Biomedical subjects

P H Wu

Publications and source records attributed to P H Wu.

At least 19 recordsLinked to original sources

PubMed2006

Synaptic GABAergic and glutamatergic mechanisms underlying alcohol sensitivity in mouse hippocampal neurons.

This study was designed to examine the neuronal mechanisms of ethanol sensitivity by utilizing inbred short sleep (ISS) and inbred long sleep (ILS) mouse strains that display large differences in sensitivity to the behavioural effects of ethanol. Comparisons of whole-cell electrophysiological recordings from CA1 pyramidal neurons in hippocampal slices of ISS and ILS mice indicate that ethanol enhances GABAA receptor-mediated inhibitory postsynaptic currents (GABAA IPSCs) and reduces NMDA receptor-mediated excitatory postsynaptic currents (NMDA EPSCs) in a concentration- and strain-dependent manner. In ILS neurons, these receptor systems are significantly more sensitive to ethanol than those in ISS neurons. To further examine the underlying mechanisms of differential ethanol sensitivities in these mice, GABAB activity and presynaptic and postsynaptic actions of ethanol were investigated. Inhibition of GABAB receptor function enhances ethanol-mediated potentiation of distal GABAA IPSCs in ILS but not ISS mice, and this blockade of GABAB receptor function has no effect on the action of ethanol on NMDA EPSCs in either mouse strain. Thus, subregional differences in GABAB activity may contribute to the differential ethanol sensitivity of ISS and ILS mice. Moreover, analysis of the effects of ethanol on paired-pulse stimulation, spontaneous IPSC events, and brief local GABA or glutamate application suggest that postsynaptic rather than presynaptic mechanisms underlie the differential ethanol sensitivity of these mice. Furthermore, these results provide essential information to focus better on appropriate target sites for more effective drug development for the treatment of alcohol abuse.

Animals↗

PubMed2004

Ionic pair complexes with well-separated columnar stack structure based on [Pt(mnt)2]- ions showing unusual magnetic transition: syntheses, crystal structures, and magnetic properties.

Three ion pair complexes, [4-R-benzylpyridinium][bis(maleodinitriledithiolato)platinum(III)] (abbreviated as [RBzPy][Pt(mnt)(2)]; R = Cl (1), Br (2), or NO(2) (3)), have been synthesized. The cations and anions stack into well-separated columns in the solid state, and the Pt(III) ions form a 1-D zigzag chain within a [Pt(mnt)(2)](-) column through Pt...S, S...S, and Pt...S...Pt interactions. The chain is uniform in 1 and 2, while it alternates in 3. Unusual magnetic phase transitions from paramagnetism to diamagnetism were observed in these three complexes at approximately 275 K for 1, approximately 269 K for 2, and approximately 184 K for 3. These phase transitions were also found in DSC measurements for 1 and 2. The overall magnetic behaviors for 1-3 indicate the presence of antiferromagnetic exchange interactions in the high-temperature phase and spin-gapped systems in the low-temperature phase. Below 50 K, 2 exhibits weak ferromagnetism. The spontaneous moments are nearly repressed by a field of 1.0 T. The crystal structure of 2 at 173 K reveals that there are two crystallographically independent [Pt(mnt)(2)](-) entries in an asymmetric unit. These two crystallographically independent [Pt(mnt)(2)](-) entries satisfy the spin-canting condition, and the EPR spectra measured at room temperature exhibit anisotropic character. Therefore, the weak ferromagnetic behavior in the low-temperature region for 2 can be attributed to the spin-canting phenomenon.

Journal Article↗

PubMed2001

2-Methyl-1-(4-nitrobenzyl)pyridinium bis(maleonitriledithiolato)nickelate(III).

In the title complex, 2-methyl-1-(4-nitrobenzyl)pyridinium bis(1,2-dicyanoethene-1,2-dithiolato)nickelate(III), (C(13)H(13)N(2)O(2))[Ni(C(4)N(2)S(2))(2)], the most prominent general structural feature of the complex is the completely segregated columnar stacks of anions and cations. Within the cation column, there may be stacking interactions between adjacent nitro groups and benzene rings.

Journal Article↗

PubMed2001

Terahertz responses of intrinsic Josephson junctions in high T(c) superconductors.

High frequency responses of intrinsic Josephson junctions up to 2.5 THz, including the observation of Shapiro steps under various conditions, are reported and discussed in this Letter. The sample was an array of intrinsic Josephson junctions singled out from inside a high T(C) superconducting Bi2Sr2CaCu2O(8+x) single crystal, with a bow-tie antenna integrated to it. The number of junctions in the array was controllable, the junctions were homogeneous, the distribution of applied irradiation among the junctions was even, and the junctions could synchronously respond to high frequency irradiation.

