Suppression of cholinergic activity via the dopamine D2 receptor in the rat striatum

The effect of dopamine (DA) D2 receptor on extracellular choline (Ch) and acetylcholine (ACh) levels in rat caudate-putamen (striatum) was investigated by means of microdialysis. The systemic, intraperitoneal (i.p.), injection of (+/-)-2-(N-phenylethyl-N-propyl) amino-5-hydroxytetralin (N-434), a specific DA D2 receptor agonist decreased striatal ACh release in a dose-dependent manner and the i.p. injection of sulpiride, a specific DA D2 receptor antagonist, increased the ACh release in a dose-dependent manner. In contrast, extracellular Ch levels were increased by the agonist and decreased by the antagonist. An increased Ch uptake was observed in sulpiride-treated rats and a decreased Ch uptake was observed in N-434-treated rats. The effects of the D2 agonist on extracellular Ch, ACh and Ch uptake were completely antagonized by the D2 antagonist. These results suggest clearly an inhibition of ACh release by D2 receptor activation, contrasting with previous findings on DA-ACh interaction. The inverse relationship between extracellular Ch and ACh reflects a change in the Ch uptake owing to a change in cholinergic neuron activity via the D2 receptor mechanisms.

Regulation of dopamine D1 and D2 receptors on striatal acetylcholine release in rats

The effects of dopamine (DA) D1 and D2 receptors on striatal acetylcholine (ACh) releases were investigated by in vivo microdialysis. All drugs were applied via dialysis membrane directly to the striatum. The levels of ACh release were increased by 10(-4) M SKF38393, a D1 receptor agonist. Although 10(-4) M SCH23390, a D1 receptor antagonist, exhibited an increase in the levels of ACh release, the agonist (10(-4) M) induced-increase in the levels of ACh release was suppressed by coperfusion of the antagonist (10(-4) M). In contrast, the levels of ACh release were decreased by the D2 receptor agonist, N-434, in a dose-dependent manner (10(-4) M to 10(-7) M) and increased by the D2 receptor antagonist, sulpiride, in a dose-dependent manner (10(-5) M to 10(-7) M). The agonist (10(-5) M) induced-decrease in the levels of ACh release was suppressed by coperfusion of the antagonist (10(-4) M). Coperfusion of D1 (10(-4) M) and D2 (10(-5) M) agonists blocked both effects of respective drug alone. In order to clarify the effect of endogenous DA, two drugs with different mechanisms for enhancing DA concentration in the synaptic cleft, the DA release-inducer methamphetamine, and the DA uptake inhibitor nomifensine were perfused separately. Both (10(-4) M to 10(-5) M) produced a dose- and a time-dependent decrease in the levels of ACh release. Significant higher levels of ACh release were observed in the striatum of the 6-hydroxydopamine (8 micrograms/10 microliters)-treated rats with significant depletion of striatal DA content. These results suggest that in striatal DA-ACh interaction ACh release, as cholinergic interneuron's activity, is tonically inhibited via the D2 receptor, mainly by dopaminergic input, and the D1 receptor probably modifies the effect of the D2 receptor indirectly.

Uric acid changes in serum during different forms of hepatic vascular inflow occlusion

The present study was conducted to develop an efficient marker which can evaluate the influence of the occlusion of hepatic vascular inflow, which technique is commonly used in major liver surgery or in liver transplantation. Serum samples from the rats induced by hepatic vascular inflow occlusion were analyzed with high performance liquid chromatography with the electrochemical detection, and a substance which changed in accordance with the duration of the occlusion was obtained. Both the retention time and the ultraviolet absorption spectra of the substance completely agreed with those of an authentic uric acid and the substance was ultimately determined to be uric acid. To evaluate the changes in serum uric acid during different forms of hepatic vascular inflow occlusion we devised the four types of experimental model, viz. the occlusion of hepatic artery, portal vein, both hepatic artery and portal vein and both hepatic artery and portal vein of left hepatic lobes. From the device of experiments our results indicated that in the early stage of hepatic vascular inflow occlusion the high values of serum uric acid did not reflect the damage of hepatic circulation but rather responded to the intestinal congestion. Our results also indicated that even after the declamping of hepatic vascular inflow if high values of serum uric acid are prolonged it means the deterioration of the portocaval circulation including both intestinal and hepatic circulation. So that the evaluation of the severity of injured liver due to hepatic vascular inflow occlusion should be done with the caution especially in vivo study when uric acid values are used as a marker.

