Correction: R-ketamine: a rapid-onset and sustained antidepressant without psychotomimetic side effects.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Maintenance behaviour and long-lasting insecticide-treated nets (LLITNs) previously introduced into Bourapar district, Khammouane province, Lao PDR.

BACKGROUND: Long-lasting insecticide-treated nets (LLITNs) are expected to be an important advance in malaria control, but operational experience is still scarce. This study presents some operational findings concerning the introduction of Olyset LLITNs (Sumitomo Chemical Co., Ltd, Japan) in Laos. The study site, Bourapar district, a remote district at high risk of malaria, received Olyset nets during 1999-2000. After distribution of the nets the number of malaria cases in the district hospital decreased for a time, however it began to rise again a year after the intervention. To sustain the effect of the nets, net users were given instructions on maintenance and use. This study aimed to investigate the condition of Olyset nets and the maintenance behaviour of net users after 2-3 years of use, and to examine the associations between maintenance behaviour and the number of malaria episodes during the previous year. METHODS: Questionnaire interviews and inspections of nets were conducted at 240 households during February-March 2003. RESULTS: About 40% of the observed nets had holes/were torn, and the maintenance instructions had not been followed sufficiently. Households following the recommended washing frequency (38.2%) reported fewer malaria episodes during the past year, which demonstrates the importance of the recommended washing frequency in the effective use of the nets. CONCLUSIONS: Our study promotes the idea that, in addition to pursuing high coverage of LLITNs, more effort should be made to ensure that nets are kept in good condition in future LLITN programmes.

Hippocampal synapsin I, growth-associated protein-43, and microtubule-associated protein-2 immunoreactivity in learned helplessness rats and antidepressant-treated rats.

Learned helplessness rats are thought to be an animal model of depression. To study the role of synapse plasticity in depression, we examined the effects of learned helplessness and antidepressant treatments on synapsin I (a marker of presynaptic terminals), growth-associated protein-43 (GAP-43; a marker of growth cones), and microtubule-associated protein-2 (MAP-2; a marker of dendrites) in the hippocampus by immunolabeling. (1) Learned helplessness rats showed significant increases in the expression of synapsin I two days after the attainment of learned helplessness, and significant decreases in the protein expression eight days after the achievement of learned helplessness. Subchronic treatment of naïve rats with imipramine or fluvoxamine significantly decreased the expression of synapsin I. (2) Learned helplessness increased the expression of GAP-43 two days and eight days after learned helplessness training. Subchronic treatment of naïve rats with fluvoxamine but not imipramine showed a tendency to decrease the expression of synapsin I. (3) Learned helplessness rats showed increased expression of MAP-2 eight days after the attainment of learned helplessness. Naïve rats subchronically treated with imipramine showed a tendency toward increased expression of MAP-2, but those treated with fluvoxamine did not. These results indicate that the neuroplasticity-related proteins synapsin I, GAP-43, and MAP-2 may play a role in the pathophysiology of depression and the mechanisms of antidepressants.

Pregnenolone and dehydroepiandrosterone administration in neonatal rats alters the immunoreactivity of hippocampal synapsin I, neuropeptide Y and glial fibrillary acidic protein at post-puberty.

It is well documented that neurosteroids administered during the neonatal period influence the development of several brain systems. In our previous study, pregnenolone administered to rats during the neonatal period altered adenosinergic and dopaminergic functions in the striatum and cerebral cortex. The present study examined the effects of the treatment with pregnenolone and dehydroepiandrosterone (DHEA) from the postnatal day (P) 3-P7 on synapsin I (a marker for presynaptic terminals) and glial fibrillary acidic protein (GFAP: a marker for astroglia) levels in the hippocampus of Sprague-Dawley rats at 3 and 7 weeks of age. In addition, neuropeptide Y and dynorphin A immunoreactivity was measured. The administration of pregnenolone and DHEA to neonatal rats significantly altered the expression of synapsin I in the dentate gyrus and CA3 region at post-puberty but not at pre-puberty. A significantly greater expression of GFAP-immunoreactive astrocytes or processes was demonstrated in the pregnenolone- and DHEA-treated groups at both pre-puberty and post-puberty. A significant increase in the number and size of GFAP-immunoreactive astrocytes and in the extension of arborization was seen in the overall hippocampus. The number of neuropeptide Y-positive cells in the hilus region was also significantly increased in the neurosteroid-treated group at post-puberty. No differences were detected in dynorphin A immunoreactivity among the experimental groups. These results of this study suggest that pregnenolone and DHEA play an important role in the development of hippocampus.

