases in Ca, Cu, Fe, Mn, Mo, P, and S and a decrease of Zn in the testes; an increase in Fe and a decrease in K in the spleen; and an increase of P in the kidney. DSF alone increased Cu in the liver but decreased it in the testes and kidney; Pb was increased in the liver and kidney and Zn in the liver, spleen, and kidney; Al and Si were increased also in the liver, S in the spleen, and K in the kidney; Mn and Na were decreased in the kidney. The organs showing histopathology (the liver and testes) both showed increases in Ca, Cu, Fe, Mn, and S. Metals in urine characterized a "shock" impact of the initial exposure by initial excretion of Na and retention of most other elements. After steady state (greater than 12 d), EDC alone caused increases for Sr and Zn; for EDC-DSF, EDC also decreased Na in addition to the changes elicited by DSF alone (increases in S and Zn and a decrease for Cu). The results were interpreted from the perspective of the effects of metals on the glutathione detoxicative pathway, the concentration of free diethyldithiocarbamate in urine, and an interaction with bone. Mechanisms of action of EDC, DSF, and EDC-DSF must include consideration of trace elements in addition to organic intermediates, metabolites, and enzymes.

Animals↗

Effects of disulfiram on mixed function oxidase system and trace element concentration in the liver of rats.

Disulfiram (DSF), an inhibitor of chemically induced carcinogenesis, and its metabolite diethyldithiocarbamate (DDTC) have been investigated for their influence on trace element distribution and on certain enzymes of the drug metabolizing system in the livers of phenobarbital (PB) treated rats. Both substances diminished the PB induced enzyme response in liver microsomes, DDTC being more effective (-85%) than DSF (-60%). The copper, cobalt and zinc content of the livers of DSF treated animals were increased by factors of 6, 3 and 1.5 respectively as compared to controls, while DDTC treatment had no influence on liver trace element content. A correlation between enzyme inhibition and enhanced trace element uptake of the liver after DSF administration could not be observed. The change of trace element transport into the liver during DSF treatment is discussed.

Animals↗

Acute effects of the aldehyde dehydrogenase inhibitors, disulfiram, pargyline and cyanamide, on circulating ketone body levels in the rat.

Acetonemia is generally associated with the ketogenic states of fasting and diabetes. Disulfiram (DS), an inhibitor of aldehyde dehydrogenase (AlDH) that is used as an alcohol deterrent drug, is also known to elevate blood acetone in humans, but in the absence of a commensurate increase in its metabolic precursor, acetoacetate. We reexamined the effects of DS and other AlDH inhibitors on circulating ketone body levels in male rats of Sprague-Dawley descent and again demonstrated a 6- and 16-fold increase in blood acetone along with normal levels of acetoacetate at 6 and 24 hr after DS. Pargyline, another inhibitor of AlDH, maintained normal blood acetone levels in the presence of reduced acetoacetate levels. A third inhibitor of AlDH, cyanamide, administered to fasted and nonfasted rats, elevated blood acetone levels 10-fold over controls, with, however, a commensurate 5- and 7-fold increase in blood acetoacetate levels. The threshold values for the cyanamide-induced elevation of blood acetone and acetoacetate were equivalent, i.e. approximately 0.25 mmol/kg body weight (i.p.). The elevation of acetoacetate and the inhibition of hepatic catalase activity by cyanamide are not mechanistically linked, since 3-amino-1,2,4-triazole, another inhibitor of catalase, elevated blood acetone but not acetoacetate levels. These findings suggest that DS-induced acetonemia is due to inhibition of acetone metabolism, whereas enhanced acetone formation through acetoacetate contributes significantly to cyanamide-induced acetonemia.

3-Hydroxybutyric Acid↗

Diethylthiocarbamic acid methyl ester. A potent inhibitor of aldehyde dehydrogenase found in rats treated with disulfiram or diethyldithiocarbamic acid methyl ester.