Journal Article↗

PubMed2001

Chronic ethanol exposure results in increased acute functional tolerance in selected lines of HAFT and LAFT mice.

RATIONALE AND OBJECTIVES: Functional (pharmacodynamic) ethanol tolerance can be evidenced within a single session of exposure to ethanol (acute or within-session tolerance), or after repeated ethanol exposures (chronic or between-session tolerance). To investigate whether acute and chronic tolerance to ethanol are inter-related phenomena, the effect of chronic ethanol exposure was evaluated in mice selectively bred for high (HAFT) or low (LAFT) acute functional tolerance to an ataxic effect of ethanol, i.e., loss of balance on a stationary dowel. METHODS: Mice were tested for sensitivity (threshold ethanol concentration for loss of balance on the stationary dowel) and acute functional tolerance to ethanol before and after a regimen of chronic ethanol exposure (twice-daily ethanol injections for 6 days). RESULTS: Chronic ethanol treatment did not alter the threshold for ethanol's ataxic effect (i.e., produced no change in sensitivity). However, this treatment, in a dose-dependent manner, resulted in an increase in the magnitude and rate of development of acute functional tolerance. CONCLUSIONS: This finding supports previous postulates that chronic ethanol tolerance can be characterized by a more rapid acquisition or a greater magnitude of acute (within-session) tolerance. However, the increase in acute tolerance that occurred after chronic ethanol exposure was similar in both selected lines of mice, indicating little or no genetic correlation between acute tolerance and chronic tolerance.

Alcoholic Intoxication↗

PubMed2000

New alkaloids from Annona purpurea.

Three new alkaloids, promucosine (1), romucosine F (2), and romucosine G (3), along with 28 known compounds, were isolated from the MeOH extract of stems of Annona purpurea. The structures of 1-3 were determined on the basis of spectral data and chemical evidence.

Alkaloids↗

PubMed2000

Overexpression of type 7 adenylyl cyclase in the mouse brain enhances acute and chronic actions of morphine.

The mechanisms by which morphine-induced analgesia and tolerance and physical dependence on morphine arise have been the subject of intense study, and much work has pointed to the involvement of cAMP-mediated events in the neuroadaptive phenomena leading to morphine tolerance and/or dependence. We overexpressed an opioid receptor-stimulatable form of adenylyl cyclase (type 7) in the central nervous system of mice and demonstrated significant effects of this manipulation on the animals' acute response to morphine, the development of morphine tolerance, and development of sensitization to morphine. Measurements of the acute analgesic response to morphine demonstrated that the ED(50) values for the transgenic mice were significantly lower than the ED(50) values determined for the "wild-type" animals. During chronic treatment with morphine, the transgenic mice developed tolerance more rapidly than the wild-type mice, and transgenic animals of the C57BL/6xSJL background showed a larger sensitization to morphine's effects on locomotor activity than did wild-type mice of the same background. These results indicated that cAMP-generating systems may simultaneously modulate the development of tolerance and sensitization. Interestingly, the signs of physical dependence on morphine in the transgenic mice did not differ from those in their wild-type litter mates, indicating that separate mechanisms may modulate opiate tolerance and opiate dependence.

Adenylyl Cyclases↗

PubMed1999

Differential increase in Fos immunoreactivity in hypothalamic and septal nuclei by arginine8-vasopressin and desglycinamide9-arginine8-vasopressin.

