M100907, a selective 5-HT2A receptor antagonist and a potential antipsychotic drug, facilitates N-methyl-D-aspartate-receptor mediated neurotransmission in the rat medial prefrontal cortical neurons in vitro

The technique of intracellular recording was used to examine the effect of M100907 (formerly MDL 100907), a highly selective 5-HT2A receptor antagonist and a potential antipsychotic drug (APD), on N-methyl-D-aspartate (NMDA) and (+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor-mediated responses in pyramidal cells of the rat medial prefrontal cortex in in vitro brain slice preparations. Bath administration of M100907, but not its inactive stereoisomer M100009, produced a 350% to 550% increase of NMDA-induced responses in a concentration-dependent manner with an EC50 value of 14 nmol/L, reminiscent of the action of clozapine. M100907 did not alter AMPA responses. Moreover, M100907 significantly increased the amplitude and duration of excitatory postsynaptic potentials and currents evoked by electrical stimulation of the forceps minor. We have generated several lines of evidence indicating that M100907 enhances glutamate receptor-mediated neurotransmission in pyramidal cells of the medial prefrontal cortex by facilitating NMDA-induced release of excitatory amino acids. The robust potentiation of NMDA receptor-mediated neurotransmission may explain, at least partly, the potential antipsychotic action of this compound. Furthermore, if M100907 proves to be an effective APD and if our findings can be extended to other atypical APDs, which are known to possess a relatively high affinity to 5-HT2A receptors, they may account for the purported efficacy of atypical APDs in alleviating some negative symptoms such as cognitive and executive functions.

Exaggerated precocious centromere separation in cells of a human breast cancer line treated with a green tea extract

In a breast cancer cell line, MDA-MB-468, established in our laboratory, an average of 3% of the mitotic cells exhibited a phenomenon known as centromere splaying, which is a characteristic feature of cells of patients with Roberts syndrome. However, centromere splaying in cells of Roberts syndrome patients is limited to i) the centromere region and ii) chromosomes with large amounts of heterochromatin. When the breast cancer cells were treated with an extract of green tea GTE-TP91, up to 45% of the metaphases were observed to exhibit this behavior; and the precocious centromere separation was highly exaggerated, affecting all chromosomes in such metaphases. Apparently, as the sister centromeres continued to pull apart, they carried the chromatids with them, except for the telomere regions, giving a ring-like configuration. Eventually, the sister chromatids became completely separated. Whether this bizarre phenomenon was induced by the polyphenols contained in this green tea extract GTE-TP91 is not known, but this phenomenon, upon further investigation, may throw some light on chromosomal proteins, centromere behavior, telomere behavior and related questions.

Chromosomal aberrations induced by 12C6+ heavy ion irradiation in spermatogonia and spermatocytes of mice

The testes of Kun-Ming strain mice were radiated with different doses of 12C6+ ion or 60Co gamma-ray. Chromosomal aberrations induced in spermatogonia and spermatocytes were analyzed by the air-drying method. The relative biological effectiveness (RBE) of 12C6+ ion was calculated with respect to 60Co gamma-ray for the induction of chromosomal aberrations. The 12C6+ ion and 60Co gamma-ray dose-response relationships for chromosomal aberrations were plotted by linear quadratic models. The results showed that there was an increase in frequency of chromosomal aberrations in all the treated groups compared to controls. The RBE values were 1.67 for aberrations of spermatogonia and 1.66 for aberrations of spermatocytes for a dose of 2.0 Gy. Moreover, a different distribution of the various types of aberrations has been found for 12C6+ ion and 60Co gamma-ray irradiations. The dose-response relationships for 12C6+ ion and 60Co gamma-ray exhibited negative curvature in both spermatogonia and spermatocytes groups: the frequencies of aberrations increased sharply at low doses and exhibited less sharp increases for higher doses, which may be related to an interaction between the chromosomal damage and a block in cell cycle. Our results may provide useful information for the assessment of genetic risks of humans exposed to heavy ions.

