Studies in potential filaricides. 18. Synthesis of 2,2'-disubstituted 5,5'-dibenzimidazolyl ketones and related compounds as potential anthelmintics

A series of 2,2'-disubstituted 5,5'-dibenzimidazolyl ketones and related compounds have been synthesized of which 2,2'-bis(carbomethoxyamino)-5,5'-dibenzimidazolyl ketone exhibited a broad spectrum of anthelmintic activity in experimental animals. At doses of 10-50 mg/kg given intraperitoneally, 5 killed 100% of the adult worms of Litomosoides carinii, Dipetalonema viteae, and Brugia malayi. By the oral route the macrofilaricidal efficacy of 5 was 97-100% at 100-200 mg/kg X 5 days. The treated animals showed gradual disappearance of microfilariae and before autopsy they became amicrofilariaemic. Some of the compounds also showed 100% efficacy against the human hookworms and tapeworm, Ancylostoma ceylanicum in hamsters, and Hymenolepis nana in rats at a single oral dose of 50-250 mg/kg. Compound 5 was also effective against Syphacia obvelata in mice at a single oral dose of 100 mg/kg and was found to be well tolerated by mice up to an oral dose of 2500 mg/kg.     

Antipicornavirus activity of some diaryl methanes and aralkylaminopyridines

Sixteen diarylmethanes and ten aralkylaminopyridines were initially evaluated for their in vitro activity against rhinoviruses 1A, 2 and 64 and against coxsackievirus A21 and for their oral prophylactic and therapeutic activity in mice challenged with coxsackievirus A21. Based on these preliminary studies the diarylmethane (3,4-dichlorophenoxy)-(5 methylsulfonyl-2-pyridinyl)-methane and the aralkylaminopyridine (2-(3,4-dichlorobenzylamino)-5-methylsulfonylpyridine were compared with their oxygen bridged analogue 2-(3,4-dichlorophenoxy)-5-(methylsulfonyl)pyridine for in vitro activity against a larger number of picornaviruses and for their in vivo protective efficacy in dose response assays. All three compounds exhibit similar in vitro activity inhibiting 12 to 15 (52.2-65.3%) of the 23 picornaviruses tested at concentrations of less than 5.0 micrograms/ml. However, the aralkylaminopyridine was found to be the most active in vivo; significantly protecting coxsackievirus A21 challenged mice after a single oral dose of 37.5 mg/kg (P less than or equal to 0.05) and during a continuous oral dose regimen of as low as 18.8 mg/kg per day (P less than 0.01).     

疟原虫组织期裂殖体杀灭剂的研究:2-取代苄氧基(或甲氧基)-5-取代苯氧基-伯氨喹类似物的合成

本文报道了间日疟根治药伯氮喹2位引入取代苄氧基或甲氧基,5位引入取代苯氧基的类似物的合成。其中以化合物39及45对疟原虫组织期裂殖体的作用最强,约氏疟原虫子孢子感染的小鼠喂服100mg/kg单剂,分别有80%及90%的受试小鼠未查见原虫血症。化合物45降至20mg/kg单剂时,80%的受试小鼠也未出现原虫;对小鼠的急性毒性低于伯氨喹。     

2-Phenyl-3-(quinolizidin-1-yl)-5-substituted indoles as platelet antiaggregating agents

A set of ten 2-phenyl-3-(quinolizidin-1-yl)-5-substituted indoles was prepared through the Fischer cyclization of lupinyl- and epi-lupinylphenylketone 4-substituted phenylhydrazones.Compounds were tested for antiaggregating activity on human platelets activated by adenosine diphosphate (ADP), collagen and adrenaline. At 2.5 x 10(-4) M concentration most compounds strongly inhibited the aggregation induced by all the agonists considered and many of them still displayed good activity at 0.625 x 10(-4) M concentration. The least active (1c) and one of the most active (1d) compounds were also tested for antiaggregating activity on rabbit platelets activated by ADP, PAF and sodium arachidonate. Both the compounds were active against ADP and PAF, but only 1d inhibited the arachidonate-induced aggregation (100% at 8 x 10(-6) M concentration) and increased the bleeding time in mice. The same compounds were subjected to a general pharmacological screening and found to display several activities; of particular interest was the dose dependent reduction of serum cholesterol and heparin precipitating betalipoproteins in hypercholesterolemic mice exerted by 1c, which was still significant at the oral dose of 10 mg/kg.     