Rats were treated with disulfiram (Antabuse, DSF) or its metabolite diethyldithiocarbamic acid methyl ester (Me-DDC) and challenged with ethanol. The blood pressure response to ethanol was followed and blood was analyzed for DSF, Me-DDC and diethyldithiocarbamic acid (DDC). The rat liver aldehyde dehydrogenase (ALDH) isozyme activities were measured 2 hr after the ethanol challenge. Both treatments produced a significant fall in the blood pressure when challenged with ethanol, probably caused by a marked decrease in hepatocyte low Km and high Km activities. The mean plasma concentration ranges of Me-DDC and DDC were found to be 49-1241 nmol/l and 182-841 nmol/l, respectively, whereas DSF was undetectable. In addition, it was found that inactivation of hepatocyte low Km ALDH activity was dependent on preoxidation of Me-DDC by the microsomal cytochrome P-450 mixed function oxidases. Me-DDC was found to be oxidized under aerobic conditions in the presence of NADP to form diethylthiocarbamic acid methyl ester (Me-DTC). The structure was confirmed from its MS/EI fragmentation spectrum. Me-DTC was found to be a potent inhibitor of low Km ALDH when added to rat liver homogenate. The compound was also identified as a metabolite in rat blood collected from the DSF and Me-DDC treated rats, and in blood from human alcoholics on DSF treatment. Me-DTC appears to be more selective for the low Km isozymes whereas the opposite seems to be the case for the hydrolytic product, DTC.

Aldehyde Dehydrogenase↗

Regulation of cytochrome P450 2B1/2 genes by diallyl sulfone, disulfiram, and other organosulfur compounds in primary cultures of rat hepatocytes.

Our previous study demonstrated that diallyl sulfide (DAS), a compound derived from garlic, transcriptionally activated the P450 2B1/2 genes in rat liver. In the present study, rat primary hepatocytes were used to determine the effects of DAS and its metabolite, diallyl sulfone (DASO2), on the expression of the P450 2B1/2 genes. Freshly isolated adult rat hepatocytes were cultured in a serum-free medium on a reconstituted basement membrane matrix "matrigel" that enabled the hepatocytes to maintain expression of numerous liver-specific genes for more than 1 week. After 48-hr of acclimation, 0.1, 0.5, and 2.0 mM concentrations of DAS or DASO2 were added to the culture medium and the cells were harvested at 4, 12, 24, or 36 hr after the treatment for the preparation of microsomes and RNA. Cytotoxicity was not observed by morphological examinations after DAS and DASO2 treatments. In contrast to the in vivo results, there was only a slight increase in the levels of P450 2B1/2 mRNA and protein in DAS-treated cells. However, DASO2 treatment (2 mM) resulted in 11-, 21-, and 22-fold increases in P450 2B1/2 mRNA levels at 12, 24, and 36 hr after the treatment, respectively. P450 2B1/2 protein levels were also increased markedly in DASO2-treated cells. Co-incubation of the rat hepatocyte cultures with a physiological concentration of growth hormone significantly blocked the induction of P450 2B1/2 mRNA by DASO2. Northern blot analysis using oligonucleotide probes specific for 2B1 and 2B2 demonstrated that DASO2 induced mRNA levels of both 2B1 and 2B2, with a greater induction of 2B1 mRNA. For comparison, the effects of disulfiram (DSF) and its metabolite, diethyldithiocarbamate (DDTC), on P450 2B1/2 mRNA expression were also examined in the cultured rat hepatocytes. Both DSF and DDTC caused a significant increase in P450 2B1/2 mRNA level with the highest induction at 0.5 mM. Addition of growth hormone to the culture effectively suppressed the P450 2B1/2 mRNA induction by DSF but had little effect on the induction by DDTC. Neither mRNA nor protein levels of P450 2E1 in cultured hepatocytes were affected by all the organosulfur compounds tested. These results suggest that DASO2, DSF and DDTC selectively modulate P450 isozymes in cultured rat primary hepatocytes and that the induction of P450 2B1/2 by DAS in rat liver may be mediated by its metabolite, DASO2.

Allyl Compounds↗

In vitro inhibition of rat and human glutathione S-transferase isoenzymes by disulfiram and diethyldithiocarbamate.