M100907, a highly selective 5-HT2A receptor antagonist and a potential atypical antipsychotic drug, facilitates induction of long-term potentiation in area CA1 of the rat hippocampal slice

In the present study, we have shown that M100907, a highly selective 5-HT2A receptor antagonist and a putative atypical antipsychotic drug (APD), markedly potentiates N-methyl-D-aspartate (NMDA) responses and excitatory postsynaptic currents (EPSCs) evoked by electrical stimulation of the Schaffer collaterals in CA1 hippocampal pyramidal cells. Furthermore, it enhances the induction of long-term potentiation (LTP) of CA1 synapses. If our findings can be extended to other atypical APDs, which are known to possess a relatively high affinity to 5-HT2A receptors, they may account for the purported efficacy of atypical APDs in alleviating some negative symptoms and improving cognitive and executive functions. In addition, the possibility of using M100907 as a nootropic should be further tested.

Pediatric gamma hydroxybutyrate intoxication

Reported are 2 uncommon cases of childhood gamma hydroxybutyrate (GHB) toxicity and the surreptitious manner in which GHB was made. Two children unintentionally ingested a soft drink containing GHB and were found comatose. Both had been well 1 hour earlier. The parent had made GHB by combining gamma butyrolactone with caustic soda (sodium hydroxide). Symptoms were early in onset and resolved in 24 hours. The ECG changes in one case are unique to GHB toxicity and are unexplained. GHB-toxic children appear similar to adults who have this poisoning. Supportive management remains the mainstay of therapy. Health care providers should be aware of GHB's clandestine production and its increasing presence on the streets and in the home. This agent is not detected with common drug screens.

Mycoplasma genitalium infection and host antibody immune response in patients infected by HIV, patients attending STD clinics and in healthy blood donors

Prevalence of Mycoplasma genitalium in humans is still not clear. We have developed a sensitive and specific serological assay for M. genitalium using lipid-associated membrane proteins (LAMPs) as antigens. Antibodies to LAMPs from M. genitalium showed little cross-reactivity to LAMPs from antigenically similar M. pneumoniae. For validity testing, urines from 104 patients were tested by PCR for M. genitalium. All 15 PCR+ patients had M. genitalium-LAMPs antibodies. Moreover, none of 64 antibody-negative patients were PCR+. Serological study of 1800 patients of various diseased groups and healthy blood donors showed M. genitalium was primarily a sexually transmitted microbe that infected patients with AIDS (44.0%), intravenous drugs users with or without HIV infection (42.5%), and also HIV- patients attending STD clinics (42.6%). Only 5.5% HIV- healthy blood donors and 1.3% HIV+ hemophiliacs tested positive. M. genitalium has been associated with acute non-gonococcal urethritis in male patients. However, many sexually active men and women appear to be chronically infected or colonized by the microbe without apparent clinical symptoms and may continue to transmit the organism through sexual contacts.

[The analysis of schizophrenic inpatients' escape behavior]

To study the escaping behavior of 1030 schizophrenic in-patients, "Brief Rating Scale for Dangerous Behavior of In-patient" was used to asses them within their first week hospitalization from May 1994 to March 1996. The result showed that 276 (26.8%) patients had escaping behavior. The patients with paranoid schizophrenia had higher rate of escaping behavior. There was no correlation being found between sex, age, duration of illness, and escaping behavior. The patients with the history of such behavior were more likely to escape from ward (41.9%). The suggestion for preventing such behavior were discussed.

Mycoplasma genitalium infection and host antibody immune response in patients infected by HIV, patients attending STD clinics and in healthy blood donors

Prevalence of Mycoplasma genitalium in humans is still not clear. We have developed a sensitive and specific serological assay for M. genitalium using lipid-associated membrane proteins (LAMPs) as antigens. Antibodies to LAMPs from M. genitalium showed little cross-reactivity to LAMPs from antigenically similar M. pneumoniae. For validity testing, urines from 104 patients were tested by PCR for M. genitalium. All 15 PCR+ patients had M. genitalium-LAMPs antibodies. Moreover, none of 64 antibody-negative patients were PCR+. Serological study of 1800 patients of various diseased groups and healthy blood donors showed M. genitalium was primarily a sexually transmitted microbe that infected patients with AIDS (44.0%), intravenous drugs users with or without HIV infection (42.5%), and also HIV- patients attending STD clinics (42.6%). Only 5.5% HIV- healthy blood donors and 1.3% HIV+ hemophiliacs tested positive. M. genitalium has been associated with acute non-gonococcal urethritis in male patients. However, many sexually active men and women appear to be chronically infected or colonized by the microbe without apparent clinical symptoms and may continue to transmit the organism through sexual contacts.