R-ketamine: a rapid-onset and sustained antidepressant without psychotomimetic side effects.

Although the efficacy of racemate ketamine, a rapid onset and sustained antidepressant, for patients with treatment-resistant depression was a serendipitous finding, clinical use of ketamine is limited, due to psychotomimetic side effects and abuse liability. Behavioral and side-effect evaluation tests were applied to compare the two stereoisomers of ketamine. To elucidate their potential therapeutic mechanisms, we examined the effects of these stereoisomers on brain-derived neurotrophic factor (BDNF)-TrkB signaling, and synaptogenesis in selected brain regions. In the social defeat stress and learned helplessness models of depression, R-ketamine showed a greater potency and longer-lasting antidepressant effect than S-ketamine (esketamine). Furthermore, R-ketamine induced a more potent beneficial effect on decreased dendritic spine density, BDNF-TrkB signaling and synaptogenesis in the prefrontal cortex (PFC), CA3 and dentate gyrus (DG) of the hippocampus from depressed mice compared with S-ketamine. However, neither stereoisomer affected these alterations in the nucleus accumbens of depressed mice. In behavioral tests for side effects, S-ketamine, but not R-ketamine, precipitated behavioral abnormalities, such as hyperlocomotion, prepulse inhibition deficits and rewarding effects. In addition, a single dose of S-ketamine, but not R-ketamine, caused a loss of parvalbumin (PV)-positive cells in the prelimbic region of the medial PFC and DG. These findings suggest that, unlike S-ketamine, R-ketamine can elicit a sustained antidepressant effect, mediated by increased BDNF-TrkB signaling and synaptogenesis in the PFC, DG and CA3. R-ketamine appears to be a potent, long-lasting and safe antidepressant, relative to S-ketamine, as R-ketamine appears to be free of psychotomimetic side effects and abuse liability.

Expression of the cAMP response element binding protein (CREB) in hippocampus produces an antidepressant effect.

BACKGROUND: Recent studies have demonstrated that chronic antidepressant treatment increases the expression of the cyclic amp (cAMP) response element binding protein (CREB) in rat hippocampus. The study presented here was conducted to determine if CREB is a relevant target that produces an antidepressant-like effect. METHODS: We employed the herpes simplex virus (HSV)-mediated gene transfer technique to overexpress CREB and determined its effect on the learned helplessness and forced swim tests, two established models used for pharmacological screening of antidepressant drugs. RESULTS: In the learned helplessness model, rats that received bilateral microinjection of HSV-CREB into the dentate gyrus showed significantly fewer escape failures in the subsequent conditioned avoidance test than those injected with control vector (HSV-LacZ). In contrast, microinjection of HSV-CREB in either the CA1 pyramidal cell layer of hippocampus or the prefrontal cortex did not produce an antidepressant response. In the forced swim test, CREB expression in the dentate gyrus resulted in a significantly shorter immobility time than those injected with HSV-LacZ. CONCLUSIONS: These results demonstrate that over-expression of CREB in hippocampus results in an antidepressant effect and suggest that CREB may serve as a potential molecular target for novel therapeutic agents.

Effects of age and gender on the expression of brain-derived neurotrophic factor mRNA in rat retrosplenial cortex following administration of dizocilpine.