Hypothalamic cholinergic activity and 2-deoxyglucose-induced hyperglycemia

To clarify the role of the hypothalamic cholinergic system in the regulation of peripheral glucose metabolism, we investigated hypothalamic cholinergic activities after administration of 2-deoxyglucose (2-DG). Intravenous administration of 2-DG (500 mg/kg) caused neuroglycopenia and marked hyperglycemia; the level of plasma glucose increased to 210% of the initial levels of 20 min. For evaluation of the cholinergic activity, we employed a microwave device and subsequently analyzed the contents of acetylcholine (ACh) and choline after microdissection of the hypothalamic nuclei, ventromedial hypothalamic nucleus (VMH), lateral hypothalamus (LH), and paraventricular nucleus (PVN). In addition, we analyzed fluctuation of extracellular levels of ACh using in vivo brain microdialysis. A decrease in the ACh content, and a corresponding increase in the choline content, was observed in those hypothalamic nuclei min after administration of 2-DG. In the microdialysis perfusate, on the other hand, extracellular level of ACh was increased by 2-DG administration. These data show that ACh release, which is cholinergic activity, was increased after 2-DG administration. Our results suggest the involvement and importance of the hypothalamic cholinergic system in 2-DG-induced hyperglycemia.

Effects of MK-801 and pentobarbital on cholinergic terminal damage and delayed neuronal death in the ischemic gerbil hippocampus

The present study covers both the effects of MK-801, a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist, and pentobarbital on cholinergic terminal damage and delayed neuronal death (DND) in ischemic gerbil. To study the above effects, in vivo microdialysis, immunohistochemical, and morphological techniques were used. MK-801 (3 mg/kg) or pentobarbital (50 mg/kg) were injected intraperitoneally 1 h or 30 min before 5 min ischemia, respectively. Each estimation was then carried out 4, 7, or 14 days after ischemia. Ischemia induced a significant decrease in acetylcholine (ACh) release and a disappearance of choline acetyltransferase (ChAT)-immunoreactivity in the hippocampus in addition to inducing DND. On day 4, MK-801 protected ischemia-induced DND in the hippocampal CA1 subfield. However, MK-801 had no effect against the decrease in ACh release in spite of protection of the decrease in ChAT-immunoreactivity. On day 7 and 14, no protective effect of MK-801 was observed in all estimations. It became clear that the mechanism of cholinergic terminal dysfunction is different from that involved in pyramidal cell death, i.e., excitative neurotoxicity induced by overabundant extracellular glutamate. Pentobarbital also provided protection against DND. However, protective effects of pentobarbital on the decrease in ACh release and the low ChAT-immunoreactivity were incomplete. Our present study indicated a limitation on the efficacy of NMDA receptor antagonist and barbiturate against cerebral ischemia.

Effects of hepatic nerve stimulation on blood glucose and glycogenolysis in rat liver: studies with in vivo microdialysis

In vivo microdialysis was applied to investigate the effects of hepatic nerve stimulation on glycogenolysis in rat liver under anesthesia. We analyzed the norepinephrine (NE) outflow and glucose output from the liver through the measurement of NE and glucose in the microdialysis dialyzate, as well as the plasma glucose level. Stimulation of the hepatic nerves (10 Hz, 20 V, 2 ms, 20 s every minute) increased NE outflow and glucose output from the liver. The blood glucose level increased by 1.5-1.6 times over the basal level at the end of the 10 min intermittent stimulation. Bilateral adrenalectomy and pancreatectomy did not abolish the glycogenolysis that was induced by the nerve stimulation. Phentolamine an alpha-antagonist, reduced the effects of nerve stimulation on the glucose output and the plasma glucose level. Phentolamine caused an increase in the NE outflow. Quinacline, an inhibitor of phospholipase A2, inhibited the glycogenolytic nerve effects without any inhibition of the NE outflow. These data show that hepatic nerve stimulation produces glycogenolysis via alpha-adrenergic mechanism and partly mediated by eicosanoids, and that microdialysis is a useful and simple method for the study of liver metabolism in physiological conditions.