Subcutaneous or intracerebroventricular injection of either arginine8-vasopressin or desglycinamide9-arginine8-vasopressin has been shown to facilitate memory, reduce or reverse the effects of amnesic drugs, and maintain tolerance to some effects of ethanol. These actions of vasopressin (and, by inference, of desglycinamide9-arginine8-vasopressin) are mediated by vasopressin V1 receptors in brain, via a c-fos-dependent mechanism, but the receptors at which the desglycinamide analog acts have not been identified. The precise central sites are also not known, but evidence of several types suggested the anterior hypothalamus and septum as probable loci of vasopressin action. In the present work, this question was studied by immunocytochemistry, using antibodies against Fos and Fos-like proteins. The numbers of Fos-immunoreactive nuclei were counted in several related brain regions and structures, after administration of arginine8-vasopressin, des-Gly9-[Arg8]-vasopressin or saline. A subcutaneous injection of vasopressin, but not of saline, enhanced Fos expression in the paraventricular, supraoptic and suprachiasmatic nuclei of the hypothalamus, but the desglycinamide analog stimulated Fos expression only in the suprachiasmatic nucleus. Vasopressin injection significantly increased the number of Fos-immunoreactive cells in the intermediate lateral septum, medial septum, and dorsal and ventral divisions of the lateral septum. In contrast, the desglycinamide analog increased the numbers of Fos-immunoreactive cells in the dorsal and intermediate portions of the lateral septum, but caused no change in the medial septum, and a decrease in the ventral portion of the lateral septum. Increased Fos expression was also found in the subfornical organ after subcutaneous injection of either vasopressin or the desglycinamide analog. Double labeling with antibodies against Fos protein and against vasopressin revealed that most of the vasopressin-induced Fos-immunoreactive cells in the supraoptic, paraventricular and suprachiasmatic hypothalamic nuclei are also vasopressin immunoreactive, i.e. they are vasopressin-producing neurons. These findings suggest that a circuit involving V1 receptors in the subfornical organ, connecting fibres to the suprachiasmatic nucleus, and vasopressinergic projections from the suprachiasmatic nucleus to the lateral septum, may play a central role in mediating the actions of both vasopressin and its desglycinamide analog in the maintenance of ethanol tolerance.

Animals↗

PubMed1997

Simultaneous gas chromatographic determination of methamphetamine, amphetamine and their p-hydroxylated metabolites in plasma and urine.

We report a method for the simultaneous determination of methamphetamine, amphetamine and their hydroxylated metabolites in plasma and urine samples using a GC-NPD system. The analytical procedures are: (1) adjust the sample to pH 11.5 with bicarbonate buffer, saturate with NaCl and extract with acetate; (2) back-extract the amines in the ethyl acetate fraction with 0.1 M HCl; (3) adjust the pH of the acid fraction to 11.5 and follow by extraction in ethyl acetate; (4) reduce the volume of ethyl acetate under nitrogen and derivatize the concentrate with trifluoroacetic anhydride or heptafluorobutyric anhydride before the GC analysis. The derivatives were separated on a GC-NPD system equipped with a HP-5 column of 25 m x 0.32 m I.D. and a 0.52 micron film of 5% phenylmethylsilicone. The detection limit (taking a signal-to-noise ratio of 2) of heptafluorobutyl derivatives of methamphetamine and its metabolites in plasma and the trifluoroacetyl derivatives in urine was 1 ng/ml (22 pg on column). The limit of quantitation of the heptafluorobutyl derivatives in the plasma was 1 ng/ml (22 pg on column), and that of the trifluoroacetyl derivatives in urine was 20 ng/ml (73 pg on column). The between-day variation was from 0.9 to 17.4% and within-day variation from 0.9 to 8.3%. This method was used successfully in the quantitative determination of methamphetamine and its p-hydroxylated metabolites in the plasma and urine of human subjects.

Amphetamine↗

PubMed1996

Dizocilpine prevents the development of tolerance to ethanol-induced error on a circular maze test.

Dizocilpine [(+)MK-801] and ketamine, in doses that disrupt learning and memory, also prevent the development of tolerance to the motor impairing effects of ethanol (EtOH). However, dizocilpine itself affects motor behavior. In order to separate the possible influence of these two effects on the development of tolerance to EtOH, food-reinforced performance on a circular maze test was used in two different experiments. EtOH alone (1.2 g/kg) tended to increase the error score and reduce number of runs per trial, running speed, and total distance run, but on chronic administration of EtOH, tolerance developed progressively to all these effects. Dizocilpine also increased the error score, but had a biphasic effect on measures of running: low and intermediate doses (0.009 and 0.075 mg/kg, IP) increased running distance, whereas a high dose (0.15 mg/kg) decreased running speed and distance. When combined with EtOH, dizocilpine tended to overcome the effect of EtOH on running activity, but not on error score. Chronically, dizocilpine (0.075 and 0.15 mg/kg) prevented the development of tolerance to the effect of EtOH on error score, even though the lower dose of dizocilpine permitted tolerance to the effects of EtOH on running. These results suggest that NMDA receptor antagonists selectively inhibit tolerance to cognitive effects of ethanol even when the antagonists do not affect motor performance.

Animals↗

PubMed1996

Development of alcohol tolerance in the rat after a single exposure to combined treatment with arginine8-vasopressin and ethanol.

