[Research advances in contact lens-associated dry eye]

Dry eye is the most common disease in ophthalmic clinics besides refractive error, which seriously affects the life quality of patients and has become an important public health problem in China. Dry eye as a kind of multifactorial disease can be induced or accelerated by contact lens wear, which is considered as one of the risk factors of dry eye. Studies have shown that the incidence of dry eye is higher in contact lens wearers than in normal people. In 2017, the Tear Film and Ocular Surface Society included contact lens-associated dry eye (CLADE) in the iatrogenic dry eye for the first time, and its importance is evident. However, ophthalmologists mostly used to focus on serious complications such as keratitis caused by contact lens wear, and CLADE has not been well valued and understood. This article reviews the latest studies on the epidemiology, pathogenesis, diagnosis, prevention, and treatment of CLADE.

Cell-type specific modulation of NMDA receptors triggers antidepressant actions

Both the NMDA receptor (NMDAR) positive allosteric modulator (PAM), and antagonist, can exert rapid antidepressant effects as shown in several animal and human studies. However, how this bidirectional modulation of NMDARs causes similar antidepressant effects remains unknown. Notably, the initial cellular trigger, specific cell-type(s), and subunit(s) of NMDARs mediating the antidepressant-like effects of a PAM or an antagonist have not been identified. Here, we used electrophysiology, microdialysis, and NMR spectroscopy to evaluate the effect of a NMDAR PAM (rapastinel) or NMDAR antagonist, ketamine on NMDAR function and disinhibition-mediated glutamate release. Further, we used cell-type specific knockdown (KD), pharmacological, and behavioral approaches to dissect the cell-type specific role of GluN2B, GluN2A, and dopamine receptor subunits in the actions of NMDAR PAM vs. antagonists. We demonstrate that rapastinel directly enhances NMDAR activity on principal glutamatergic neurons in medial prefrontal cortex (mPFC) without any effect on glutamate efflux, while ketamine blocks NMDAR on GABA interneurons to cause glutamate efflux and indirect activation of excitatory synapses. Behavioral studies using cell-type-specific KD in mPFC demonstrate that NMDAR-GluN2B KD on Camk2a- but not Gad1-expressing neurons blocks the antidepressant effects of rapastinel. In contrast, GluN2B KD on Gad1- but not Camk2a-expressing neurons blocks the actions of ketamine. The results also demonstrate that Drd1-expressing pyramidal neurons in mPFC mediate the rapid antidepressant actions of ketamine and rapastinel. Together, these results demonstrate unique initial cellular triggers as well as converging effects on Drd1-pyramidal cell signaling that underlie the antidepressant actions of NMDAR-positive modulation vs. NMDAR blockade.

Antibodies From Children With PANDAS Bind Specifically to Striatal Cholinergic Interneurons and Alter Their Activity

OBJECTIVE

Pediatric obsessive-compulsive disorder (OCD) sometimes appears rapidly, even overnight, often after an infection. Pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections, or PANDAS, describes such a situation after infection with Streptococcus pyogenes. PANDAS may result from induced autoimmunity against brain antigens, although this remains unproven. Pilot work suggests that IgG antibodies from children with PANDAS bind to cholinergic interneurons (CINs) in the striatum. CIN deficiency has been independently associated with tics in humans and with repetitive behavioral pathology in mice, making it a plausible locus of pathology. The authors sought to replicate and extend earlier work and to investigate the cellular effects of PANDAS antibodies on cholinergic interneurons.

METHODS

Binding of IgG to specific neurons in human and mouse brain slices was evaluated ex vivo after incubation with serum from 27 children with rigorously characterized PANDAS, both at baseline and after intravenous immunoglobulin (IVIG) treatment, and 23 matched control subjects. Binding was correlated with symptom measures. Neural activity after serum incubation was assessed in mouse slices using molecular markers and electrophysiological recording.

RESULTS

IgG from children with PANDAS bound to CINs, but not to several other neuron types, more than IgG from control subjects, in three independent cohorts of patients. Post-IVIG serum had reduced IgG binding to CINs, and this reduction correlated with symptom improvement. Baseline PANDAS sera decreased activity of striatal CINs, but not of parvalbumin-expressing GABAergic interneurons, and altered their electrophysiological responses, in acute mouse brain slices. Post-IVIG PANDAS sera and IgG-depleted baseline sera did not alter the activity of striatal CINs.

CONCLUSIONS

These findings provide strong evidence for striatal CINs as a critical cellular target that may contribute to pathophysiology in children with rapid-onset OCD symptoms, and perhaps in other conditions.