Using in situ hybridization, we studied the effects of age and gender on the expression of brain-derived neurotrophic factor (BDNF) mRNA and heat shock protein hsp-70 mRNA in the rat retrosplenial cortex following administration of the noncompetitive NMDA receptor antagonist (+)-MK-801 (dizocilpine). Male and female Sprague-Dawley rats (5 weeks, 12 weeks, or 10 months old) were given a single intraperitoneal injection of saline (1 ml/kg) or dizocilpine (0.3, 1.0, or 3.0 mg/kg). No expression of BDNF mRNA and hsp-70 mRNA was detected in the rat retrosplenial cortex after administration of saline (1 ml/kg, IP). Administration of dizocilpine (0.3, 1.0, or 3.0 mg/kg, IP) caused a marked induction of BDNF mRNA and hsp-70 mRNA in the retrosplenial cortex of male and female rats, in a dose-dependent manner. Female rats were more sensitive to the induction of BDNF mRNA and hsp-70 mRNA in the retrosplenial cortex by dizocilpine as compared to male rats. It was also found that adult (12 weeks old) and aged (10 months old) rats were more sensitive to the induction of hsp-70 mRNA and BDNF mRNA in the retrosplenial cortex by dizocilpine as compared to young (5 weeks old) rats. These results suggest that the age and gender differences observed in the expression of BDNF mRNA and hsp-70 mRNA in the retrosplenial cortex by dizocilpine may be associated with the differences in dizocilpine-induced neurotoxicity observed with gender and age within the same region.

Adenosine A2A, 5-HT1A and 5-HT7 receptor in neonatally pregnenolone-treated rats.

Steroid hormones synthesized in the brain, called 'neurosteroids', modulate neuronal activity. We treated neonatal rats with a main precursor of the neurosteroidogenesis, pregnenolone, and examined adenosine A2A receptor, 5- hydroxytryptamine (5-HT)1A and 5-HT7 receptor densities in the front-parietal cortex in juvenile and adult rats. In receptor binding assay using [3H]CGS21680 and [3H]8-OH-DPAT, it was shown that neonatal pregnenolone-treatment induced a significant decrease in the adenosine A2A receptor density with no significant effects on the 5-HT1A and 5-HT7 receptor densities.

Reduction of substance P after chronic antidepressants treatment in the striatum, substantia nigra and amygdala of the rat.

We investigated the effects of chronic treatment with food containing one of five antidepressants on substance P (SP) content in the rat brain using radioimmunoassay and enzyme-immunoassay. The antidepressants used were imipramine, desipramine, clomipramine, amoxapine and mianserin. Following 40 days of treatment, all the antidepressants decreased SP concentrations in the striatum, substantia nigra and amygdala. Only imipramine and desipramine reduced the peptide content in the hippocampus, and only mianserin reduced it in the septum. We further examined the acute effects of antidepressants one hour after a single intraperitoneal administration. Acute imipramine and desipramine treatment reduced SP in the striatum, whereas acute mianserin decreased it in the striatum and substantia nigra. These results demonstrate that all antidepressants on chronic treatment had a common effect, a reduction of SP content in the striatum, substantia nigra and amygdala. This raises the possibility that such a decrease may contribute to the therapeutic action of antidepressants in affective disorders.

Behavioral changes and expression of heat shock protein hsp-70 mRNA, brain-derived neurotrophic factor mRNA, and cyclooxygenase-2 mRNA in rat brain following seizures induced by systemic administration of kainic acid.