Newer indolyl imidazolones as anti-inflammatory agents

Sixteen new 1,2-disubstituted-4-(indol-3'-yl)methylene imidazol-5-ones were synthesized by the condensation of oxazolone with different aryl amines and evaluated as to their anti-inflammatory and antiproteolytic activities. These derivatives showed 2-38% protection against carrageenin-induced paw oedema in albino rats at a dose of 100 mg/kg p.o. All compounds showed antiproteolytic activity. The degree of inhibition against trypsin-induced hydrolysis of casein ranged from 10 to 75% at a concentration of 4 X 10(-4) mol/l. Furthermore, active compounds of the series were also screened for their analgesic activity against aconitine-induced writhing in albino mice. The toxicity of the compounds was reflected by their approximate LD50 values.     

Clinical evaluation of cefixime in children

A new beta-lactamase-stable oral cephem antibiotic, cefixime (CFIX), was evaluated for safety, efficacy and pharmacokinetics in children. CFIX was effective in 19 of 20 cases (95%) with bacterial infections. The drug was especially effective against the cases of pneumonia due to beta-lactamase-producing H. influenzae or B. catarrhalis. Pharmacokinetic parameters of CFIX (3 mg/kg) with premeal administration were as follows: Kel 0.328 +/- 0.066 hr-1, T 1/2 2.14 +/- 0.36 hrs, AUC 10.9 +/- 8.7 micrograms X hr/ml, and Vd/F 1.64 +/- 1.42 L/kg. In most of the cases tested, the urinary excretion rate in 12 hours was 5 to 17%. A dose of 3 mg/kg twice daily seems to be adequate for a regular treatment.     

RU 29 246, the active compound of the cephalosporin prodrug-ester HR 916. III. Pharmacokinetic properties and antibacterial activity in vivo.

The pharmacokinetics of the broad spectrum cephem RU 29 246 and its prodrug-ester HR 916 B were investigated in mice, rats and dogs and compared to those of cefpodoxime proxetil, cefuroxime axetil and cefixime. HR 916 B is well absorbed following oral administration and efficiently converted to the antibacterially active form. In mice, mean peak blood levels of 31.1 micrograms/ml of the parent compound were recorded within 20 minutes after oral administration of a single dose equivalent to 40 mg/kg RU 29 246. The bioavailability calculated on the basis of the areas under the concentration-time curves (AUC) and the urinary recoveries was about 90%. In rats, peak blood levels of 14.5 micrograms/ml were obtained 1 hour after an oral 20 mg/kg dose. The bioavailability was calculated as 70%. In dogs, 40% of an oral 10 mg/kg dose was recovered in the urine within 24 hours. Cmax was 15.9 micrograms/ml at 4.6 hours. Mean elimination half-lives of RU 29 246 were 0.35, 0.5 and 2.1 hours in mice, rats and dogs, respectively. After an oral HR 916 B dose equivalent to 50 mg/kg of RU 29 246, tissue concentrations at 0.5 hour ranged between 0.8 micrograms/g in brain and 95.7 micrograms/g in murine kidneys. These values of HR 916 B are similar to, or distinctly higher than, those of the reference compounds. Of the oral cephalosporins tested, HR 916 B had the most balanced antibacterial spectrum. With ED50s of between 0.9 and 11.5 mg/kg against staphylococci, its activity was similar to that of the additional reference compound cefaclor and higher than that of cefuroxime. Cefixime and cefpodoxime proxetil displayed low antistaphylococcal activity or were inactive. In septicemias with Enterobacteriaceae, cefixime and cefpodoxime proxetil were more potent than HR 916 B and cefaclor. Cefuroxime axetil was inactive against most of these infections. HR 916 B was also highly effective against murine lung infections caused by Klebsiella pneumoniae DT-S or Streptococcus pneumoniae 1147.     