Luteoloside Ameliorates Palmitic Acid-Induced in Vitro Model of Non-alcoholic Fatty Liver Disease via Activating STAT3-Triggered Hepatocyte Regeneration

Luteoloside (Lute), a bioactive natural ingredient, widely exists in nature and possesses hepatoprotective and hepatocyte proliferation-promoting properties. This study aimed to investigate whether Lute could counteract non-alcoholic fatty liver disease (NAFLD)-caused hepatocyte damage via its stimulation of hepatocyte regeneration efficacy and to explore the involved mechanism. LO2 cells and primary hepatocytes were used to examine the hepatocyte proliferation effects of Lute under physiological conditions and in the palmitic acid (PA)- induced in vitro model of NAFLD. STAT3 and cell cycle-related proteins (cyclin D1, c-myc and p21) were evaluated by Western blot. Under physiological conditions, LO2 cells and primary hepatocytes treated with various concentration of Lute for 12 and 24 h showed increased hepatocyte proliferation, especially with 20 μM treatment for 24 h. More notably, under the model conditions, co-incubation with 20 μM of Lute also markedly reversed PA-induced inhibition of cell proliferation and viability in primary hepatocytes. Mechanistically, Lute could activate STAT3 and subsequently increase cyclin D1 and cmyc expression, which positively regulates cell cycle progression, and decrease expression of p21, an inhibitor of cell cycle progression. Furthermore, Luteinduced hepatocyte proliferation-promoting efficacy was abolished by STAT3 inhibitor stattic. Collectively, Lute can alleviate PA-induced hepatocyte damage via activating STAT3-mediated hepatocyte regeneration.

GABA interneurons are the cellular trigger for ketamine's rapid antidepressant actions

A single subanesthetic dose of ketamine, an NMDA receptor (NMDAR) antagonist, produces rapid and sustained antidepressant actions in depressed patients, addressing a major unmet need for the treatment of mood disorders. Ketamine produces a rapid increase in extracellular glutamate and synaptic formation in the prefrontal cortex, but the initial cellular trigger that initiates this increase and ketamine's behavioral actions has not been identified. To address this question, we used a combination of viral shRNA and conditional mutation to produce cell-specific knockdown or deletion of a key NMDAR subunit, GluN2B, implicated in the actions of ketamine. The results demonstrated that the antidepressant actions of ketamine were blocked by GluN2B-NMDAR knockdown on GABA (Gad1) interneurons, as well as subtypes expressing somatostatin (Sst) or parvalbumin (Pvalb), but not glutamate principle neurons in the medial prefrontal cortex (mPFC). Further analysis of GABA subtypes showed that cell-specific knockdown or deletion of GluN2B in Sst interneurons blocked or occluded the antidepressant actions of ketamine and revealed sex-specific differences that are associated with excitatory postsynaptic currents on mPFC principle neurons. These findings demonstrate that GluN2B-NMDARs on GABA interneurons are the initial cellular trigger for the rapid antidepressant actions of ketamine and show sex-specific adaptive mechanisms to GluN2B modulation.

Medial PFC AMPA receptor and BDNF signaling are required for the rapid and sustained antidepressant-like effects of 5-HT1A receptor stimulation

We previously reported that the serotonergic system is important for the antidepressant-like effects of ketamine, a non-competitive N-methyl-D-aspartate receptor antagonist, which produces rapid and long-lasting antidepressant effects in patients with major depressive disorder (MDD). In particular, selective stimulation of the 5-HT_1A receptor in the medial prefrontal cortex (mPFC), as opposed to the somatic 5-HT_1A autoreceptor, has been shown to play a critical role in the antidepressant-like actions of ketamine. However, the detailed mechanisms underlying mPFC 5-HT_1A receptor-mediated antidepressant-like effects are not fully understood. Here we examined the involvement of the glutamate AMPA receptor and brain-derived neurotrophic factor (BDNF) in the antidepressant-like effects of 5-HT_1A receptor activation in the mPFC. The results show that intra-mPFC infusion of the 5-HT_1A receptor agonist 8-OH-DPAT induces rapid and long-lasting antidepressant-like effects in the forced swim, novelty-suppressed feeding, female urine sniffing, and chronic unpredictable stress tests. In addition, the results demonstrate that the antidepressant-like effects of intra-mPFC infusion of 8-OH-DPAT are blocked by co-infusion of an AMPA receptor antagonist or an anti-BDNF neutralizing antibody. In addition, mPFC infusion of 8-OH-DPAT increased the phosphorylation of signaling proteins downstream of BDNF, including mTOR, ERK, 4EBP1, and p70S6K. Finally, selective stimulation of the 5-HT_1A receptor increased levels of synaptic proteins and synaptic function in the mPFC. Collectively, these results indicate that selective stimulation of 5-HT_1A receptor in the mPFC exerts rapid and sustained antidepressant-like effects via activation of AMPA receptor/BDNF/mTOR signaling in mice, which subsequently increase synaptic function in the mPFC, and provide evidence for the 5-HT_1A receptor as a target for the treatment of MDD.