Kainic acid-induced seizures in rats represent an established animal model for human temporal lobe epilepsy. However, it is well-known that behavioral responses to the systemic administration of kainic acid are inconsistent between animals. In this study, we examined the relationship between expression of genes, neuropathological damage, and behavioral changes (seizure intensity and body temperature) in rats after systemic administration of kainic acid. The considerable differences in the response to kainic acid-induced seizures were observed in rats after a single administration of kainic acid (12 mg/kg i.p.). There was no detection of the expression of heat shock protein hsp-70 mRNA and HSP-70 protein in brain of vehicle-treated controls and in animals exhibiting weak behavioral changes (stage 1-2). A moderate expression of hsp-70 mRNA was detected throughout all regions (the pyramidal cell layers of CA1-3 and dentate gyrus) of the hippocampus, the basolateral, lateral, central and medial amygdala, the piriform cortex, and the central medial thalamic nucleus of rats that developed moderate seizures (stage 3-4). Marked expression of hsp-70 mRNA was detected in the all regions (cingulate, parietal, somatosensory, insular, entorhinal, piriform cortices) of cerebral cortex and all regions of hippocampus, and the central medial thalamic nucleus of the rats that developed severe seizures (stage 4-5). In addition, marked HSP-70 immunoreactivity was detected in the pyramidal cell layers of CA1 and CA3 regions of hippocampus, all regions (cingulate, parietal, somatosensory, insular, piriform cortices) of cerebral cortex, and the striatum of rats that developed severe seizures (stage 4-5). Furthermore, a marked expression of cyclooxygenase-2 (COX-2) mRNA and brain-derived neurotrophic factor (BDNF) mRNA levels by kainic acid-induced behavioral seizures (stage 3-4 or stage 4-5) was detected in all hippocampal pyramidal cell layers, granule layers of dentate gyrus, piriform cortex, neocortex, and amygdala. The present study suggest that the behavioral changes (seizure intensity and body temperature) and neuropathological damage after systemic administration of kainic acid are inconsistent between animals, and that these behavioral changes (severity of kainic acid-induced limbic seizures) might be correlated with gene expression of hsp-70 mRNA, COX-2 mRNA, and BDNF mRNA in rat brain.

Increased expression of zif268 mRNA in rat retrosplenial cortex following administration of phencyclidine.

Phencyclidine (PCP) has been shown to cause neurotoxicity in rat retrosplenial cortex following a single administration, although the precise mechanism underlying PCP-induced neurotoxicity is unclear. Using in situ hybridization and immunohistochemistry, we studied the effects of PCP on expression of immediate early gene zif268 mRNA and zif268 protein in the rat brain. High constitutive levels of zif268 mRNA and zif268 immunoreactivity were observed in the brain of control rats. Administration of PCP (12.5, 25 or 50 mg/kg, i.p., 6 h) caused marked induction of zif268 mRNA in the rat retrosplenial cortex, in a dose-dependent manner. However, the basal levels of zif268 mRNA in the other regions of cerebral cortex were decreased by administration of PCP. Emulsion-autoradiographical study suggested that marked expression of zif268 mRNA was observed in the layers III and IV of retrosplenial cortex where the neurotoxicity of PCP was detected. Furthermore, zif268 immunoreactivity in the layer IV of retrosplenial cortex was not changed by administration of PCP (25 mg/kg, i.p., 5 h), but that in the other layers of retrosplenial cortex was reduced by PCP. These results suggest that immediate early gene zif268 may, in part, play a role in the neurotoxicity of NMDA receptor antagonists such as PCP.

Uncompetitive inhibition of [3H]1,3-di-o-tolyl-guanidine-defined sigma binding sites by desipramine, propranolol and alprenolol in rat brain.