Evaluation of skin sensitization potential of nickel, chromium, titanium and zirconium salts using guinea-pigs and mice

Contact sensitization capacity of four metal salts, nickel sulphate (NiSO4), potassium dichromate (K2Cr2O7), titanium chloride (TiCl4) and zirconium chloride (ZrCl4), was evaluated using guinea-pigs and mice. In the guinea-pig sensitization tests, we set up an injection concentration to 1% for all chemicals, and changed the challenge concentration. Guinea-pigs were sensitized with NiSO4, K2Cr2O7 and TiCl4. Among the test metal salts, K2Cr2O7 showed the highest sensitization rate and strongest skin reactions. ZrCl4 did not cause any sensitization responses under our experimental conditions. Minimum challenge concentration to cause a skin response was < 0.25% for K2Cr2O7, 0.5% for NiSO4 and 2% for TiCl4, respectively. A sensitive mouse lymph node assay (SLNA) also determined NiSO4 and K2Cr2O7 as a sensitizer. In the SLNA, TiCl4 caused mild lymph node responses, but was classified as a non-sensitizer as well as ZrCl4. Considering these results, the order of sensitization potential was K2Cr2O7 > NiSO4 > ZrCl4. NiSO4- and K2CrO7-sensitized animals did not show any reactions to ZrCl4 and TiCl4. No cross-reaction among these metal salts was found.

Incubation with IgE increases cholinergic neurotransmission in human airways in vitro

Airway cholinergic hyperresponsiveness is frequently observed in asthmatic patients. Recent reports suggest the possible involvement of IgE in hyperresponsiveness, although the exact mechanism is still uncertain. In this study, we examined whether incubation with IgE could facilitate the cholinergic function in human airways. Bronchi were obtained from 20 patients undergoing lung resection. Cholinergic contractile responses were induced by electrical field stimulation (EFS) or exogenous acetylcholine (ACh), and they were assessed by isometric tension measurement. EFS-induced ACh release from cholinergic nerves was also measured by high performance liquid chromatography. Incubation with IgE significantly enhanced EFS-induced bronchial contraction and ACh release as compared with the values of the bronchi incubated with heat inactivated IgE (control) (p < 0.05, respectively), but it did not alter the contractile responses induced by exogenous ACh. Pretreatment with the muscarinic M2-receptor agonist pilocarpine reduced the EFS-induced ACh release in the control tissues (p < 0.05), but not in the tissues incubated with IgE. The M2-receptor antagonist methoctramine significantly enhanced the EFS-induced contraction in control bronchi (p < 0.05), but this augmentation was not observed in the tissues incubated with IgE. These results suggest that IgE itself can enhance cholinergic bronchial contraction via facilitation of ACh release from cholinergic nerves and that this augmentation is related to autoreceptor M2 dysfunction at nerve endings.

Hypothalamic cholinergic activity associated with 2-deoxyglucose-induced hyperglycemia

In order to clarify the role of the hypothalamic cholinergic system in the regulation of peripheral glucose metabolism, we investigated hypothalamic cholinergic activity after administration of 2-deoxyglucose (2-DG). Intravenous administration of 2-DG (500 mg/kg) caused marked hyperglycemia; the level of plasma glucose increased by 2.1 times over the initial levels at 20 min. For evaluation of the cholinergic activity, we analyzed extracellular levels of acetylcholine (ACh) and choline using brain microdialysis, as well as measuring their tissue levels in the ventromedial hypothalamic nucleus (VMH) and lateral hypothalamus (LH) of rats killed by microwave. In the microdialysis perfusate, extracellular levels of ACh and the metabolite choline were increased by 2-DG administration. In the tissue, a dose dependent decrease in the ACh content and a corresponding increase in the choline content were observed in both hypothalamic nuclei 20 min after administration of 2-DG. These data show that cholinergic activity is increased after 2-DG administration. Both the plasma glucose increment and the fluctuation of ACh and choline content were reduced in pentobarbital anesthetized rats. In 6-hydroxydopamine (6-OHDA) pretreated rats, the hypothalamic content of norepinephrine (NE) was reduced to one-third of that in controls, but there was no significant effect on the hyperglycemia or increase in hypothalamic tissue choline levels following 2-DG. Our results suggest the involvement of the hypothalamic cholinergic system in 2-DC-induced hyperglycemia.