Clozapine and haloperidol modulate N-methyl-D-aspartate- and non-N-methyl-D-aspartate receptor-mediated neurotransmission in rat prefrontal cortical neurons in vitro

The effects of the antipsychotic drugs haloperidol and clozapine on N-methyl-D-aspartate (NMDA) and non-NMDA receptor-mediated neurotransmission were examined and compared in pyramidal cells of the medial prefrontal cortex in rat brain slices by using the techniques of intracellular recording and single-electrode voltage-clamp. The bath administration of either haloperidol or clozapine produced a marked facilitation (300-400%) of NMDA-evoked responses in a concentration-dependent manner. The EC50 values of haloperidol and clozapine were 38 and 14 nM, respectively. At concentrations of > or =100 nM, clozapine, but not haloperidol, produced bursts of excitatory postsynaptic potentials (EPSPs), which were blocked by glutamate receptor antagonists, suggesting that these EPSPs were the result of increasing release of excitatory amino acids. Haloperidol, but not clozapine, produced a concentration-dependent inhibition of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-induced current with an EC50 value of 37 nM. Haloperidol significantly decreased the amplitude of EPSPs evoked by the electrical stimulation of the forceps minor, whereas clozapine increased the amplitude of these EPSPs. The study of current-voltage relationship indicates that clozapine preferentially potentiates NMDA receptor-mediated transmission, whereas haloperidol depresses the non-NMDA receptor-mediated response, which probably obscures its potentiating effect on NMDA receptor-mediated EPSPs.

NMDA-induced response in pyramidal neurons of the rat medial prefrontal cortex slices consists of NMDA and non-NMDA components

Using the techniques of intracellular recording, we examined and characterized the membrane response induced by N-methyl-D-aspartate (NMDA) and compared the excitatory postsynaptic potentials (EPSPs) elicited by NMDA and by electrical stimulation of the forceps minor in presumed pyramidal cells of the rat medial prefrontal cortex (mPFC) slice preparation. Bath application of NMDA produced EPSPs, membrane depolarization, and bursts of action potentials. These effects were completely blocked by the NMDA receptor antagonist D-2-amino-phosphonopentanoic acid (d-AP5). The non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dion (CNQX) markedly decreased NMDA-induced responses and converted the I-V relationship curve of NMDA from a curvi-linear to the characteristic J-shape, thus indicating the existence of a non-NMDA component. Synaptic responses elicited by electrical stimulation of the forceps minor also consisted of NMDA and non-NMDA components. Both NMDA- and electrical stimulation-elicited EPSPs were markedly reduced or completely abolished by using Ca2+-free artificial cerebrospinal fluid (ACSF), ACSF containing either TTX, low Ca2+ plus Cd2+, or a membrane permeable Ca2+ chelator BAPTA-AM (when BAPTA was loaded in the recording electrode, it was without effect). Under these conditions, NMDA-induced depolarization was significantly reduced. Taken together, these results suggest that in addition to a direct action on pyramidal neurons, NMDA causes a release of excitatory amino acids (EAAs), which in turn activate non-NMDA receptors.

Antidotal efficacy of glutamate and aspartate for colchicine toxicity

Glutamic and aspartic acids were evaluated for their antidotal efficacy in colchicine toxicity. Female adult inbred mice were treated with ip doses of either 1000 mg glutamic acid (GA) or aspartic acid (AA)/kg bw by various treatment schedules relative to the administration of an ip LD5n of 7.8 mg colchicine/kg bw. Mice were observed for survival and changes in body weight. Pretreatment with AA increased survival by 42% (p = 0.01). Concurrent AA treatment improved survival non-significantly (p = 0.07). With post-exposure AA therapy, however, mortality was increased (p = 0.005). No significant beneficial effects of GA occurred. Early AA therapy improves survival in colchicine poisoned mice, but as delay in treatment is increased, AA efficacy is lost.