The drug disulfiram (DSF, Antabuse) has been used in the therapy of alcohol abuse. It is a potent inhibitor of aldehyde dehydrogenase. Its reduced form, diethyldithiocarbamate (DDTC), and further metabolites show similar activities. DSF and DDTC have also been widely used to inhibit mixed-function oxidases. In this study, the reversible inhibition and time-dependent inactivation of the major rat and human glutathione S-transferase (GST) isoenzymes by DSF and DDTC was investigated. Reversible inhibition, using 1-chloro-2,4-dinitrobenzene as substrate for the GST alpha-, mu-, and pi-class, expressed as I50 (in microM), ranged from 5-18 (human A1-1), 43-57 (rat 4-4) and 66-83 (rat 1-1), for both DSF and DDTC. The I50 for rat GST theta, using 1,2-epoxy-3-(p-nitrophenoxy)-propane as substrate, was 350 microM for DDTC. The other GSTs were significantly less sensitive to inhibition. The major part of reversible inhibition by DSF was shown to be due to DDTC, formed rapidly upon reduction of DSF by the glutathione (GSH) present in the assay to measure GST activity. The oxidized GSH formed upon reduction of DSF might also have made a minor contribution to reversible inhibition. The rat and human pi-class was, by far, the most sensitive class for time-dependent inactivation by DSF, but no such inactivation was observed for any of the GSTs by DDTC. Moderate susceptibility to inactivation by DSF of all the other GSTs was observed, except for human A2-2, which does not possess a cysteine residue. Consistent with the assumption that a thiol residue is involved in this inactivation, a significant part of the activity could be restored by treatment of the inactivated GST with GSH or dithiotreitol.

Animals↗

Inhibition of lipid peroxidation by disulfiram and diethyldithiocarbamate does not prevent hepatotoxin-induced cell death in isolated rat hepatocytes. A study with allyl alcohol, tert-butyl hydroperoxide, diethyl maleate, bromoisovalerylurea and carbon tetrachloride.

The relationship between lipid peroxidation and cell death, induced by a number of hepatotoxins, was studied in isolated rat hepatocytes. Disulfiram (DSF) and diethyldithiocarbamate (DDC) completely prevented lipid peroxidation, induced by allyl alcohol, tert-butyl hydroperoxide (t-BHP), diethyl maleate (DEM), bromoisovalerylurea (BIU) and carbon tetrachloride (CCl4). Lipid peroxidation was measured by the formation of both thiobarbituric acid positive material and conjugated dienes. However, DSF and DDC did not protect against cell death, induced by these hepatotoxins. In the presence of DSF or DDC, cell death occurred even earlier in time. We conclude that cell death can occur in the absence of lipid peroxidation. Therefore, lipid peroxidation is not a requisite for the induction of cell death.

1-Propanol↗

Lipid peroxidation-dependent and -independent protein thiol modifications in isolated rat hepatocytes: differential effects of vitamin E and disulfiram.

Exposure of isolated rat hepatocytes to allyl alcohol (AA), diethyl maleate (DEM) and bromoisovalerylurea (BIU) induced lipid peroxidation, depletion of free protein thiols to about 50% of the control value and cell death. Vitamin E completely prevented lipid peroxidation, protein thiol depletion and cell death. A low concentration (0.1 mM) of the lipophylic disulfide, disulfiram (DSF), also prevented the induction of lipid peroxidation by the hepatotoxins; however, in the presence of DSF, protein thiol depletion and cell death occurred more rapidly. Incubation of cells with a high concentration (10 mM) of DSF alone led to 100% depletion of protein thiols and cell death, which could not be prevented by vitamin E. The level of free protein thiols in cells, decreased to 50% by exposure to AA, DEM and BIU, could be reversed to 75% of the initial level by dithiothreitol (DTT) treatment, indicating that the protein thiols were partially modified into disulfides and partially into other, stable thiol adducts. The 100% depletion of protein thiols by DSF was completely reversed by DTT treatment. The involvement of lipid peroxidation in protein thiol depletion was studied by measuring the effect of a lipid peroxidation product, 4-hydroxynonenal (4-HNE), on protein thiols in a cell free liver fraction. 4-HNE did not induce lipid peroxidation in this system, but protein thiols were depleted to 30% of the initial value, irrespective of the presence of vitamin E. DTT treatment could reverse this for only 25%. Similar, DSF-induced protein thiol depletion could be reversed completely by DTT. We conclude that (at least) two types of protein thiol modifications can occur after exposure of hepatocytes to toxic compounds: one due to interaction of endogeneously generated lipid peroxidation products with protein thiols, which is not reversible by the action of DTT, and one due to a disulfide interchange between disulfides like DSF and protein thiols, which can be reversed by the action of DTT.