Desipramine, imipramine, clomipramine, (-)-propranolol, (-)-alprenolol, (+/-)-pentazocine and risperidone caused a concentration-dependent inhibition of 6 nM [3H]DTG (1,3-di-o-tolylguanidine)-defined sigma (sigma) binding with Ki values of about 0.5-2.5 microM in well-washed homogenates obtained from rat cerebral cortex. The saturation studies revealed that the inhibition by desipramine (1-4 microM), (-)-propranolol (1 microM) and (-)-alprenolol (3 microM) resulted from a reduction of the Bmax value without alteration of the Kd of [3H]DTG binding to the cortex or hippocampus. In contrast, imipramine, (+/-)-pentazocine, clomipramine and risperidone competitively attenuated the cortical or hippocampal [3H]DTG binding. These findings demonstrate the uncompetitive inhibition of [3H]DTG binding by neuroactive drugs, thereby providing further support for the possible multiple regulation of cerebral sigma receptors.

p-chlorophenylalanine-reversible reduction of sigma binding sites by chronic imipramine treatment in rat brain.

Repeated treatment with imipramine (10 mg/kg intraperitoneally (i.p.), once daily for 14 days) caused a decrease in the Bmax, without affecting the Kd, of [3H]DTG (1,3-di-o-tolylguanidine) binding to the haloperidol-sensitive sigma sites in the striatum, hippocampus and cerebral cortex of the rat. A similar reduction was observed after chronic administration of a selective serotonin uptake inhibitor, fluoxetine (10 mg/kg i.p., twice daily for 14 days), but not of a selective norepinephrine uptake inhibitor, desipramine (10 mg/kg i.p., once daily for 14 days). Neither a single injection of imipramine (10 mg/kg i.p.) nor addition of imipramine or fluoxetine into the binding assay medium mimicked the changes in the maximal binding of brain sigma sites induced by chronic treatment with these drugs. Finally, depletion of brain serotonin by means of repeated administration of p-chlorophenylalanine, which produces inhibition of the amine synthesis, blocked the ability of repeated imipramine treatment to reduce the maximal number of [3H]DTG binding sites in the striatum and hippocampus. The present results suggest that cerebral serotonergic transmission may play a role in the regulation of cerebral sigma binding sites in the rat.

3,4-methylenedioxymethamphetamine (MDMA, ecstasy)-induced egr-1 mRNA in rat brain: pharmacological manipulation.

Using in situ hybridization and immunohistochemical techniques, we examined the expression pattern of egr-1 mRNA and Egr-1 protein in several brain regions following administration of 3, 4-methylenedioxymethamphetamine (MDMA). Furthermore, we also studied the role of N-methyl-D-aspartate (NMDA) receptor, dopamine D(1) receptor, 5-hydroxytryptamine (5-HT) transporter or 5-HT(2A) receptor in the induction of egr-1 mRNA by MDMA. Basal constitutive levels of egr-1 mRNA were detected in control rat brains. A single administration of MDMA (10 mg/kg) caused marked induction of egr-1 mRNA in the prefrontal cortex, striatum and hippocampal dentate gyrus. However, no changes in the egr-1 mRNA levels were detected in the CA1 region of hippocampus and occipital cortex after administration of MDMA (10 mg/kg). Furthermore, the expression of egr-1 mRNA in the prefrontal cortex, striatum and hippocampal dentate gyrus after administration of MDMA (10 mg/kg) was blocked significantly by pretreatment with NMDA receptor antagonist (5R, 10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,b]-cyclohepten-5, 10-imine ((+)-MK801; 1 mg/kg), dopamine D(1) receptor antagonist SCH 23390 (1 mg/kg) or 5-HT uptake inhibitor paroxetine (5 mg/kg), but not by 5-HT(2A) receptor antagonist SR46349B (5 mg/kg). However, high basal levels of Egr-1 immunoreactivity in the rat brain were not altered by administration of MDMA (10 mg/kg). These results suggest that MDMA alters the expression of egr-1 mRNA in several regions of rat brain, and that the expression of egr-1 mRNA by MDMA in the prefrontal cortex, striatum and hippocampal dentate gyrus appears to be mediated, at least in part, by NMDA receptor, dopamine D(1) receptor and 5-HT transporter.

Differential effects of repeated dl-pentazocine treatment on sigma binding sites in discrete brain areas of the rat.