Cytogenetic and embryotoxic effects of bromophos and demethylbromophos

The organophosphorus pesticide bromophos and the tetramethylammonium and sodium salts of demethylbromophos were tested for cytogenetic and embryotoxic activity on mice of different strains. Single intraperitoneal (ip) doses of 183.0 mg/kg (0.5 mmol/kg) and 73.2 mg/kg (0.2 mmol/kg) bromophos caused a significant enhancement in the percentage of chromosome aberrations in bone marrow cells of CFLP mice; similar effects were produced by a single dose of 0.2 mmol/kg demethylbromophos tetramethylammonium salt and demethylbromophos sodium salt trihydrate, respectively, indicating that the cytogenetic activity of bromophos is not connected with its alkylating properties. After repeated ip or oral administration to pregnant mice of strains AB Jena/Halle and DBA, none of the tested compounds showed a marked influence on the total implantation losses, although in some cases the postimplantation losses were significantly increased.     

Gastroprotective and cytotoxic effect of dehydroabietic acid derivatives.

Dehydroabietic acid derivatives have been reported to display antisecretory and antipepsin effect in animal models. Some 19 dehydroabietic acid diterpenes were prepared and assessed for gastroprotective activity in the HCl/EtOH-induced gastric lesions in mice as well as for cytotoxicity in human lung fibroblasts (MRC-5) and human epithelial gastric (AGS) cells. At a single oral dose of 100 mg kg(-1), highest gastroprotective effect was provided by dehydroabietanol, its corresponding aldehyde, dehydroabietic acid (DHA) and its methyl ester, N-(m-nitrophenyl)-, N-(o-chlorophenyl)- and N-(p-iodophenyl)abieta-8,11,13-trien-18-amide (compounds 12-14), N-2-aminothiazolyl- and N-benzylabieta-8,11,13-trien-18-amide (compounds 18-19) being as active as lansoprazole at 20 mg kg(-1) and reducing the lesion index by at least 75%. In the compound series including the alcohol, ester, aldehyde, acid and methyl ester at C-18 (compounds 1-9), highest activity was related with the presence of an alcohol, aldehyde, acid or methyl ester at C-18, the activity being strongly reduced after esterification. The cytotoxicity of the compounds 1-9 towards AGS cells and fibroblasts was higher than the values for the amides 10-19. In the compounds 10-19, the best gastroprotective effect was observed for the aromatic amides 12-14 (75-85% inhibition of gastric lesions) bearing a nitro or halogen function in the N-benzoyl moiety. Lowest cytotoxicity was found for the amides, with IC(50) values >1000 microM for fibroblasts and from 200 up to >1000 microM for AGS cells, respectively. The N-2-aminothiazolyl- and N-benzylamide derivatives were also very active as gastroprotectors with higher cytotoxicity against AGS cells.     

Influence of Fungicidal Activity against Candida tropicalis on the Efficacy of Micafungin and Liposomal Amphotericin B in a Neutropenic Murine Lethal Infection Model