Application of sensitive mouse lymph node assay for detection of contact sensitization capacity of dyes

A sensitive mouse lymph node assay (SLNA) is a test method for the detection of contact allergens. The sensitization potential of test chemicals is determined by assessing total lymph node activation response induced by application of the chemical. In this study, we examined whether the SLNA would have a sufficient competence for determination of sensitization capacity of coloured chemicals routinely. Prior to this study, we investigated application of an Alamar Blue dye (non-radioisotope reagent) as an alternative to [3H]thymidine for measurement of cell proliferation. However, the Alamar Blue assay is useful for determining cell number but is not applicable to detect lymph node cell proliferation activity for 24-h culture in the SLNA. The SLNA was applied to evaluate the sensitization capacity of 20 dyes. Most of the sensitizing dyes were correctly determined as a sensitizer. Some chemicals that were known as strong sensitizers showed strong lymph node responses. Comparing the results of the SLNA with data from guinea-pig tests, the same predictions of sensitization capacity were made in nine out of ten cases. The SLNA also detected 13 of the 17 chemicals that were identified to be contact allergens by the human patch test. These data showed that the evaluation of the SLNA was not influenced by the colour property of the test chemicals and that the SLNA was a sufficiently sensitive robust screen test for the identification of contact allergens.

Application of a novel, plastic formed carbon as a precolumn packing material for the liquid chromatographic determination of acetylcholine and choline in biological samples

A novel carbon material, plastic formed carbon (PFC), was prepared by mixing various amounts of pure graphite with an organic binder and pyrolysing the mixture to a "glassy carbon" at a modest final temperature of 1000-1400 degrees C. This preparation procedure allows more convenient and precise control of the final graphite adsorption characteristics. Various PFC materials were constructed and tested both as bulk adsorbents and as precolumn packings for the direct determination of ACh and Ch in brain tissue homogenates. The PFC precolumns prepared from 12.5-50% graphite, by mass, were capable of selectively removing interfering species while not adsorbing any of the desired quaternary amine analytes. The usually large solvent front was also dramatically reduced with these precolumns. These PFC precolumns are useful for the direct determination of ACh and Ch in brain tissue homogenates and other biological samples.

Cognitive function in rats with alcohol ingestion

The effect of alcohol ingestion on learning disturbances was tested in rats. Rats were fed either an alcohol solution or a nonalcohol solution. The concentration of acetylcholine in the whole brain was significantly lower in rats fed with alcohol than rats fed without alcohol. Passive avoidance learning shows a lower tendency in rats with alcohol compared to rats without alcohol, but the alcohol and control groups did not differ in passive avoidance learning. We suggest that alcohol may disturb acetylcholine metabolism in the brain.

[Therapeutic effect of IGN-2098, a new antiulcer drug (H2-antagonist), in the ulcer diminishing period against acetic acid-induced gastric ulcer in rats]

The effects of IGN-2098 on the healing process of acetic acid-induced gastric ulcer was investigated in comparison with the other histamine H2-receptor antagonists, famotidine and roxatidine acetate HCl, in rats. Ulcer was induced by the injection of acetic acid solution (20%, 0.05 ml). From the 4th day to 17th day after the ulcer induction, drugs were orally administered twice a day. On the 18th day after the ulcer induction, rats were sacrificed to measure the ulcer index macroscopically and to take pictures of the stomachs. Judging from the photographs, the prominence of ulcer the edge was graded into 4 classes, which showed a significant correlation with the histological amount of connective tissue at the ulcer edge. All drugs accelerated the healing of the ulcer, and the effect of IGN-2098 was the most remarkable. In addition, IGN-2098-treatment exhibited more marked inhibition against the prominence of the ulcer edge as compared with the control group. Based on these results, it is concluded that IGN-2098 may be a useful drug for the clinical treatment of ulcer and that the healing acceleration by IGN-2098 without prominence of the ulcer edge may induce no relapse of the ulcer after healing.