[Effect of fragmented sleep on postoperative cognitive function and central neuroinflammation]

Objective: To investigate the effect of sleep fragmentation on perioperative neurocognitive disorders (PND) and central neuroinflammation by simulating sleep patterns of postoperative patients with sleep fragmentation in aged mice. Methods: Thirty-two elderly ICR mice were randomly divided into four groups (n=8): normal group (C), surgery group (S), fragmented sleep group (F), and surgery+fragmented sleep group (D). Fragmented sleep was conducted after internal fixation of tibia fractures, cognitive function was evaluated by novel object recognition (NOR) and fear conditioning (FC) test, and changes in expression of inflammatory cytokines in hippocampus were detected by ELISA. Results: NOR test: the recognition index (RI) of mice in group C, group S, group F and group D was 0.69±0.07, 0.48±0.07, 0.54±0.10 and 0.50±0.12, respectively. The RI of mice in group S, group F and group D was significantly lower than that in group C (t=4.885, 3.521 and 4.433, all P<0.01). There was no significant difference in RI between group S and group D (t=0.967 1, P>0.05). Contextual FC test: the freezing time of mice in group C, group S, group F and group D was(21.34±6.48), (13.83±4.26), (11.50±6.25) and (6.17±4.77) s, respectively. The freezing time of mice in group S, group F and group D was significantly lower than that in group C (t=2.722, 3.566, 5.496, P<0.05 or P<0.01). The freezing time of mice in group D was significantly lower than that in group S (t=2.774, P<0.05). Cue FC test: the freezing time of mice in group C, group S, group F and group D was (74.36±17.09), (43.91±9.71), (46.34±13.43) and (24.90±14.21) s, respectively. The freezing time of mice in group S, group F and group D was significantly lower than that in group C (t=4.393, 4.043 and 7.136, all P<0.01). The freezing time of mice in group D was significantly lower than that in group S (t=2.743, P<0.05). The levels of TNF-α, IL-6 and IL-1β in hippocampus of mice in group S, F and D were significantly higher than those in group C, while the levels of TNF-α and IL-6 in hippocampus of mice in group D were significantly higher than those in group S, with statistically significant differences (P<0.05 or P<0.01). Conclusion: Postoperative fragmented sleep aggravates postoperative cognitive impairment and increases the hippocampal neuroinflammation in aged mice.

[The rotational stability of Toric intraocular lenses and influencing factors in cataract patients with different axial length]

Objective: To evaluate the rotational stability of the Toric intraocular lens (TIOL) and influencing factors in cataract patients with different axial length. Methods: This retrospective cohort study consecutively enrolled patients who had phacoemulsification and AcrySof TIOL implantation in Peking University Third Hospital from May 2018 to January 2019. Based on axial length, patients were divided into two groups. Group A consisted of patients whose axial length was ≤ 24 mm. Patients whose axial length was >24 mm were included in group B. Data at three months postoperatively were used to evaluate the rotational stability of TIOL and its correlation with axial length, corneal white to white distance, lens thickness and TIOL spherical power. And t test, nonparametric test, chi-square test and Spearman test were used for statistical analysis. Results: Group A enrolled 39 patients (17 males and 22 females), with a median age of 74 years (range, 36-86 years). Group B enrolled 26 patients (11 males and 15 females), with a median age of 68 years (range, 36-86 years). For the efficacy of TIOL, in group A, the best corrected distance visual acuity (BCDVA, logarithm of the minimum angle of resolution) was 0.30 (0.10, 1.00) preoperatively and 0.10 (0.00, 0.60) postoperatively, and the astigmatism was 2.11 (0.95, 5.10) D preoperatively and 1.00 (0.00, 1.75) D postoperatively. In group B, the BCDVA was 0.36 (0.05, 1.00) preoperatively and 0.05 (0.00, 0.40) postoperatively, and the astigmatism was 2.00 (0.78, 3.76) D preoperatively and 0.75 (0.00, 2.25) D postoperatively. Between group A and group B, there were no significant differences in BCDVA (P=0.604) and astigmatism (P=0.789) preoperatively.In these two groups, postoperative BCDVA and astigmatism both significantly improved compared to preoperative parameters (both P<0.01). Between group A and group B, there were no significant differences in BCDVA (P=0.536) and astigmatism (P=0.076) postoperatively. In terms of rotational stability, the rotation in group A was 5.15°±3.62°, and that in group B was 6.50°±4.66°. There was no statistical difference between two groups (P=0.195). As for predictability, the percentage of eyes with rotation ≤5° was 59.0% (23 eyes) in group A and 50.0% (13 eyes) in group B. There was no statistical difference between the two groups (P=0.647). There was no significant correlation between the rotational stability of TIOL and axial length, corneal white to white distance, lens thickness or TIOL spherical power (P=0.836, 0.568, 0.170, 0.365). Conclusions: The rotational stability of TIOL at three months postoperatively in patients whose axial length >24 mm is of no difference with patients whose axial length ≤ 24 mm. It has no correlation with axial length, corneal white to white distance, lens thickness and TIOL spherical power. (Chin J Ophthalmol, 2020, 56: 41-46).

