Chun Fu Wu

Determination of endogenous acetylcholine release in freely moving rats by transstriatal dialysis coupled to a radioenzymatic assay: effect of drugs.

Abstract: The technique of intracerebral dialysis in combination with a sensitive and specific radioenzymatic method was used for recovery and quantification of endogenous extracellular acetylcholine from the striata of freely moving rats. A thin dialysis tube was inserted transversally through the caudate nuclei, and the tube was perfused with Ringer solution, pH 6.1, at a constant rate of 2 μl min−1. The perfusates were collected at 10‐min intervals. In the presence of 1 and 10 μM physostigmine, acetylcholine release was 4.5 ± 0.02 and 7.3 ± 0.3 pmol/10 min, respectively (not corrected for recovery). The latter concentration of the acetylcholinesterase inhibitor was used in all experiments. Under basal conditions, acetylcholine output was stable over at least 4 h. A depolarizing K+ concentration produced a sharp, reversible 87% increase in acetylcholine output. Both the basal and K+‐stimulated release were Ca2+ dependent. The choline uptake inhibitor hemicholinium‐3 (20 μg intracerebroventricularly) reduced striatal acetylcholine output to 35% of the basal value within 90 min. Scopolamine (0.34 mg/kg s.c.) provoked a sharp enhancement of acetylcholine release of ∼63% over basal values, whereas oxotremorine (0.53 mg/kg i.p.) transiently reduced acetylcholine release by 54%. These results indicate the physiological and pharmacological suitability of transstriatal dialysis for monitoring endogenous acetylcholine release.

Sex difference in psychological behavior changes induced by long-term social isolation in mice

Social isolation can induce psychological behavior changes. It is interesting to know whether there is sex difference in responding to social isolation or not. The present study compared the behavior difference between male and female mice isolated for 1-4 months. The results showed that the isolated male mice had higher accounts of locomotor activity than the isolated female and group-housed ones. Both isolated male and female mice spent shorter time in the dark box than the group-housed mice in the light/dark test, and isolated male mice spent less time in the closed arms than isolated female and group-housed mice when isolated for 2, 3 and 4 months in the elevated plus-maze test. These results suggest that isolation induce an anxiolytic-like effect. The immobile time in the forced swimming test was shortened in male mice isolated for 1 and 2 months. Both isolated male and female mice showed shorter time in pentobarbital-induced loss of righting reflex and less body weight gain. These results demonstrated that there was a sex difference in psychological behavior changes in mice undergoing social isolation and the male mice were more easily affected by isolation.

RV09, a novel resveratrol analogue, inhibits NO and TNF-α production by LPS-activated microglia

Excessive activation of microglial cells has been implicated in various neurodegenerative diseases. Resveratrol, a polyphenolic compound found in grapes and wine, has been reported to reduce the activation of microglia. In the present study, 5-[2-(4-bromothiophen-2-yl)vinyl]benzene-1,3-diol (RV09), a novel resveratrol analogue, was found to suppress NO production by LPS-activated N9 microglial cell line and/or cultured rat cortical microglia. RV09 appeared to have a slight NO-scavenging activity in sodium nitroprusside (SNP) solution. The inhibition of iNOS was also observed, suggesting the blockage of transcriptional levels. Moreover, RV09 attenuated the expression of mRNA and protein of tumor necrosis factor-alpha (TNF-alpha) in a concentration-dependent manner. Further studies revealed that RV09 blocked IkappaBalpha phosphorylation and degradation, as well as reactive oxygen species (ROS) production in N9 microglial cells. It was also found that RV09 is a effective scavenger for 2,2-diphenyl-1-picrylhydrazyl (DPPH) used as a general free radical model. In the summary, these data suggest that, by blocking IkappaBalpha phosphorylation and degradation, RV09 acts to suppress the LPS-induced NO and TNF-alpha production in microglia, and this effect was mediated, at least in part, by inhibiting the generation of ROS. Our results suggested that RV09 is a novel anti-inflammatory agent which can inhibit proinflammatory responses of microglia.

Morphine decreases extracellular levels of glutamate in the anterior cingulate cortex : an in vivo microdialysis study in freely moving rats

In the present study, we investigated the effect of morphine on the extracellular levels of glutamate in the anterior cingulate cortex (ACC) in freely moving rats using in vivo microdialysis coupled to high performance liquid chromatography and electrochemical detection. The results showed that either acute or chronic morphine treatment decreased the extracellular levels of glutamate in the ACC. Naloxone could reverse the decrease induced by chronic morphine treatment. The present study provided the first neurochemical evidence that morphine decreased extracellular levels of glutamate in the ACC, suggesting that glutamate in ACC is involved in the central actions of morphine.

Effects of clozapine, olanzapine and haloperidol on nitric oxide production by lipopolysaccharide-activated N9 cells.

Schizophrenia is a devastating illness of unknown etiology and the basis for its treatment rests in the symptomatic response to antipsychotics. It was found that some of the patients with schizophrenia elicited microglia activation. The present study used lipopolysaccharide (LPS)-activated mouse microglial cell line N9 as an in vitro model to mimic microglia activation seen in the patients with schizophrenia. The effects of clozapine, olanzapine and haloperidol on the release of nitric oxide (NO) by LPS-stimulated N9 cells were investigated. The results showed that olanzapine significantly inhibited NO release by LPS-stimulated N9 cells. Clozapine and haloperidol did not show significant effects on this model. The present study suggested that the inhibiting effect of olanzapine on the NO release by LPS-stimulated microglial cells might be a new mechanism through which olanzapine exhibits its therapeutic effect in the treatment of schizophrenia.