Pentobarbital protects against CA1 pyramidal cell death but not dysfunction of hippocampal cholinergic neurons following transient ischemia

Effects of pentobarbital on the release of acetylcholine (ACh), the area of CA1 pyramidal cell soma and the immunoreactivity of choline acetyltransferase (ChAT) in the hippocampus following ischemia were investigated. Five minute ischemia significantly decreased the KCl-, atropine-induced and basal release of ACh and the area of CA1 pyramidal cell soma in the hippocampus. Moreover, ChAT immunoreactivity, a marker of pre-synaptic terminal survival in the cholinergic neurons, was lowered 14 days after ischemia-recirculation. Although treatment with pentobarbital (50 mg/kg) 30 min before ischemia provided complete protection against hippocampal CA1 pyramidal cell death, pentobarbital failed to improve the decrements of ACh release and the low ChAT immunoreactivity over the test period. Our study thus showed discrepancies between pre-synaptic neurochemical estimation and post-synaptic morphological observation of the effect of pentobarbital on ischemic damage.

Immunohistochemical and neurochemical studies of hippocampal cholinergic neurones after ischaemia

We investigated alterations in cholinergic neurones in the gerbil hippocampus after ischaemia. The cholinergic function of acetylcholine (ACh) release fluctuated over the test period. Choline acetyltransferase (ChAT) immunoreactivity decreased slightly on day 1 and no ChAT immunoreactivity was observed on or after day 4 after ischaemia. Since ChAT immunoreactivity is a marker of cholinergic terminal survival, post-ischaemic cholinergic dysfunction on and after day 4 was accompanied by the destruction of terminals. However, dysfunction of the cholinergic system without destruction of the terminals is possible since mild ischaemia decreases ACh release in spite of retaining intact ChAT immunoreactivity. In the morphological study, delayed neuronal death in the stratum pyramidale was observed from day 4. The present study shows that presynaptic cholinergic dysfunction occurs in the early stage prior to pyramidal cell death.

Cytotoxicity of medical materials sterilized with vapour-phase hydrogen peroxide

A new sterilization system using vapour-phase hydrogen peroxide (VPHP) was recently developed. The cytotoxicity of various medical materials sterilized by the VPHP sterilization system was investigated. After VPHP sterilization, polystyrene, polyurethane (PU8), blend material of silicone and polyurethane (Sil/PU6), poly(methyl methacrylate) (PMMA), fluorosilicone acrylate and poly(2-hydroxyethyl methacrylate) (HEMA) showed strong cytotoxicity, whereas polyethylene and polypropylene did not. Although the cytotoxic potential of most materials is reduced by extension of the aeration time, HEMA and PMMA still retained strong cytotoxicity after 12 h aeration. Addition of catalase to the cell culture eliminated the cytotoxicity of sterilized polystyrene and PU8. Hydrogen peroxide (H2O2) residues remaining in the sterilized materials were determined. Large amounts of H2O2 (5.1-186 micrograms) were detected in HEMA, PU8, Sil/PU6 and PMMA. In contrast, silicone and polyethylene contained low levels of H2O2. The amounts of residual H2O2 in the materials decreased with increasing aeration time, but the elimination rate of H2O2 differed among the test materials. The cytotoxic potential of the VPHP-sterilized materials correlated with the amounts of residual H2O2 present. These results indicated that the cytotoxicity of VPHP-sterilized materials was caused by the residual H2O2. To generalize the developed VPHP sterilization system for various medical devices, it is important to validate the aeration of materials for removal of cytotoxic residuals.

[Twenty-eight days repeated dose toxicity test of N-(fluorodichloromethylthio)phthalimide in rats]

N-(Fluorodichloromethylthio)phthalimide (Fluor-folpet) has been widely used as an anti-mold and anti-bacterial agent. In this study, 28 days repeated-dose oral toxicity study of fluor-folpet was carried out in Slc:Wistar rats. An oral toxicity study for fluor-folpet, the twenty-eight days test, repeated-dose, oral administration, was performed as follows: Five week-old rats, male and female, 10 rats, each/group, were treated with intragastric administration of fluor-folpet with a dose of 0 (1% Sodium CMC, control), 20, 80 and 320 mg/kg, body weight. Recovery test, for 14 days after the last treatment, was examined for the control and the 320 mg/kg groups. The 320 mg/kg groups, both males and females, showed significantly reduced their body-weight gain compared with the control group. In the 320 mg/kg group, five out of 20 male rats and four out of 20 female rats died from dyspnea during the treatment period. In the female rats in the 320 mg/kg group, serum ChE level was decreased to 50% of control level and gamma-GT was increased in a dose-dependent manner, but these serum levels recovered after 14 days non-treatment period. No histopathological change, relating to the treatment, in liver was observed. Increased weight of the kidney and vacuolation in renal tubules were found in both sexes of 320 mg/kg group. Hyperkeratosis and hyperplasia of the stomach epithelium were observed at the dose more than 80 mg/kg in male, and more than 20 mg/kg in female. A supplemental study, repeated-dose, oral administration in rats carried out to examine the dyspnea revealed that severe acute toxic damages in epithelium of nasal cavity and meatus nasopharyngeus were induced by intragastric administration of fluor-folpet. Fluor-folpet is shown to be cytotoxic. In conclusion, the no-observed-effect level (NOEL) for fluor-folpet was not found under the experimental conditions employed in this repeated-dose toxicity study.