Potyvirus transmission is not increased by pre-acquisition fasting of aphids reared on artificial diet

Aphids (Myzus persicae), fasted after removal from healthy rearing plants, transmitted tobacco etch potyvirus (TEV) more efficiently than unfasted aphids whether virus acquisition was from infected leaves or through membranes. There was no difference in uptake of 125I-labelled TEV by fasted or unfasted aphids as measured by liquid scintillation counting. When aphids acquired 125I-labelled TEV, label was retained in the stylets (as determined by autoradiographic light microscopy) by 51 % of 272 fasted aphids, as against 7.8% of 258 unfasted aphids. There was a close correlation between virus transmission by aphids and virion retention in stylets. The effect of pre-acquisition fasting disappeared when aphids reared on an artificial diet were used in virus transmission tests. The transmission rates obtained with such aphids were similar to the rates with fasted aphids reared on healthy plants. Our results support the hypothesis that fasting eliminates plant component(s) which interfere with the retention of virions in the food canal of aphid stylets.

Pharmacological actions of the atypical antipsychotic drug clozapine: a review

Clozapine [8-chloro- 11-(4-methyl- 1-piperazinyl)-3H-dibenzo (b,e)(1,4) diazepine], or clozaril, is a member of the dibenazepine class of antipsychotic drugs. Initially, studies in animals using a number of neurochemical, biochemical, electrophysiological, and behavioral paradigms indicated that clozapine was markedly different from various typical antipsychotic drugs such as haloperidol and chlorpromazine. Subsequently, clinical studies have shown that clozapine is effective in ameliorating the core symptoms, as well as the negative symptoms, in schizophrenia. However, clozapine has a much lower propensity for inducing neurological side effects after acute or repeated administration compared to various typical neuroleptics. Furthermore, clozapine is therapeutically effective in treating about 30% of schizophrenic patients who are resistant to standard antipsychotic drugs. Based on the above information, clozapine has been designated an atypical antipsychotic drug. However, at this time, it is not entirely clear why clozapine is such a unique antipsychotic drug. To date, there has not been a comprehensive review regarding clozapine's pharmacological profile. Therefore, we will review clozapine's profile in the following areas: 1) affinity for neurotransmitter receptors in the brain; 2) electrophysiology (in vivo, single-cell recording and iontophoresis; in vitro studies); 3) in vivo microdialysis and voltammetry; 4) monoamine turnover or metabolism; 5) intermediate early gene expression; 6) positron emission tomography studies; and 7) molecular biological studies. We will also compare and contrast clozapine's acute and chronic effects, and discuss the merits of various hypotheses that have been put forward to explain clozapine's unique profile.

Effect of aging on erythropoietin secretion in male rats

The secretion of erythropoietin (EPO) and testosterone in response to hypoxia in old (22-25 months), middle (mid)-aged (15-17 months), adult (6-7 months), and young (3 months) male rats was studied. Rats of different ages were bled by cardiac puncture before and subsequent to 8 h exposure to 12% O2. The metabolic clearance rate of EPO was determined by a single-injection method. The effects of orchidectomy and replacement of testosterone propionate on plasma EPO concentrations were also investigated. Analysis of the direct effects of testosterone on EPO release from kidney tissue was carried out in an in vitro study. Both basal and hypoxia-induced EPO levels were lower in old rats than in mid-aged, adult, and young rats (p < .01). Plasma testosterone levels decreased in response to hypoxia in all rats (p < .01 for young, adult, and mid-aged rats, and p < .05 for old rats). The old rats also had lower plasma testosterone levels following hypoxia when compared with other rats (p < .05). The metabolic clearance rate of EPO was not affected by age. Orchidectomy decreased rat plasma EPO concentration (p < .05). This decrease could be restored to intact levels after testosterone propionate replacement. Both 10(-10) M (p < .05) and 10(-9) M (p < .01) testosterone stimulate EPO release from kidney tissue in vitro. Our findings indicate that the basal levels of plasma EPO and testosterone are decreased, and the hypoxia-induced EPO is also diminished with aging in male rats. These data suggest that the mechanism of tolerance to hypoxia and the endocrine function of the kidneys in male rats during the aging process are testosterone-dependent.