Protective effects of pseudoginsenoside-F11 on methamphetamine-induced neurotoxicity in mice

In the present study, pseudoginsenoside-F(11) (PF(11)), a saponin that existed in American ginseng, was studied on its protective effect on methamphetamine (MA)-induced behavioral and neurochemical toxicities in mice. MA was intraperitoneally administered at the dose of 10 mg/kg four times at 2-h intervals, and PF(11) was orally administered at the doses of 4 and 8 mg/kg two times at 4-h intervals, 60 min prior to MA administration. The results showed that PF(11) did not significantly influence, but greatly ameliorated, the anxiety-like behavior induced by MA in the light-dark box task. In the forced swimming task, PF(11) significantly shortened the prolonged immobility time induced by MA. In the appetitively motivated T-maze task, PF(11) greatly shortened MA-induced prolonged latency and decreased the error counts. Similar results were also observed in the Morris water maze task. PF(11) significantly shortened the escape latency prolonged by MA. There were significant decreases in the contents of dopamine (DA), 3,4-dihydroxyphenacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindoacetic acid (5-HIAA) in the brain of MA-treated mice. PF(11) could partially, but significantly, antagonize MA-induced decreases of DA. The above results demonstrate that PF(11) is effective in protection of MA-induced neurotoxicity and also suggest that natural products, such as ginseng, might be potential candidates for the prevention and treatment of the neurological disorders induced by MA abuse.

Comparison of inhibitory potency of three different curcuminoid pigments on nitric oxide and tumor necrosis factor production of rat primary microglia induced by lipopolysaccharide

Microglia are the resident innate immune cells in the central nervous system. Evidence supports that the unregulated activation of microglia results in the production of pro-inflammatory cytokines and chemokines that propagate neuronal injury and finally cause neurodegenerative diseases. Curcuminn (Cur), demethoxycurcumin (DMC), and bisdemethoxycurcumin (BDMC) are curcuminoid pigments extracted from turmeric (Curcuma longa L.). Cur has been reported to suppress the activation of microglia by reducing toxic factors production, but little is known about whether the two natural demethoxy derivatives of Cur, DMC and BDMC, have the similar effects as Cur. In the present study, we found that all of the three curcuminoid pigments significantly suppressed nitric oxide (NO) production by LPS-activated microglia and the relative potency was DMC>BDMC>Cur. This result was verified by RT-PCR analysis of iNOS mRNA. The NO-scavenging abilities of three curcuminoid pigments are very weak, which suggested that the indirect effect may not be critical in inhibiting NO production by LPS-activated microglia. Moreover, these three curcuminoid pigments attenuated the expression of mRNA and proteins of tumor necrosis factor-alpha (TNF-alpha) in a concentration-dependent manner and the relative potency was also DMC>BDMC>Cur. In conclusion, Cur, DMC and BDMC were found as potent microglia-activation inhibitors, and DMC exhibited the strongest inhibitory activity on NO and TNF-alpha production. These results provided an interesting clue for designing new compounds which could have better potential therapeutic implications for various neurodegenerative diseases.

Differential effects of haloperidol, clozapine and olanzapine on learning and memory functions in mice

Many schizophrenic patients exhibit impairments in neurocognitive functions. Typical antipsychotic drugs such as haloperidol, have limited or even detrimental influence on cognitive functions. In contrast, atypical antipsychotic drugs, such as clozapine and olanzapine, may improve memory function in schizophrenics. However, only a few studies have been conducted to directly compare the effects of olanzapine, clozapine and haloperidol on memory functions in animal models. Thus, their effects on this issue were investigated in the present studies by using one-way step-through passive avoidance task and Morris water maze as models of learning and memory. The results showed that olanzapine did not affect acquisition, consolidation or retrieval process in step-through test. Moreover, it improved spatial learning function in mice in Morris water maze task. Clozapine and haloperidol appeared to impair acquisition process and consolidation process, respectively, in step-through test. Both drugs impaired spatial learning function in mice in Morris water maze task. The results suggested a positive implication for the clinical medication of olanzapine in schizophrenic treatment.

Anxiolytic-like effects of oleamide in group-housed and socially isolated mice.

Oleamide (cis-9,10-octadecenoamide) is an endogenous sleep-inducing lipid and prototypic member of a new class of biological signaling molecules identified in recent years. In the present study, the anxiolytic-like effect of oleamide was studied in several experimental models of anxiety in group-housed and socially isolated mice. As the results show, socially isolated mice exhibited an anxiogenic-like profile in the elevated plus-maze test, the light/dark test, and the hole-board test, which could be significantly reversed by oleamide (10 or 20 mg/kg, i.p.). Moreover, oleamide significantly reduced the anxiety levels in grouped-housed mice. In the isolation-induced aggressive test, oleamide markedly reduced the attacking duration and increased the attacking latency. It is concluded that oleamide has an anxiolytic-like effect in socially isolated or group-housed mice, which suggests that fatty acid amides might be involved in the regulation of anxiety-related behavior in mice.

Pseudoginsenoside-F11 decreases morphine-induced behavioral sensitization and extracellular glutamate levels in the medial prefrontal cortex in mice

Morphine produces a variety of behavioral and biochemical changes related to its abuse. Our previous studies showed that Pseudoginsenoside-F11 (PF11), an ocotillol-type saponin existing in American ginseng, can antagonize pharmacological effects of morphine. To further investigate the effects of PF11 on morphine abuse and the underlying mechanisms, we tested the effects of PF11 on morphine-induced development of behavioral sensitization and alterations in glutamate levels in the medial prefrontal cortex (mPFC) in freely moving mice by using in vivo microdialysis. As the results shown, PF11 antagonized the development of behavioral sensitization and decrease of glutamate in the mPFC induced by morphine. Therefore, these findings suggest that PF11 may block the development of morphine-induced behavioral sensitization via its effect, at least partially, on the glutamatergic system in the mPFC.