Recipient-derived T cells participate in autoimmune-like hepatic lesions induced by graft-versus-host reaction

Autoimmune-like hepatic lesions were induced by injection of CD4+ T cells from B10.Thy-1.1 mice into MHC class II-disparate (B10.Thy-1.1 x bm12)F1 mice. Hepatic lesions characterized by mononuclear cell accumulation in the portal area of the central vein and around interlobular bile ducts were observed in these recipients. The morphologic features of the lesions resembled primary biliary cirrhosis. The origin of T cells invading at the site of the hepatic lesions was immunohistochemically analyzed. It was shown that many recipient-derived T cells were present at the lesions and that some of them infiltrated the bile duct epithelia. Furthermore, the lesions were weakened when recipient-type T cells were depleted by thymectomy and the administration of anti-Thy-1.2 monoclonal antibody. Recipient-derived T cells were observed to take part in the formation of autoimmune hepatic lesions. These findings suggest the possibility that the tolerance of self-reactive T cells is abrogated by the graft-versus-host reaction.

Decrease of norepinephrine and preservation of acetylcholine in the hypothalamus of VMH obese rats

We investigated to find which types of neuronal disturbance in the hypothalamus are responsible for ventromedial hypothalamic nucleus (VMH) lesion-induced development of obesity. We found that in VMH-lesioned obese rats, the contents of norepinephrine (NE) and dopamine in the hypothalamus were selectively decreased, but that the serotonin and acetylcholine levels were unchanged from those in sham controls. Also, the content of NE in the lateral portion of the hypothalamus was decreased. Our results show that disturbance of the hypothalamic noradrenergic and dopaminergic neurons, but not of the serotonergic or cholinergic neurons, contributes to the development of VMH lesion-induced obesity.

Studies on the tumor-promoting activity of additives in biomaterials: inhibition of metabolic cooperation by phenolic antioxidants involved in rubber materials

For the detection of tumor-promoting activities of phenolic antioxidants, the inhibitory activities on the intercellular gap-junctional communication were investigated using the V79 metabolic cooperation (MC) assay. Among eight antioxidants, 4,4'-butylidene-bis(3-methyl-6-tert-butyl-phenol), 2,2'-methylene-bis(4-methyl-6-tert-butylphenol) (MBMBP), and styrenated phenol (SP) showed stronger inhibitory activities than lithocholic acid, which is known to be a tumor promotor. However, 4,4'-thio-bis(3-methyl-6-tert-butylphenol), Irganox 1010, and 1330 did not inhibit at any concentrations. When the single-electron oxidation potentials were compared among antioxidants, the electrochemical ease estimated with the first oxidation potential was correlated with the cytotoxic potentials (r = 0.88), but not with the inhibitory activities in an MC assay. The tumor-promoting activity of MBMBP was also investigated using an in vitro, two-stage Balb/c 3T3 transformation assay. MBMBP did not show initiating activity, but significant promoting activity at concentrations of both 1 and 2.5 micrograms/ml were noted. These concentrations were close to the lowest effective inhibitory concentration (1.3 micrograms/ml) of MBMBP in an MC assay. In conclusion, there is a possibility that the phenolic antioxidants that show inhibitory activities in an MC assay contribute to the enhancement of tumor incidence induced by biomaterials.