A single i.c.v. injection of 100 ng of AVP, followed 30 min later by an i.p. injection of EtOH (1.8 g/kg) and three 2-min trials of motor-impairment testing on a moving belt, resulted in the development of tolerance to this effect of EtOH, that lasted up to 4 weeks. The rate of tolerance loss was not altered by daily injection of a V1 receptor antagonist, but pretreatment with a V1 receptor antagonist or cycloheximide prevented this AVP facilitation of the development of tolerance to EtOH-induced motor impairment. The destruction of serotonin neuronal terminals by i.c.v. injection of 5,7-dihydroxytryptamine also prevented the development of tolerance after a single exposure to AVP + EtOH, but the destruction of catecholamine terminals by i.c.v. injection of 6-hydroxydopamine did not prevent such tolerance. In contrast to the findings with motor impairment, no tolerance to EtOH-induced hypothermia and loss of righting reflex developed after a single combined AVP-EtOH treatment. The tolerance that develops after one treatment with AVP-EtOH is a functional rather than a dispositional tolerance, and shares many pharmacological properties with chronic tolerance to EtOH.

Animals↗

PubMed1995

Peripheral injection of arginine8-vasopressin increases Fos in specific brain areas.

Learned behaviors and tolerance to ethanol can be maintained by peripheral injection of arginine8-vasopressin (vasopressin) under conditions in which they would otherwise be lost. However, the sites of this action in the brain have not been clearly identified. Using a polyclonal antibody raised against Fos and Fos-like proteins, we have demonstrated increases in immunoreactive Fos and Fos-like proteins in the suprachiasmatic, supraoptic and paraventricular nuclei of the hypothalamus, and lesser increases in piriform cortex and amygdala, of the rat 2 h after a s.c. injection of vasopressin. Our results suggest that the exogenous vasopressin may exert its central action by activating a cellular immediate early gene in specific brain regions.

Animals↗

PubMed1994

The identification of NP25: a novel protein that is differentially expressed by neuronal subpopulations.

A novel gene encoding a 25-kDa neuronal-specific protein, here named 'NP25', has been isolated as a cDNA clone from rat brain. The sequence of the NP25 cDNA reveals a single open reading frame that encodes a primary translation product of 206 amino acids. A search of the protein sequence databank indicates that NP25 is significantly homologous with three recently discovered muscle proteins: SM22 alpha, mp20 and calponin. The gene is specifically and ubiquitously expressed in the rat brain and has conserved sequences among chicken, rat, mouse and human. Rat brain NP25 was identified by Western blot using an antiserum elicited against trpE-NP25 fusion protein. On pH gradient electrophoresis, NP25 was separated into at least two isoforms with similar molecular weights. Immunocytochemistry and in situ hybridization demonstrated that NP25 was differentially expressed by neuronal subpopulations of the rat central nervous system. The highest concentration of NP25 protein was localized in central amygdaloid nuclei and glomeruli in the granule layer of cerebellum. The wide and differential distribution of NP25 in the brain suggests that it may play a particular important role in the function of specific neuronal systems.

Amino Acid Sequence↗

PubMed1994

Formation and electrophysiological actions of the arachidonic acid metabolites, hepoxilins, at nanomolar concentrations in rat hippocampal slices.

Metabolites of arachidonic acid are known to be formed in the mammalian central nervous system. When intact hippocampal slices were incubated in artificial cerebrospinal fluid, 12-hydroxyeicosatetraenoic acid and two isomers of hepoxilin A3 (8R and 8S) were released as measured by gas chromatography-mass spectrometry. These compounds were released in greater amounts in the presence of noradrenaline or when arachidonic acid was added to the slices. The neuronal actions of chemically derived preparations of 8R and 8S hepoxilins and the glutathione conjugate, hepoxilin A3-C, were examined using intracellular and whole-cell electrophysiological recordings in hippocampal CA1 neurons in vitro. All compounds had the excitatory effects of lowering spike threshold and decreasing spike frequency adaptation, and the inhibitory actions of membrane hyperpolarization, enhanced postspike train afterhyperpolarizations and increased inhibitory postsynaptic potentials or currents. A synthetic analog of hepoxilin A3-C, in which the glutathione moiety is placed at carbon position 9 instead of carbon position 11 as in hepoxilin A3-C, was inactive. The actions of the hepoxilins showed a sharp dose-response relationship, with minimal threshold or no effect at 3 nM (n = 21) and maximal effects at 10 nM (n = 33). There were no significant differences between the responses to either the 8R or 8S isomers, or between hepoxilin A3 and hepoxilin A3-C. These data suggest that hepoxilins formed by the brain have significant neuromodulatory actions.

2-Amino-5-phosphonovalerate↗

PubMed1994

Selective involvement of central 5-HT2 receptors in the maintenance of tolerance to ethanol by arginine8-vasopressin.