Translocations and deletions of 5q13.1 in myelodysplasia and acute myelogenous leukemia: evidence for a novel critical locus

Acquired partial and complete deletions of chromosome 5 (5q-, -5) are common cytogenetic anomalies associated with myelodysplasia (MDS) and acute myeloid leukemia (AML). A critical region of consistent loss at 5q31.1 (in > 90% of cases) has led us and others to postulate the presence of a key negative regulator(s) of leukemogenesis. Although the interstitial deletion limits vary among patients, del(5) (q13q33) and del(5)(q13q35) constitute major subsets. Furthermore, it is not rare to encounter deletions, translocations, or paracentric inversions involving 5q11 to 5q13, which indicates inactivation or disruption of important gene(s) at that locus. In this report, we have localized a novel locus at 5q13.1 to a 2.0-Mb interval between the anonymous markers D5S672 and GATA-P1804. This locus resided within the region of loss in 12 of 27 patients with anomalies of chromosome 5; one of these cases had apparent retention of both alleles of all the telomeric loci. Fluorescence in situ hybridization (FISH) studies demonstrate that the AML cell line ML3 is disrupted at 5q13.1 by a translocation involving chromosome 3, with apparent retention of the entire chromosome 5 sequence. Our results suggest that this novel proximal locus encodes a critical gene that may be deleted or disrupted in a subset of MDS/AML patients with chromosome 5 anomalies.

5-HT3-like receptors in the rat medial prefrontal cortex: further pharmacological characterization

The aim of the study was to further characterize the pharmacological properties of 5-hydroxytryptamine (5-HT)3-like receptors in the rat medial prefrontal cortex (mPFC) using combinations of biochemical and electrophysiological approaches. Phenylbiguanide (PBG) and three chlorinated derivatives, ortho-chloro-PBG (oCPBG), meta-chloro-PBG (mCPBG) and para-chloro-PBG (pCPBG), dose-dependently stimulated phosphoionositide (PI) turnover in fronto-cingulate cortical slices. All three chloro-isomers of PBG were equipotent in stimulating PI turnover. SR 57227A ((4-amino)-(6-chloro-2-pyridyl) L-piperidine hydrochloride, a novel compound with high affinity and selectivity for peripheral and central 5-HT3 receptors) dose-dependently stimulated PI turnover in fronto-cingulate cortical slices. The rank order of potency of all the 5-HT3 receptor agonists tested in the PI assay as compared to 5-HT was: 5-HT > 2-Me-5-HT > SR57227A > PBG = mCPBG = oCPBG = mCPBG. 5-HT and 5-HT receptor agonists depressed the firing rate of both spontaneously active and glutamate-activated quiescent mPFC cells in a current (dose)-dependent fashion. The rank order of effectiveness of these compounds was: 5-HT > SR57227A = 2-Me-5-HT = mCPBG = oCPBG = pCPBG = PBG. Unlike its action on the 5-HT3 receptors in the periphery or cultured cell lines, D-tubocurarine chloride appears to be non-specific in blocking the depressant action of 2-Me-5-HT, gamma-aminobutyric acid and dopamine. Our results combined support the view that the pharmacological properties of 5-HT3-like receptors in the mPFC are not identical to those located in peripheral tissues and in cultured cell lines.

Encephalopathy and cranial nerve palsies caused by intentional trichloroethylene inhalation

This report describes an acute intentional trichloroethylene exposure that developed neurological and cardiovascular toxicity. The patient presented with palsies of the third, fifth, and sixth cranial nerves. Clinical manifestations, laboratory values, and treatment plans are discussed. Emergency physicians should be aware of the complications of trichloroethylene exposure and consider the diagnosis in patients with similar symptoms.

Trisomy 7 by dual-color fluorescence in situ hybridization: a potential biological marker for prostate cancer progression

Smear preparations from fine-needle aspirates of 30 prostatic carcinomas obtained from radical prostatectomy specimens were examined by a dual-color fluorescence in situ hybridization (FISH) method for the presence of chromosome 7 trisomy (chromosome 9 was used as a control). The frequency of cells with trisomy 7 was determined in tumor cells and normal prostatic epithelial cells in each specimen. Comparison between the tumor and normal cells from the same patients showed that within all stages, the frequency of trisomy 7/disomy 9 cells in the tumor cells was significantly higher than that observed in the normal cells (P < 0.0001). Furthermore, the mean frequency of cells with trisomy 7/disomy 9 in advanced stages was significantly elevated over the mean frequency observed in organ-confined tumors (P = 0.02). These results are consistent with our previous data on paraffin-embedded prostate tissue sections using single-color FISH procedures. However, the method used in the present study enhances the accuracy of distinguishing trisomic 7 cells from potentially triploid (trisomy 7/trisomy 9) cells. Furthermore, the use of fine-needle aspirates rather than paraffin sections provides an easy method to examine whole nuclei. Our study also suggests that FISH provides a better measure of genetic instability (e.g., aneuploidy) in prostate tumors than flow cytometry.