Objectives: To investigate the correlation between in vitro killing activity and in vivo efficacy of micafungin (MCFG) and liposomal amphotericin B (L-AMB) against Candida tropicalis in a neutropenic murine lethal infection model. Methods: Candida albicans (one strain) and C. tropicalis (three strains) were tested in time-kill studies. Cyclophosphamide-treated mice were inoculated intravenously with each strain. One day after inoculation, antifungals were administered intravenously once daily for 1 or 3 days. Results: MCFG exhibited fungicidal activity against C. albicans ATCC 90029 and C. tropicalis SP-20142, and fungistatic activity against C. tropicalis ATCC 42678 and SP-20047. The ED(50)s (dosage that results in 50% survival) of MCFG for C. tropicalis ATCC 42678 and SP-20047 (4.1-50 mg/kg) were higher than those for other strains (1.6-12 mg/kg). A 1-day course of MCFG was not effective against C. tropicalis ATCC 42678 and SP-20047 at the clinical dose (5 mg/kg), which achieved an AUC level almost equal to that of 100 mg in humans, whereas a 3-day course of 5 mg/kg MCFG was efficacious against all strains. In contrast, L-AMB showed fungicidal activity against all strains tested and the ED(50)s of L-AMB were 0.08-0.65 mg/kg. In both treatment regimens, the minimum effective doses of L-AMB (≤0.5 mg/kg) were less than the clinical dosage (≤5 mg/kg). Conclusions: The in vivo efficacy of MCFG and L-AMB showed a correlation with the in vitro killing activity. At the clinical dose, L-AMB exerted anti-C. tropicalis activity within a shorter treatment period than MCFG.     

Synthesis of some 3-(arylalkylthio)-4-alkyl/aryl-5-(4-aminophenyl)-4H-1,2,4-triazole derivatives and their anticonvulsant activity

A series of novel 3-[[(substituted phenyl)methyl]thio]-4-alkyl/aryl-5-(4-aminophenyl)-4H-1,2,4-triazoles 11-20 and several related Schiff's bases, 3-[[(substituted phenyl)-methyl]thio]-4-alkyl/aryl-5-[[[(substituted phenyl/5-nitro-2-furyl)methylene]amino]-phenyl]-4H-1,2,4-triazoles 21-31 were synthesized for evaluation of their biological properties. Structures of the synthesized compounds were confirmed by the use of their spectral data besides elemental analysis. All compounds were evaluated for their anticonvulsant activity by maximal electroshock (MES), subcutaneous pentylenetetrazole (scPTZ) and neurotoxicity (NT) screens. A number of triazole derivatives, exhibited protection after intraperitoneal administration at the dose of 100 and 300 mg/kg in one or both models employed. Compounds 12, 13 and 14 were subjected to oral MES screening in rats at 30 mg/kg and were observed to protect 50% of the animals employed in the experiment. Antimicrobial and antituberculosis activity of these compounds 11-31 were also screened. Some of the tested compounds showed marginal activity against M. tuberculosis H37 Rv.     

Substituted thiazolidones: selective inhibition of nicotinamide adenine dinucleotide-dependent oxidations and evaluation of their CNS activity.

Eight 2-arylimino-3-(3-N-morpholinopropyl) thiazolid-4-ones were synthesized from the corresponding 1-aryl-3-(3-N-morpholinopropyl) thiocarbamides, characterized, and tested for their effects on the cellular respiratory activity of rat brain homogenates. All substituted 4-thiazolidones selectively inhibited nicotinamide adenine dinucleotide (NAD)-dependent oxidations of pyruvate, citrate, DL-isocitrate, alpha-ketoglutarate, malate, beta-hydroxybutyrate, L-glutamate, and NADH, while the NAD-independent oxidation of succinate remained unaltered. All thiazolidones possessed some degree of anticonvulsant activity against pentylenetetrazol-induced convulsions, and the protection afforded by these compounds at a dose of 100 mg/kg ranged from 30 to 80%. The low toxicity possessed by most of these thiazolidones was reflected by their approximate LD-50 values from 300 mg/kg to greater than 1000 mg/kg. In the present study, the anticonvulsant activity possessed by these substituted 4-thiazolidones was unrelated to their ability to inhibit selectively the NAD-dependent oxidations by rat brain homogenates. These thiazolidones exhibited depression of the CNS activity which, in some cases, was associated with the increase in respiration. All thiazolidones potentiated pentobarbital (sodium) sleeping time in mice when administered in a dose of 100 mg/kg.     