N-Methyl-D-aspartate receptor antagonist d-methadone produces rapid, mTORC1-dependent antidepressant effects

Currently available antidepressants have a delayed onset and limited efficacy, highlighting the need for new, rapid and more efficacious agents. Ketamine, an NMDA receptor antagonist, has emerged as a new rapid-acting antidepressant, effective even in treatment resistant patients. However, ketamine induces undesired psychotomimetic and dissociative side effects that limit its clinical use. The d-stereoisomer of methadone (dextromethadone; REL-1017) is a noncompetitive NMDA receptor antagonist with an apparently favorable safety and tolerability profile. The current study examined the rapid and sustained antidepressant actions of d-methadone in several behavioral paradigms, as well as on mTORC1 signaling and synaptic changes in the medial prefrontal cortex (mPFC). A single dose of d-methadone promoted rapid and sustained antidepressant responses in the novelty-suppressed feeding test (NSFT), a measure of anxiety, and in the female urine sniffing test (FUST), a measure of motivation and reward. D-methadone also produced a rapid reversal of the sucrose preference deficit, a measure of anhedonia, in rats exposed to chronic unpredictable stress. D-methadone increased phospho-p70S6 kinase, a downstream target of mTORC1 in the mPFC, and intra-mPFC infusion of the selective mTORC1 inhibitor rapamycin blocked the antidepressant actions of d-methadone in the FUST and NSFT. D-methadone administration also increased levels of the synaptic proteins, PSD95, GluA1, and Synapsin 1 and enhanced synaptic function in the mPFC. Studies in primary cortical cultures show that d-methadone also increases BDNF release, as well as phospho-p70S6 kinase. These findings indicate that d-methadone induces rapid antidepressant actions through mTORC1-mediated synaptic plasticity in the mPFC similar to ketamine.

Ketamine rapidly reverses stress-induced impairments in GABAergic transmission in the prefrontal cortex in male rodents

Dysfunction of medial prefrontal cortex (mPFC) in association with imbalance of inhibitory and excitatory neurotransmission has been implicated in depression. However, the precise cellular mechanisms underlying this imbalance, particularly for GABAergic transmission in the mPFC, and the link with the rapid acting antidepressant ketamine remains poorly understood. Here we determined the influence of chronic unpredictable stress (CUS), an ethologically validated model of depression, on synaptic markers of GABA neurotransmission, and the influence of a single dose of ketamine on CUS-induced synaptic deficits in mPFC of male rodents. The results demonstrate that CUS decreases GABAergic proteins and the frequency of inhibitory post synaptic currents (IPSCs) of layer V mPFC pyramidal neurons, concomitant with depression-like behaviors. In contrast, a single dose of ketamine can reverse CUS-induced deficits of GABA markers, in conjunction with reversal of CUS-induced depressive-like behaviors. These findings provide further evidence of impairments of GABAergic synapses as key determinants of depressive behavior and highlight ketamine-induced synaptic responses that restore GABA inhibitory, as well as glutamate neurotransmission.

Comparative Analysis of Visual System Disability Evaluation Criteria between China and the United States

Gradation of Disability in Human Body Injuries （hereinafter referred to as Gradation） has been released and used since January 2017, and has become the most widely used standard in forensic science practice. This paper calculates and rates the visual system evaluation provisions of the current domestic disability evaluation criteria represented by the Gradation which used the methods of Guides to the Evaluation of Permanent Impairment （hereinafter referred to as GEPI） issued by American Medical Association （AMA）. Through comparing, a good correlation between the provisions in Gradation and whole person impairment rating index in GEPI was shown. On the basis of this, suggestions are put forward to amend some provisions of Gradation, in order to provide reference for the revision and further improvement of domestic standards and provisions.