Loss of potyvirus transmissibility and helper-component activity correlate with non-retention of virions in aphid stylets

The hypothesis that loss of aphid transmissibility of potyvirus mutants is due to non-retention of virions in the mouthparts was tested by feeding aphids through membranes on purified virions of aphid transmissible (AT or HAT) and non-aphid-transmissible (NAT) tobacco vein mottling virus (TVMV) or tobacco etch virus (TEV), in the presence of functional [potato virus Y (PVY) HC or TVMV HC] or non-functional (PVC HC) helper component (HC). TVMV virions were detected, by electron microscopic examination of immunogold-labelled thin sections, in the food canal or cibarium of 57% of 28 aphids fed on the transmissible combination of TVMV-AT and functional HC, while no virions were found in these structures in 25 aphids fed on the non-transmissible combinations: TVMV-NAT and PVY HC, or TVMV-AT and PVC HC. Autoradiography of intact stylets allowed the examination of much larger numbers of aphids, fed on 125I-labelled TEV; 48% of 523 aphids fed on the TEV-HAT and PVY HC combination retained label in the stylets: this correlated well with the percentage transmission in bioassays. In contrast, in non-transmissible combinations, label was found in the stylets of 0.77% of 389 aphids fed on TEV-NAT and PVY HC, and 1.35% of 223 aphids fed on TEV-HAT and PVC HC. No differences were found in the overall amount of label in the bodies of aphids fed on the transmissible and non-transmissible combinations. There was a strong tendency for virions to be retained in the distal third of the stylets; 56% of aphids positive for TVMV, and 82% of those positive for TEV, had label in this area. These data support the concept that virions retained within the stylets are those that are primarily involved in potyvirus transmission.

Identification of a murine CD4+ T-lymphocyte response site in hepatitis C virus core protein

The T cell response to a recombinant HCV truncated core protein (cp1-10) was measured in a proliferation assay. Based on a 10-fold greater response to this truncated core protein than to its shorter form (cp1-8), a predominant epitope was mapped to the carboxyl quarter of this sequence. This epitope was further mapped to a synthetic peptide corresponding to amino acids 121-140 of the core protein. The peptide was antigenic for T cells of all three H-2 types tested, H-2 r, b and d, and the proliferating T cells were CD4+. Besides inducing specific proliferation in vitro, peptide aa121-140 can prime helper T cells in vivo. When boosted with core protein, mice primed with peptide produced 64-fold higher antibody titer than without priming in 1 week. The identification of a broadly immunogenic T cell helper epitope on core protein may be important for vaccine design against HCV.

Examination of the action of 3,4-methylenedioxymethamphetamine on rat A10 dopamine neurons

Extracellular single cell recording was used to examine the effect of intravenous administration of (-), (+), and (+/-)-3,4-methylenedioxymethamphetamine (MDMA) on A10 dopamine (DA) neurons in chloral hydrate anesthetized male rats. Both (+/-)-MDMA and (+)-MDMA inhibited the firing rate of most (79%) A10 DA cells. By contrast, (-)-MDMA induced either no effect or a slight increase in the firing rate of these cells. Analysis of the effects of (+/-)-MDMA on the firing pattern of the DA cells revealed on overall decrease in the percentage of spikes in bursts but both increases and decreases were seen in the coefficient of variation of interspike intervals. To determine the contribution of 5-HT and DA to the (+/-)-MDMA-induced inhibition of A10 DA cells rats were pretreated either with the 5-HT synthesis inhibitor p-chlorophenylalanine (PCPA) or the DA synthesis inhibitor alpha-methyl-p-tyrosine (AMPT). Pretreatment of rats with PCPA did not reduce the ability of (+/-)-MDMA to inhibit the DA cells. However, in rats pretreated with AMPT, the (+/-)-MDMA-induced inhibition was blocked and some cells (44%) showed instead an increase in firing rate following administration of (+/-)-MDMA. The administration of l-3,4-dihydroxyphenylalanine (L-DOPA) to AMPT-treated rats rapidly restored the inhibition of cell firing by (+/-)-MDMA. In conclusion, the results reported here demonstrate that MDMA has an overall inhibitory effect on A10 DA cells. Despite MDMA's greater potency in releasing 5-HT compared to DA, the inhibitory effect of this drug on A10 DA cells appears to be mediated by the latter transmitter.