1-Propanol↗

Differential effects of extracellular calcium on lipid peroxidation dependent (ethacrynic acid and allyl alcohol) and lipid peroxidation independent (disulfiram)-induced cytotoxicity in normal and vitamin E-deficient rat hepatocytes.

Hepatocytes have been isolated from normal and vitamin E-deficient rats in which the hepatic vitamin E level was less than 6% that of controls. The hypothesis was tested that extracellular calcium ameliorates chemical-induced cell killing because it decreases the extent of vitamin E loss induced by oxidative stress: such a retarding effect of calcium on cytotoxicity should be lost in hepatocytes from vitamin E-deficient rats. In normal hepatocytes, allyl alcohol and ethacrynic acid induced oxidative stress as indicated by GSH depletion, lipid peroxidation and cell death. Extracellular calcium retarded the induction of lipid peroxidation and cell death without affecting the GSH depletion. In vitamin E-deficient cells, extracellular calcium had lost its protective effect on ethacrynic acid- and allyl-alcohol induced cytotoxicity; it did not affect the GSH depletion and subsequent induction of lipid peroxidation and cell death by ethacrynic acid. However, in vitamin E-deficient hepatocytes, extracellular calcium even potentiated the cytotoxicity of allyl alcohol; under those conditions it also increased GSH loss. Neither in normal, nor in vitamin E-deficient hepatocytes, extracellular calcium had an effect on disulfiram-induced cytotoxicity, i.e. cell death in the absence of lipid peroxidation. These results support the hypothesis that the protecting effect of extracellular calcium on cytotoxicity, associated with lipid peroxidation in normal hepatocytes, is mediated by its protection against intracellular vitamin E loss.

1-Propanol↗

Simultaneous structure-activity determination of disulfiram photolysis products by on-line continuous-flow liquid secondary ion mass spectrometry and enzyme inhibition assay.

Disulfiram (DSF) is used in the treatment of recovering alcoholics and exerts its effect by inhibiting the enzyme aldehyde dehydrogenase (ALDH). We analyzed a mixture of products derived photochemically from DSF with on-line microbore HPLC-continuous-flow liquid secondary ion mass spectrometry (HPLC-CF-LSI-MS). By utilizing the post-HPLC column split of solvent flow, a small proportion (ca. 5%) was sent directly into the mass spectrometer, and the remainder was collected. Simultaneous MS analysis and enzyme inhibition studies on ALDH were then possible. Furthermore, using HPLC-CF-LSI-MS-MS, we were able to structurally characterize an interesting sulfine compound that inhibited ALDH.

Aldehyde Dehydrogenase↗

Distribution of disulfiram in brain after carotid ligation in gerbils.

Aiming whether intraperitoneal administration of disulfiram (tetraethyl thiuram disulfide, DS) achieves potentially therapeutic drug concentrations in brain tissue, the behaviour of blood-brain barrier (BBB) to 14C-labelled DS in cerebral ischemia with and without simultaneous administration of dimethylsulfoxide (DMSO) was studied in Mongolian gerbils subjected to left common carotid artery (CCA) occlusion. The results indicated that: (a) the permeability of DS through the BBB was significantly enhanced in the ischemic brain during the initial 30 min duration after DS administration; (b) administration of DMSO increased the entry of DS into the ischemic brain five-fold during the first 30 min and it was significantly higher even at the 60 min sampling period; (3) in general, the content of DS in the brain was quickly reduced with time.

Animals↗

Interaction between 1,2-dichloroethane and tetraethylthiuram disulfide (disulfiram). II. Hepatotoxic manifestations with possible mechanism of action.