Application of PRVEP Waveform Amplitude Ratio to Evaluate Visual Acuity and Its Forensic Significance

Abstract

Objective To research the correlation between the visual acuity ratio and pattern reversal visual evoked potential （PRVEP） P100 waveform amplitude ratio of both eyes. Methods Forty-seven volunteers were selected, and the visual chart visual acuity of both eyes was measured. The visual acuity ratio of the eye with poor vision to the eye with better vision was calculated by five grade notation method. The amplitudes of P100 waveforms of both eyes were recorded respectively by using black-and-white checkerboard PRVEP and chosing 1°, 15' stimulating visual angle, and the ratio of amplitudes between the two eyes was also calculated. SPSS 20.0 software was used to analyze the correlation between the visual acuity ratio and the ratio of P100 waveform amplitudes between the two eyes. Return test and linear regression analysis with the binocular ratio of P100 waveform amplitudes as the independent variable （x） and the binocular visual acuity ratio as the dependent variable （y） were made. Results There was a positive correlation between the binocular visual acuity ratio and the ratio of P100 waveform amplitudes under 15' stimulating visual angle （Pearson correlation coefficient was 0.62, P=0.000）. The fitting linear regression equation was y=0.090 x+0.846 （F=20.954, P=0.000）. There was no significant correlation between the binocular ratio of visual acuity and the binocular ratio of P100 waveform amplitudes under 1° stimulating visual angle （P>0.05）. Results of return test showed that there was no statistical significance in the difference between visual acuity estimated by equation and actual detected visual acuity. Conclusion In forensic appraisal of monocular injury, fitting linear regression equation of binocular visual acuity ratio and the binocular ratio of P100 waveform amplitudes under 15' stimulating visual angle, is helpful for visual acuity level estimation of the injured eye to some extent.

Sestrin modulator NV-5138 produces rapid antidepressant effects via direct mTORC1 activation

Preclinical studies demonstrate that rapid acting antidepressants, including ketamine require stimulation of mTORC1 signaling. This pathway is regulated by neuronal activity, endocrine and metabolic signals, notably the amino acid leucine, which activates mTORC1 signaling via binding to the upstream regulator sestrin. Here, we examined the antidepressant actions of NV-5138, a novel highly selective small molecule modulator of sestrin that penetrates the blood brain barrier. The results demonstrate that a single dose of NV-5138 produced rapid and long-lasting antidepressant effects, and rapidly reversed anhedonia caused by chronic stress exposure. The antidepressant actions of NV-5138 required BDNF release as the behavioral responses are blocked by infusion of a BDNF neutralizing antibody into the medial prefrontal cortex (mPFC) or in mice with a knock-in of a BDNF polymorphism that blocks activity dependent BDNF release. NV-5138 administration also rapidly increased synapse number and function in the mPFC, and reversed the synaptic deficits caused by chronic stress. Together, the results demonstrate that NV-5138 produced rapid synaptic and antidepressant behavioral responses via activation of the mTORC1 pathway and BDNF signaling, indicating that pharmacological modulation of sestrin is a novel approach for development of rapid acting antidepressants.

[Comparative analysis of anatomic and non-anatomic hepatectomy for single small hepatocellular carcinoma with microvascular invasion]

Objective: To compare the efficacy and safety of anatomic hepatectomy and non-anatomic hepatectomy in the treatment of single small Hepatocellular carcinoma with MVI. Methods: The clinical data of 84 patients with single small Hepatocellular carcinoma with MVI in Beijing Chaoyang Hospital between January 2008 and December 2013 were retrospectively analyzed. Patients undergoing anatomical hepatectomy were enrolled in the AR group, and the patients undergoing non-anatomic hepatectomy were enrolled in the NR group. The efficacy and survival rate of the two groups were compared. Results: (1) Operation time, numbers of patients with volume of intraoperative blood loss ≥300 ml and number of patients with blood transfusion were (170±41)minutes, 8, 7 in the AR group and (148±35)minutes, 19, 18 in the NR group, respectively, with statistically significant differences between the 2 groups (P<0.05). (2) The 1-year, 2-year and 3-year overall survival rate were 85.7%, 68.6%, 57.1% in the AR group and 79.6%, 53.1%, 42.9% in the NR group, respectively. The 1-year, 2-year and 3-year progression-free survival rate were 80.0%, 62.9%, 51.4% in the AR group and 71.4%, 49.0%, 38.8%, in the NR group, respectively. There were statistically significant differences between the 2 groups both in the overall survival rate and the progression-free survival rate (P<0.05). (3) Prognostic factors analysis of HCC patients with MVI: result of univariate analysis showed that maximum diameter of tumor and surgical procedures were relative factors affecting overall survival and progression-free survival of HCC patients with MVI, AFP level was relative factors affecting progression-free survival of HCC patients with MVI, with statistically significant differences (P<0.05). Result of multivariate analysis showed that maximum diameter of tumor between 3.0 and 5.0 cm and non-anatomic liver resection were independent factors affecting poor overall survival and progression-free survival of HCC patients with MVI, and AFP≥20 μg/L and total bilirubin ≥20 μmol/L were independent factors affecting poor progression-free survival of HCC patients with MVI, with a statistically significant differences (P< 0.05). Conclusion: Anatomic hepatectomy for patients with single small hepatocellular carcinoma with microvascular invasion has better clinical efficacy and safety.

[Contrast Visual Evoked Potentials under Pattern Stimulus in Ocular Trauma]

OBJECTIVES

To study the characteristic of contrast visual evoked potentials （CVEP） in patients with ocular trauma.