Codebook organization to enhance maximum a posteriori detection of progressive transmission of vector quantized images over noisy channels

We describe a new way to organize a full-search vector quantization codebook so that images encoded with it can be sent progressively and have resilience to channel noise. The codebook organization guarantees that the most significant bits (MSBs) of the codeword index are most important to the overall image quality and are highly correlated. Simulations show that the effective channel error rates of the MSBs can be substantially lowered by implementing a maximum a posteriori (MAP) detector similar to one suggested by Phamdo and Farvardin (see IEEE Trans. Inform. Theory, vol.40, no.1, p.156-193, 1994). The performance of the scheme is close to that of pseudo-gray coding at lower bit error rates and outperforms it at higher error rates. No extra bits are used for channel error correction.

Modulation of the A10 dopamine system: electrophysiological studies of the role of 5-HT3-like receptors

The distribution of 5-HT3-like receptors is primarily in the mesocorticolimbic structures. We have previously demonstrated that the atypical antipsychotic drug clozapine and a structurally related compound RMI 81,582 differ from other typical antipsychotic drugs in that they are effective 5-HT3 receptor antagonists. Our experimental results suggest that 5-HT3-like receptors play a permissive role in regulating or gating the inhibitory action of dopamine in the mesocorticolimbic areas. We hypothesize that the ability of clozapine to antagonize both 5-HT3-like and dopamine receptors may account for its preferential interaction with the mesocorticolimbic dopamine system and the higher efficacy in treating the schizophrenic symptoms.

Comparison of the action of the stereoisomers of the psychostimulant 4-methylaminorex (4-MAX) on midbrain dopamine cells in the rat: an extracellular single unit study

In this study, we examined and characterized the action of the stereoisomers of 2-amino-4-methyl-delta 2-5-phenyl-oxazoline (4-methylaminorex, 4-MAX) on spontaneously active dopamine (DA) neurons in the substantia nigra pars compacta (SNC or A9) and ventral tegmental area (VTA or A10) in anesthetized male rats. This was accomplished using the technique of extracellular single unit recording. The intravenous (i.v.) administration of the stereoisomers of 4-MAX (0.1-6.4 mg/kg) produced a dose-dependent suppression of the basal firing rate of A10 DA cells with the following rank order of potency: trans 4S,5S > cis 4R,5S approximately cis 4S,5R >> trans 4S,5S 4-MAX. The rank order of potency of the isomers of 4-MAX to suppress the firing of A9 DA cells was trans 4S,5S = cis 4R,5S = cis 4S,5R >> trans 4R,5R. The trans 4S,5S isomer was 5-fold more potent in suppressing DA cell firing in the A10 compared to the A9 area. The suppressant action of the isomers on A9 and A10 DA cells was reversed by the i.v. administration of haloperidol and the D2/D3 receptor antagonists (-)-sulpiride and (-)-eticlopride but not by the D1 receptor antagonists SCH 23390 and SCH 39166. In addition, the suppressant action of the trans 4S,5S isomer on A10 DA cells was not antagonized or reversed by the i.v. administration of the receptor antagonists granisetron (5-HT3), ritanserin (5-HT2A,C), idazoxan (alpha 2), phentolamine (peripheral alpha 1), (+/-)-pindolol (5-HT1A,B beta) or prazosin (alpha 1). The pretreatment of animals with either alpha-methyl-p-tyrosine (AMPT) or reserpine, but not p-chlorophenylalanine (PCPA), (+/-)-fluoxetine or tomoxetine, significantly attenuated the suppression of A10 DA cell firing produced by trans 4S,5S 4-MAX. Overall, our results suggest that the suppressant action of 4-MAX on midbrain DA cell firing may be mediated by the release of DA, which subsequently interacts with D2/D3 receptors.

Calcium channel blocker overdose

A case of diltiazem overdose with significant hemodynamic compromise is presented. Multiple therapeutic modalities were attempted with limited results. Control was finally achieved with a combination of norepinephrine, dobutamine, and cardiac pacing. Invasive pulmonary monitoring parameters are reported and were important in the management of this patient. The management of calcium channel blocker overdose and the various available therapeutic modalities are discussed.