Protective effects of immunoactive peptide, FK565 against systemic and local infections with herpes simplex virus and murine cytomegalovirus and respiratory tract infection with influenza virus in mice.

The protective effects of FK565 against systemic infections with herpes simplex virus (HSV) and murine cytomegalovirus (MCMV), respiratory tract infection with influenza virus and zosteriform rash with HSV investigated in mice. FK565 showed excellent protective activities against systemic infections with both acyclovir (ACV)-sensitive and -resistant HSV at intravenous and subcutaneous doses of 0.1 and 1 mg/kg and oral dose of 1 mg/kg. FK565 showed superior protective activities at subcutaneous doses of 0.01 and 0.1 mg/kg compared to ACV at subcutaneous dose of 15 mg/kg against MCMV infection. In respiratory tract infection with influenza virus, FK565 showed potent protective effects at intravenous, subcutaneous and oral doses of 0.001 to 1 mg/kg. FK565 markedly inhibited zosteriform spread of HSV on the flank skin at an intravenous dose of 0.1 mg/kg and the mice given FK565 survived longer than the control mice. The peritoneal exudate cells from FK565-treated mice suppressed the growth of HSV in mouse embryo fibroblast more strongly than those from the control mice, although FK565 had no direct antiviral activity against HSV. These findings suggest that FK565 enhanced the host defense ability against viral infections by nonspecific activation of macrophages.     

Aegle marmelos (L.) Correa inhibits the proliferation of transplanted Ehrlich ascites carcinoma in mice

The anticancer effect of hydroalcoholic extract of Aegle marmelos (AME) was studied in the Ehrlich ascites carcinoma bearing Swiss albino mice. The spatial effect of various AME administration schedules showed that six-day administration increased the survival of tumor bearing mice. The best antineoplastic action of AME was obtained when AME administered through intraperitoneal route than the oral route at equimolar dose. Administration of AME once daily for six consecutive days to the tumor bearing mice caused a dose dependent remission of the tumor at 400 mg/kg body weight, where the greatest antitumor effect was observed and the higher doses showed toxic manifestations. A 24-d lengthening in life span was observed in EAC animals treated with 400 mg/kg AME. This dose of 400 mg/kg was considered as the best dose, where the animals survived up to 43 d post-tumor-cell inoculation as against no survivors in the saline treated control group. The antitumor activity when tested for different schedules for triple administrations, the best effect was observed for 1-2-3, followed by 1-3-5 and 1-5-9 days, respectively. Stage specific evaluation of AME inhibited the increase in body weight gain in animals due to tumor development during early stages only. The AME treatment resulted in a dose dependent elevation in the median survival time (MST) and average survival time (AST) up to 400 mg/kg AME and decline thereafter. The effective dose of 400 mg of AME is 1/6th of the LD50 dose, which increased the MST and AST up to 29 and 27 d, respectively. The acute toxicity study of AME showed that the drug was non-toxic up to a dose of 1750 mg/kg b. wt. The LD10 and LD50 was found to be 2000 and 2250 mg/kg.     