METHODS

Sixty patients defined as ocular trauma by forensic clinical examination in our center were selected, and split into 0.2-0.3 （Group A）, 0.3-0.5 （Group B） and ≥0.5 （Group C） according to the best corrected visual acuity. The variation characteristics of wave amplitude and latency of CVEP under 100%, 25% and 10% contrast were observed and analyzed statistically.

RESULTS

（1） Under the same contrast, the wave amplitude of P₁₀₀ decreased with the decrease of stimulus perspective. （2） Under the same stimulus perspective, the wave amplitude of P₁₀₀ decreased with the decrease of contrast （P<0.05）. （3） Under the contrast of 100% and 25% with the same stimulus perspective （except 100% 7' perspective stimulus）, the difference between group A and group B had no statistical significance （P>0.05）. Between group A and group C, group B and group C, the wave amplitude of P₁₀₀ gradually increased with the increase of vision （P<0.05）. Under the contrast of 10% with 15' stimulus perspective, the wave amplitude of P₁₀₀ increased with the increase of vision （P<0.05）. （4） Under the same contrast with the same stimulation perspective, the latency of P₁₀₀ wave shortened with the increase of vision, while the difference had no statistical significance （P>0.05）. Under the same stimulus perspective, the latency of P₁₀₀ wave was prolonged with the decrease of contrast （P>0.05）.

CONCLUSIONS

CVEP may become one of the possible methods for the evaluation of contrast visual acuity.

Ketamine Strengthens CRF-Activated Amygdala Inputs to Basal Dendrites in mPFC Layer V Pyramidal Cells in the Prelimbic but not Infralimbic Subregion, A Key Suppressor of Stress Responses

A single sub-anesthetic dose of ketamine, a short-acting NMDA receptor blocker, induces a rapid and prolonged antidepressant effect in treatment-resistant major depression. In animal models, ketamine (24 h) reverses depression-like behaviors and associated deficits in excitatory postsynaptic currents (EPSCs) generated in apical dendritic spines of layer V pyramidal cells of medial prefrontal cortex (mPFC). However, little is known about the effects of ketamine on basal dendrites. The basal dendrites of layer V cells receive an excitatory input from pyramidal cells of the basolateral amygdala (BLA), neurons that are activated by the stress hormone CRF. Here we found that CRF induces EPSCs in PFC layer V cells and that ketamine enhanced this effect through the mammalian target of rapamycin complex 1 synaptogenic pathway; the CRF-induced EPSCs required an intact BLA input and were generated primarily in basal dendrites. In contrast to its detrimental effects on apical dendritic structure and function, chronic stress did not induce a loss of CRF-induced EPSCs in basal dendrites, thereby creating a relative imbalance in favor of amygdala inputs. The effects of ketamine were complex: ketamine enhanced apical EPSC responses in all mPFC subregions, anterior cingulate (AC), prelimbic (PL), and infralimbic (IL) but enhanced CRF-induced EPSCs only in AC and PL-responses were unchanged in IL, a critical area for suppression of stress responses. We propose that by restoring the strength of apical inputs relative to basal amygdala inputs, especially in IL, ketamine would ameliorate the hypothesized disproportional negative influence of the amygdala in chronic stress and major depression.

REDD1 is essential for stress-induced synaptic loss and depressive behavior

Major depressive disorder (MDD) affects up to 17% of the population, causing profound personal suffering and economic loss (1). Clinical and pre-clinical studies have revealed that prolonged stress and MDD are associated with neuronal atrophy of cortical and limbic brain regions (2-9), but the molecular mechanisms underlying these morphological alterations have not yet been identified. Here, we show that stress increases levels of REDD1 (regulated in development and DNA damage responses 1), an inhibitor of mTORC1 (mammalian/mechanistic target of rapamycin complex 1) (10), in rat prefrontal cortex (PFC). This is concurrent with a decrease in phosphorylation of signaling targets of mTORC1, which is implicated in protein synthesis-dependent synaptic plasticity. We also found that REDD1 levels are increased in the postmortem PFC of human subjects with MDD relative to matched controls. Mutant mice with a deletion of REDD1 are resilient to the behavioral, synaptic, and mTORC1 signaling deficits caused by chronic unpredictable stress (CUS), while viral-mediated over expression of REDD1 in the rat PFC is sufficient to cause anxiety- and depressive-like behaviors and neuronal atrophy. Taken together, these postmortem and pre-clinical findings identify REDD1 as a critical mediator underlying the atrophy of neurons and depressive behavior caused by chronic stress exposure.