Studies on the tumor-promoting activities of additives in biomaterials: inhibition of metabolic cooperation by additives such as pigments and phenolic antioxidants

The inhibitory activities on the intercellular gap-junctional communication were investigated using the V79 metabolic cooperation (MC) assay for the detection of tumor-promoting activities of additives such as pigments and phenolic antioxidants. Among six pigments, four chemicals showed inhibitory activities. The inhibitory potencies were ranked in the following order: sudan I > purple 201 > blue 204 > green 202. Sudan I and purple 201 showed stronger inhibitory activities than lithocholic acid, which is known to be a tumor promotor. However, quinizarine and red 225 did not inhibit at any concentration. Relating to eight phenolic antioxidants, four chemicals also showed inhibitory activities. Combining the present findings with previous ones, there are many factors that have tumor-promoting activities via inhibitory action on gap-junctional intercellular communication in biomaterials.

Increase of hypothalamic cholinergic activity in 2-deoxyglucose hyperglycemia

Under inducement of hyperglycemia by intravenous administration of 2-deoxyglucose (2-DG), the contents of choline and acetylcholine (ACh) in the ventromedial hypothalamic nucleus (VMH), lateral hypothalamus (LH) and paraventricular nucleus (PVN) were analyzed after a microdissection of the microwave treated brains. After the administration of 2-DG, the content of choline in those hypothalamic nuclei increased markedly, and the ACh decreased in both the LH and the PVN. The increment of plasma glucose was reduced in the adrenodemedullectomized rats, and simultaneously the increment of the choline in the LH further augmented. These results suggest the contribution of hypothalamic cholinergic neurons in 2-DG-induced hyperglycemia.

Hypothalamic cholinergic and noradrenergic neurons in hyperglycemia induced by 2-deoxyglucose

To investigate the contribution of the hypothalamic cholinergic and noradrenergic neurons in 2-deoxyglucose (2-DG) induced hyperglycemia, we after microwave irradiation analyzed the contents of the neurotransmitters and the metabolites in the microdissected hypothalamic nucleus, ventromedial hypothalamic nucleus (VMH), paraventricular nucleus (PVN) and lateral hypothalamus (LH). A dose dependent decrease in the acetylcholine (ACh) content and a corresponding increase in the choline content was observed in those hypothalamic nuclei 20 min after intravenous administration of 250 or 500 mg/kg 2-DG. The norepinephrine content decreased in 500 mg/kg 2-DG group but did not change significantly in the 250 mg/kg group. These results suggest the involvement and importance of the hypothalamic cholinergic system in 2-DG induced hyperglycemia and, furthermore, that the hyperglycemic response can not be solely attributed to the noradrenergic system.

Assessment of contact sensitivity of four thiourea rubber accelerators: comparison of two mouse lymph node assays with the guinea pig maximization test

Contact sensitivity of four thiourea rubber accelerators, diphenylthiourea (DPTU), dilaurylthiourea (DLTU), dibutylthiourea (DBTU) and diethylthiourea (DETU), was evaluated by a new sensitive mouse lymph node assay (SLNA) and the murine local lymph node assay (LLNA). The results of the SLNA and LLNA were compared with the data of the guinea pig maximization test (GPMT). In the LLNA and SLNA, the sensitizing activity was measured as a function of draining lymph node activation following application of the test chemicals. Of these four thioureas, three (DETU, DBTU and DPTU) were not classified as skin sensitizers in the LLNA. The SLNA successfully detected the sensitivity of all thioureas tested. This result indicated that the SLNA was, in these cases, more sensitive than the LLNA for identification of contact allergens. The order of sensitization potential observed from the SLNA was DPTU (greatest), DLTU, DBTU and then DETU (least). The predictions of sensitizing potential and the order of the sensitizing capacity of four thioureas by the SLNA and the GPMT are very similar.

Nicotine improves cognitive disturbance in senescence-accelerated mice

Senescence-accelerated mice (SAM), a murine model of age-related deterioration in learning ability, were studied as to the acetylcholine (ACh) contents in the brain tissues and the effect of nicotine administration. We found that the ACh content of SAM-P/8 (accelerated senescence-prone) mice was lower than that of SAM-R/1 (accelerated senescence-resistant) mice in the midbrain thalamus and the hypothalamus. In addition, an IP administration of nicotine was found to improve learning ability of SAM-P/8 as shown by performance of a passive avoidance task. Nicotine may potentiate cognitive function in SAM-P/8.