Gastroprotective effect and cytotoxicity of labdenamides

Some 18 aromatic amides from the labdane diterpenes 15-acetoxyimbricatolic acid and 15-acetoxylabd-8(9)-en-19-oic acid were prepared and assessed for their gastroprotective effect in the HCl/EtOH-induced gastric lesion model in mice. The analysis of the gastroprotective activity of the benzylamides belonging to the series 8(9)- and 8(17)-ene was undertaken at doses of 12.5, 25 and 50 mg/kg in the HCl/EtOH-induced gastric lesion model in mice. A statistically significant gastroprotective effect was observed for 15-acetoxylabd-8(9)-en-19-oic acid benzylamide starting at 12.5 mg/kg, reducing the gastric lesions by 50%, while 15-acetoxylabd-8(17)-en-19-oic acid benzylamide reduced lesions by 66% at 25 mg/kg. The 25 mg/kg dose was used for the comparison of the different amides. At 25 mg/kg, the highest gastroprotective effect was observed for the benzyl- and 3-bromophenylamides from 15-acetoxyimbricatolic acid as well as for the benzyl- and P-toluidylamides of 15-acetoxylabd-8(9)-en-19-oic acid, being as active as lansoprazole at 20 mg/kg. Most compounds displayed low toxicity against epithelial gastric (AGS) and human lung fibroblasts cells, with IC50 values>1000 microM. The highest cytotoxicity towards AGS cells was observed for the 2-bromophenyl- and 2-hydroxy-5-chlorophenylamides in both diterpene series, with IC50 values in the range of 14-34 microM towards AGS cells and 10-37 microM towards fibroblasts, respectively.     

3,5-Diaryl-2-aminopyridines as a novel class of orally active antimalarials demonstrating single dose cure in mice and clinical candidate potential

A novel class of orally active antimalarial 3,5-diaryl-2-aminopyridines has been identified from phenotypic whole cell high-throughput screening of a commercially available SoftFocus kinase library. The compounds were evaluated in vitro for their antiplasmodial activity against K1 (chloroquine and drug-resistant strain) and NF54 (chloroquine-susceptible strain) as well as for their cytotoxicity. Synthesis and structure-activity studies identified a number of promising compounds with selective antiplasmodial activity. One of these frontrunner compounds, 15, was equipotent across the two strains (K1 = 25.0 nM, NF54 = 28.0 nM) and superior to chloroquine in the K1 strain (chloroquine IC(50) K1 = 194.0 nM). Compound 15 completely cured Plasmodium berghei-infected mice with a single oral dose of 30 mg/kg. Dose-response studies generated ED(50) and ED(90) values of 0.83 and 1.74 mg/kg for 15 in the standard four-dose Peters test. Pharmacokinetic studies in the rat indicated that this compound has good oral bioavailability (51% at 20 mg/kg) and a reasonable half-life (t(1/2) ～ 7-8 h).     

Synthesis and anticonvulsant and sedative-hypnotic activity of 4-(alkylimino)-2,3-dihydro-4H-1-benzopyrans and -benzothiopyrans

A series of 4-(alkylimino)-5-hydroxy-7-alkyl-2,3-dihydro-4H-1-benzopyrans and -thiopyrans were synthesized and evaluated for anticonvulsant activity. Preliminary screening of these compounds revealed that 2,2-dimethyl-4-[(2-hydroxyalkyl)imino]-5-hydroxy-7-pentyl-2,3- dihydro-4H-1-benzopyrans 19 and 29, the 7-butyl analogue 34, and the corresponding 7-pentyl-4H-1-benzothiopyrans 38 and 39 had the most promising anticonvulsant activity. Synthesis of both enantiomers of 29 and 39 indicated that the R isomers 30 and 40 were the most active and showed very good protection against MES, pentylenetetrazole, and mercaptopropionic acid induced seizures after oral administration in mice. In the Irwin test these compounds showed a generalized depressant activity but at dosages higher than those showing anticonvulsant activity, whereas acute toxicity after oral administration was low (LD50 higher than 400 mg/kg).     