Origin of shape resonance in second-harmonic generation from metallic nanohole arrays

Second-harmonic generation (SHG) from periodic arrays of subwavelength rectangular air hole with various aspect ratios perforated in gold thin films can get resonantly enhanced for some specific geometric shapes. Here we clarify the physical origin of this shape resonance effect. A nonlinear coupled-mode theory is set up to solve energy conversion from fundamental wave (FW) mode to second-harmonic wave (SHW) mode within the nanoscale air hole. It reveals that several physical mechanisms, including the FW mode excitation amplitude, FW-SHW modal spatial overlap, FW-SHW mode phase mismatch, and SHW mode attenuation, are all geometric shape sensitive and altogether act to induce the SHG shape resonance effect. The theory agrees well with experimental observations and provides an accurate and complete explanation for the long-emphasized but elusive shape effect. The study may stimulate deeper insights to visualize general nonlinear nanophotonic processes and pave the way to engineering high-efficiency nonlinear nanophotonic devices.

Medial prefrontal D1 dopamine neurons control food intake

Although the prefrontal cortex influences motivated behavior, its role in food intake remains unclear. Here, we demonstrate a role for D1-type dopamine receptor-expressing neurons in the medial prefrontal cortex (mPFC) in the regulation of feeding. Food intake increases activity in D1 neurons of the mPFC in mice, and optogenetic photostimulation of D1 neurons increases feeding. Conversely, inhibition of D1 neurons decreases intake. Stimulation-based mapping of prefrontal D1 neuron projections implicates the medial basolateral amygdala (mBLA) as a downstream target of these afferents. mBLA neurons activated by prefrontal D1 stimulation are CaMKII positive and closely juxtaposed to prefrontal D1 axon terminals. Finally, photostimulating these axons in the mBLA is sufficient to increase feeding, recapitulating the effects of mPFC D1 stimulation. These data describe a new circuit for top-down control of food intake.

Scopolamine rapidly increases mammalian target of rapamycin complex 1 signaling, synaptogenesis, and antidepressant behavioral responses

BACKGROUND

Clinical studies report that scopolamine, an acetylcholine muscarinic receptor antagonist, produces rapid antidepressant effects in depressed patients, but the mechanisms underlying the therapeutic response have not been determined. The present study examines the role of the mammalian target of rapamycin complex 1 (mTORC1) and synaptogenesis, which have been implicated in the rapid actions of N-methyl-D-aspartate receptor antagonists.

METHODS

The influence of scopolamine on mTORC1 signaling was determined by analysis of the phosphorylated and activated forms of mTORC1 signaling proteins in the prefrontal cortex (PFC). The numbers and function of spine synapses were analyzed by whole cell patch clamp recording and two-photon image analysis of PFC neurons. The actions of scopolamine were examined in the forced swim test in the absence or presence of selective mTORC1 and glutamate receptor inhibitors.

RESULTS

The results demonstrate that a single, low dose of scopolamine rapidly increases mTORC1 signaling and the number and function of spine synapses in layer V pyramidal neurons in the PFC. Scopolamine administration also produces an antidepressant response in the forced swim test that is blocked by pretreatment with the mTORC1 inhibitor or by a glutamate alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor antagonist.

CONCLUSIONS

Taken together, the results demonstrate that the antidepressant actions of scopolamine require mTORC1 signaling and are associated with increased glutamate transmission, and synaptogenesis, similar to N-methyl-D-aspartate receptor antagonists. These findings provide novel targets for safer and more efficacious rapid-acting antidepressant agents.

GSK-3 inhibition potentiates the synaptogenic and antidepressant-like effects of subthreshold doses of ketamine

A single dose of the short-acting NMDA antagonist ketamine produces rapid and prolonged antidepressant effects in treatment-resistant patients with major depressive disorder (MDD), which are thought to occur via restoration of synaptic connectivity. However, acute dissociative side effects and eventual fading of antidepressant effects limit widespread clinical use of ketamine. Recent studies in medial prefrontal cortex (mPFC) show that the synaptogenic and antidepressant-like effects of a single standard dose of ketamine in rodents are dependent upon activation of the mammalian target of rapamycin (mTOR) complex 1 (mTORC1) signaling pathway together with inhibitory phosphorylation of glycogen synthase kinase-3 (GSK-3), which relieves its inhibitory in influence on mTOR. Here, we found that the synaptogenic and antidepressant-like effects of a single otherwise subthreshold dose of ketamine were potentiated when given together with a single dose of lithium chloride (a nonselective GSK-3 inhibitor) or a preferential GSK-3β inhibitor; these effects included rapid activation of the mTORC1 signaling pathway, increased inhibitory phosphorylation of GSK-3β, increased synaptic spine density/diameter, increased excitatory postsynaptic currents in mPFC layer V pyramidal neurons, and antidepressant responses that persist for up to 1 week in the forced-swim test model of depression. The results demonstrate that low, subthreshold doses of ketamine combined with lithium or a selective GSK-3 inhibitor are equivalent to higher doses of ketamine, indicating the pivotal role of the GSK-3 pathway in modulating the synaptogenic and antidepressant responses to ketamine. The possible mitigation by GSK-3 inhibitors of the eventual fading of ketamine's antidepressant effects remains to be explored.