The synergistic hepatotoxicity of dietary disulfiram (DSF) with 1,2-dichloroethane (DCE) subchronically administered by inhalation at three concentration levels (150, 300, and 450 ppm) was studied. The criteria for hepatotoxicity were treatment-related increases in serum activities of sorbitol dehydrogenase, 5'-nucleotidase, and alkaline phosphatase, and in liver-to-body weight ratios. DSF alone did not elicit these responses while DCE at the highest concentration level increased liver-to-body weight ratios and the activity of 5'-nucleotidase. Exposure to DSF alone decreased cytochrome P450 levels, but in combination with DCE, the decrement of cytochrome P450 was additive in a DCE concentration-dependent manner. However, depression of cytochrome P450 by DCE alone was not concentration dependent. Although DSF and DSF/DCE combination increased the activity of glutathione S-transferases (GSTs), both DSF and DCE singly and in combination increased the tissue levels of reduced glutathione (GSH). Evidence is presented showing that the potentiation of the hepatotoxicity of DCE observed in the presence of DSF may be due to an inhibition of microsomal mixed-function oxidase-mediated metabolism of DCE and to a compensatory increase in DCE metabolism to reactive metabolites generated by GST-mediated conjugation of DCE with GSH.

Animals↗

Inhibition of ethanol- and aldehyde-induced release of ethane from isolated perfused rat liver by pargyline and disulfiram.

Acute addition of ethanol or acetaldehyde to the isolated, perfused rat liver leads to an increase in ethane and n-pentane release. These volatile hydrocarbons are known to originate from the peroxidation of polyunsaturated fatty acids. The effects are half-maximal at 0.5 mM ethanol or 20 microM acetaldehyde in the entering perfusate. Propionaldehyde and benzaldehyde are also able to elicit ethane release. Pargyline and disulfiram, inhibitors of aldehyde oxidation, inhibited the extra ethane release in all cases. The inhibitory effect of pargyline is suppressed during addition of metyrapone. The study indicates that the oxidation of acetaldehyde and not of ethanol itself is the step responsible for increased ethane formation by the perfused rat liver during ethanol infusion.

Acetaldehyde↗

Influence of disulfiram on mutagenicity of the urinary metabolites of 2-acetylaminofluorene and N-hydroxy-2-acetylaminofluorene in the Salmonella test system.

Male Sprague-Dawley rats were fed control diet or 0.65% disulfiram (DS) in the diet for up to 20 days. Groups of these animals were injected with 2-acetylaminofluorene (AAF) or N-hydroxy-2-acetylaminofluorene (N-OH-AAF) after 3, 10 and 20 days, in order to study the effects of DS administration on the mutagenic activity of urinary metabolites of the carcinogens. Administration of DS alone for 20 days did not increase significantly the mutagenicity of urine. Urine from rats administered either of the carcinogens showed mutagenic activity which was increased appreciably in the presence of S9 and beta-glucuronidase. Urine from rats which also were fed DS showed an even greater increase in revertants under these conditions. The results indicate that DS increased the excretion of glucuronide metabolites of the carcinogens.

2-Acetylaminofluorene↗

Effect of disulfiram administration on brain tryptophan, serotonin and peripheral tryptophan content.

The prophylactic deterrent effect of disulfiram (DS) has been attributed to its ability to exacerbate sympathetic function. Though there are reports to indicate that DS administration could as well affect the neurotransmitter metabolism, few reports implicate the possibility of central nervous system (CNS) mediated anticraving effect of the drug. The present study involving the oral administration of DS to rats for 45 days has clearly shown a significant increase in 5-HT (815.4 +/- 74.7 ng/g, P < 0.01) and 5-HIAA (506.1 +/- 86.3 ng/g, P < 0.02) contents in brain when compared to control rats. The observed increase in 5-HT and 5-HIAA content was found to correlate (zeta = 0.89) with the concomitant increase in brain tryptophan content (4.15 +/- 1.05 nmol/g, P < 0.001) following DS administration. Further, the study on peripheral tryptophan content has shown an increase in both total and free fraction (ultrafiltrate) of plasma, which in turn was found to have an inverse relationship (zeta = -0.94, P < 0.05) with the decrease in liver tryptophan content following DS administration. Thus the observed increase in brain 5-HT level is attributed to the ability of DS to mobilise peripheral tryptophan for 5-HT synthesis in CNS. As there are reports to imply the hyposerotonergic function as responsible for craving, the present findings, that DS could enhance the 5-HT metabolism in brain, may partially explain the CNS mediated anticraving effect of DS.

Animals↗