Arginine8-vasopressin (AVP) has been shown repeatedly to affect learning and memory and to maintain tolerance to ethanol if the brain serotonin and catecholamine systems are intact. In the present study, 5,7-dihydroxytryptamine (5,7-DHT) was injected intracerebroventricularly to disrupt serotonergic projections from the raphe to the forebrain. This resulted in a marked decrease in 5-hydroxytryptamine (5-HT) immunoreactivity in the terminal areas of the septum and the hippocampus, but not in the serotonin-containing neuronal cell bodies in the raphe nuclei. In control rats, tolerance to the motor-impairing effects of ethanol lasted for only 5 days after the cessation of ethanol treatment but could be maintained indefinitely for as long as AVP was given. In the 5,7-dihydroxytryptamine-lesioned rats, AVP was unable to maintain the tolerance. Continuous intracerebroventricular infusion of 5-HT restored the ability of AVP to maintain ethanol tolerance in the lesioned rats. A selective 5-HT2 agonist (alpha-methylserotonin) was equally effective, and a 5-HT3 receptor agonist (2-methylserotonin) was slightly less effective, but the 5-HT1A agonist dipropylaminotetralin (8-hydroxy-dipropylaminotetralin) was totally ineffective in this respect. The results indicate selective involvement of brain 5-HT2 and possibly 5-HT3 receptors in mediating AVP maintenance of tolerance to ethanol but do not pinpoint their specific loci or roles.

5,7-Dihydroxytryptamine↗

PubMed1993

GABA and pentobarbital potentiation of chloride influx into microsacs is influenced by incubation time.

GABA-mediated chloride influx into rat cerebral cortical microsacs, and its potentiation by pentobarbital (PB), was studied in incubations lasting 50 or 3000 ms. The 3000 ms assays were carried out manually, while the 50 ms assays were performed in a quench flow machine. The EC50 of the GABA effect and the Hill coefficient were both lower at the longer incubation times. Percent increase of the effect of GABA (at EC30 concentration) by pentobarbital was greater in the 3000 ms than in the 50 ms incubations. Preincubation of microsacs with PB for 5 s before the 50 ms incubation with GABA, did not increase the effect of PB beyond that obtained by adding PB into the incubation only. This finding is consistent with earlier ones cited, which imply that only PB binding that occurs after GABA has bound can potentiate the effect of GABA, and suggests that the concentrations of PB and GABA required to enhance chloride influx in vivo may be higher than those commonly reported in the literature.

Animals↗

PubMed1993

An Alu sequence interrupts a human 5-hydroxytryptamine1D receptor pseudogene.

Molecular cloning studies have now identified six HTR genes encoding the biosynthesis of the structurally homologous human serotonin (5-hydroxytryptamine; 5-HT) receptors, namely 5-HTR1A, 5-HTR1B, 5-HTR1C, 5-HTR1D, 5-HTR2 and 5-HTRS31. Several of these receptors are encoded by intronless genes, and we now report the cloning of another intronless serotonergic HTR gene. This gene was cloned by a method using the polymerase chain reaction. The nucleotide sequence of this gene is most closely homologous to the 5-HTR1D gene; however, several stop codons, frame shifts and deletions are present in the coding region suggesting that this is a pseudogene which could not encode a functional receptor. Sequence analysis also revealed that the coding sequence of this pseudogene is disrupted by insertion of a 283-bp Alu repeat sequence.

Amino Acid Sequence↗

PubMed1993

Blockade of chronic tolerance to ethanol by the NMDA antagonist, (+)-MK-801.

Previous studies indicated that learning and memory play important roles in the development of tolerance to ethanol. (+)-MK-801 has been shown to impair learning and might thus also block the development of tolerance to ethanol. To test this possibility, rats were trained to criterion on the moving belt, a complex motor coordination test. Acute i.p. injection of (+)-MK-801 (a non-competitive NMDA channel blocker) produced dose-related impairment on this test. A dose of 0.1 mg/kg, that had negligible effect by itself, potentiated the acute effects of ethanol. In a chronic experiment with different animals, half of the rats received (+)-MK-801 or saline daily, followed 30 min later by ethanol (1.8 g/kg i.p.) and three practice runs on the belt, and 1 h later a second dose of (+)-MK-801 or saline. The other half received the same drugs but ethanol followed the practice. (+)-MK-801 blocked the functional tolerance to ethanol in both groups when the pre-ethanol dose was 0.25 mg/kg, but not when it was 0.1 mg/kg. Tolerance to the effects of (+)-MK-801 itself did not occur over 2 weeks of treatment. These results suggest that NMDA receptors are involved in development of chronic tolerance to ethanol as shown previously with rapid tolerance.

Animals↗