Repeated treatment with dl-pentazocine (5-10 mg/kg i.p.), but not d-methamphetamine (4.8 mg/kg i.p.), twice daily for 8 days diminished the specific [3H]1,3-di-o-tolylguanidine (DTG) binding to the haloperidol-sensitive sigma sites in rat striatum and hippocampus. Either drug failed to cause any changes in the binding to the hypothalamus and prefrontal cortex. The pentazocine-induced diminution in the striatum was accompanied by a decrease in the density with an increase in the affinity of the [3H]DTG binding. These data suggest that repetitive use of dl-pentazocine may influence the regulation systems of the sigma site in specific brain regions.

Temporal change of hippocampal enkephalin and dynorphin mRNA following trimethyltin intoxication in rats: effect of anticonvulsant.

Trimethyltin (TMT), an organic metal, has been known to induce behavioral abnormalities including seizures and aggression. We administered TMT to rats, then, behavioral changes as well as the changes of dynorphin and Met-enkephalin mRNA were observed with or without phenobarbital treatment in order to reveal the role of neuropeptides in seizure-generating mechanisms. Met-enkephalin mRNA was significantly increased at the 2nd to 6th day after TMT administration when seizure was frequently observed. Meanwhile, dynorphin mRNA was decreased significantly from the 2nd day to 16th day during aggression score remained high. Phenobarbital abolished not only seizures and aggression, but also the changes of neuropeptide expressions. These results suggest that the changes of dynorphin mRNA are more strongly associated with aggression than seizures, while Met-enkephalin changes correlate more with seizures.

Compensatory function of central dopaminergic system for suppressing psychic seizures--repeated plasma homovanillic acid measurement in refractory temporal lobe epilepsy.

Repeatedly measured plasma homovanillic acid concentration, as a clinically available index of central dopaminergic activity in a patient with temporal lobe epilepsy during a drug-free period, was significantly correlated with seizure frequency in the week immediately following, but not preceding, blood sampling days. This result suggests a compensatory function of the dopaminergic system in suppressing refractory psychic seizures.

[Chemosensitivity of cultured meningiomas].

Meningioma is one of the popular benign brain tumors. However, the recurrence of this tumor is not infrequently encountered. In an attempt to establish the useful adjuvant therapy for the recurrent meningioma, in vitro chemosensitivity study for meningioma was conducted. Among various chemotherapeutic agents tested here, cisplatin showed highest cytotoxicity on cultured meningioma cells. In conclusion, cisplatin may be useful in adjuvant chemotherapy for the recurrent meningioma.

Immunohistochemical observation of foci of muscle actin-positive tumor cells in meningiomas.

OBJECTIVE: It has been suggested that muscle actin is expressed in some meningiomas. The purpose of this study was to examine this hypothesis in a large number of meningiomas and to examine possible explanations for this expression. DESIGN: Sixty-five meningiomas were examined using immunohistochemistry for muscle actin. Meningiomas with foci of muscle actin-positive cells (n = 6) were further examined using monoclonal antibodies for desmin, epithelial membrane antigen, cytokeratin, and von Willebrand factor. These specimens were also stained for reticulin. SETTING: All tissues were obtained from surgical biopsy specimens at a large academic medical center. MAIN OUTCOME MEASURES: Meningioma cells were considered to express muscle actin if the expression was shown to localize specifically in meningothelial cells and whorls that were also positive for epithelial membrane antigen. RESULTS: Seventeen of 65 meningiomas were shown to contain muscle actin-positive cells. Scattered cells were positive in 11 cases, and in the remaining six cases we observed foci of muscle actin-positive cells, which had a propensity to form cellular whorls. These foci expressed epithelial membrane antigen, but stains for desmin, cytokeratin, von Willebrand factor, and reticulin were negative. CONCLUSIONS: Our findings suggest that meningioma cells elaborate muscle actin without showing differentiation into specific cell types.