Novel quinazoline and acetamide derivatives as safe anti-ulcerogenic agent and anti-ulcerative colitis activity

Two novel quinazoline derivatives named as; 3-[(4-hydroxy-3-methoxy-benzylidene)-amino]-2-p-tolyl-3H-quinazolin-4-one (5) and 2-p-Tolyl-3-[3,4,5-trimethoxy-benzylidene-amino]-3H-quinazolin-4-one (6) in addition to one acetamide derivative named as 2-(2-Hydroxycarbonylphenylamino)-N-(4-aminosulphonylphenyl) 11 were synthesized, and evaluated for their anti-ulcerogenic & Anti-Ulcerative colitis activities.All of the three compounds showed curative activity against acetic acid induced ulcer model at a dose of 50 mg/kg, they produced 65%, 85% & 57.74% curative ratio for compounds 5, 6 & 11 respectively. The effect of the tested compounds 5, 6 & 11 at dose 50?mg/kg were significantly (P < 0.01) more effective than dexamesathone (0.1?mg/kg) in reducing all parameters.Compounds showed curative activity of for peptic ulcer (induced by absolute alcohol (at a dose of 50?mg/kg, it produced Curative of control ulcer 56.00%, 61.70% & 87.1% for compounds 5, 6 & 11 respectively at dose 50?mg/kg, while the standard drug (Omeprazole 20?mg/kg) produced 33.3%. In both tests, the activity of our target compounds were higher than the standard drugs used for treatment of peptic ulcer and ulcerative colitis. No side effects were reported on liver and kidney functions upon prolonged oral administration of this compounds.     

Synthesis and studies on antidepressant and anticonvulsant activities of some 3-(2-thienyl)pyrazoline derivatives

In this study, the synthesis of twelve 3-(2-thienyl)pyrazoline derivatives are described. The structures of all compounds were confirmed by UV, IR, (1)H-NMR, mass spectral data, and microanalyses. In the pharmacological studies, antidepressant and anticonvulsant activities of these compounds have been screened. The antidepressant activities of the compounds were investigated by Porsolt's behavioral despair test (forced swimming) on albino mice and compared with tranylcypromine. Among the compounds examined, the compounds 9 and 12 showed significant antidepressant activity. Anticonvulsant activities of the compounds were determined by maximal electroshock seizure (MES) and subcutaneous pentylenetetrazole (metrazol) (scMet.) tests, neurotoxicities were determined by rotarod toxicity test on albino mice. Compound 8 was found to be protective against MES in the range of 30-300 mg/kg dose levels at four hours. None of the synthesized compounds showed neurotoxicity at 30-300 mg/kg dose levels.     

Attenuation by methyl mercury and mercuric sulfide of pentobarbital induced hypnotic tolerance in mice through inhibition of ATPase activities and nitric oxide production in cerebral cortex

This study is aimed at exploring the possible mechanism of hypnosis-enhancing effect of HgS or cinnabar (a traditional Chinese medicine containing more than 95% HgS) in mice treated with pentobarbital. We also examined whether the effect of HgS is different from that of the well-known methyl mercury (MeHg). After a short period (7 days) of oral administration to mice, a nontoxic dose (0.1 g/kg) of HgS not only significantly enhanced pentobarbital-induced hypnosis but also attenuated tolerance induction; while a higher dose (1 g/kg) of HgS or cinnabar exerted an almost irreversible enhancing effect on pentobarbital-hypnosis similar to that of MeHg (2 mg/kg) tested, which was still effective even after 10 or 35 days cessation of administration. To study comparatively the effects of different mercury forms from oral administration of MeHg and HgS on membrane ATPase activities of experimental mice, analysis of the Hg content in the cerebral cortex revealed that correlated with the decrease of Na(+)/K(+)-ATPase and Ca(2+)-ATPase activities. Furthermore, NO levels of blood but not that of cerebral cortex were also decreased by mercuric compounds. Although pentobarbital alone enhanced cytochrome p450-2C9 in time dependent manner, all of mercurial compounds tested had no such effect. All of these findings indicated that the mercurial compounds including cinnabar, HgS and MeHg exert a long-lasting enhancing hypnotic activity without affecting pentobarbital metabolism, which provides evidence-based sedative effect of cinnabar used in Chinese traditional medicine for more than 2,000 years. The nontoxic HgS dosing (0.1 g/kg/day) for consecutive 7 days is perhaps useful for delaying or preventing pentobarbital-tolerance.