Zoledronate inhibits phosphate and bone morphogenetic protein 2-induced extracellular calcification of vascular smooth muscle cells in vitro

The aim of this study was to explore the effects of the bisphosphonate zoledronate on calcification induced by inorganic phosphate (Pi) and/or bone morphogenetic protein 2 (BMP-2) and the underlying mechanisms. Primary vascular smooth muscle cells (VSMCs) from rats were treated with 3 mM Pi or 3 mM Pi/BMP-2, with and without addition of zoledronate; 1.4 mM Pi served as a control. Calcium deposits, expression of core binding factor α-1 (Cbfa-1), osteopontin (OPN), parathyroid pituitary-specific transcription factor (Pit)-1 and Pit-2, and Pi uptake of VSMCs was determined. The calcification of VSMCs induced by elevated Pi or Pi/BMP-2 was significantly inhibited by zoledronate. The expression of Cbfa-1, OPN and Pit-1 was increased significantly after treatment with an elevated level of Pi or Pi/BMP-2, and this expression was significantly suppressed by addition of zoledronate. Pi uptake of VSMCs increased following treatment with elevated Pi and significantly decreased by addition of zoledronate. These results indicated that zoledronate effectively inhibited calcification induced by Pi/BMP-2, and this may have been achieved by means of the downregulation of expression of calcification-related proteins and uptake of Pi.

Brain-derived neurotrophic factor Val66Met allele impairs basal and ketamine-stimulated synaptogenesis in prefrontal cortex

BACKGROUND

Knock-in mice with the common human brain-derived neurotrophic factor (BDNF) Val66Met polymorphism have impaired trafficking of BDNF messenger RNA to dendrites. It was hypothesized, given evidence that local synapse formation is dependent on dendritic translation of BDNF messenger RNA, that loss-of-function Met allele mice would show synaptic deficits both at baseline and in response to ketamine, an N-methyl-D-aspartate antagonist that stimulates synaptogenesis in prefrontal cortex (PFC).

METHODS

Whole-cell recordings from layer V medial PFC pyramidal cells in brain slices were combined with two-photon laser scanning for analysis of wildtype, Val/Met, and Met/Met mice both at baseline and in response to a low dose of ketamine.

RESULTS

Val/Met and Met/Met mice were found to have constitutive atrophy of distal apical dendrites and decrements in apically targeted excitatory postsynaptic currents in layer V pyramidal cells of PFC. In addition, spine density and diameter were decreased, indicative of impaired synaptic formation/maturation (synaptogenesis). In Met/Met mice the synaptogenic effect of ketamine was markedly impaired, consistent with the idea that synaptogenesis is dependent on dendritic translation/release of BDNF. In parallel behavioral studies, we found that the antidepressant response to ketamine in the forced swim test was blocked in Met/Met mice.

CONCLUSIONS

The results demonstrate that expression of the BDNF Met allele in mice results in basal synaptic deficits and blocks synaptogenic and antidepressant actions of ketamine in PFC, suggesting that the therapeutic response to this drug might be attenuated or blocked in depressed patients who carry the loss of function Met allele.

Signaling pathways underlying the rapid antidepressant actions of ketamine

Currently available medications have significant limitations, most notably low response rate and time lag for treatment response. Recent clinical studies have demonstrated that ketamine, an NMDA receptor antagonist produces a rapid antidepressant response (within hours) and is effective in treatment resistant depressed patients. Molecular and cellular studies in rodent models demonstrate that ketamine rapidly increases synaptogenesis, including increased density and function of spine synapses, in the prefrontal cortex (PFC). Ketamine also produces rapid antidepressant actions in behavioral models of depression, and reverses the deficits in synapse number and behavior resulting from chronic stress exposure. These effects of ketamine are accompanied by stimulation of the mammalian target of rapamycin (mTOR), and increased levels of synaptic proteins. Together these studies indicate that ketamine rapidly reverses the atrophy of spines in the PFC and thereby causes a functional reconnection of neurons that underlies the rapid behavioral responses. These findings identify new targets for rapid acting antidepressants that are safer than ketamine. This article is part of a Special Issue entitled 'Anxiety and Depression'.

Glutamate N-methyl-D-aspartate receptor antagonists rapidly reverse behavioral and synaptic deficits caused by chronic stress exposure

BACKGROUND

Despite widely reported clinical and preclinical studies of rapid antidepressant actions of glutamate N-methyl-D-aspartate (NMDA) receptor antagonists, there has been very little work examining the effects of these drugs in stress models of depression that require chronic administration of antidepressants or the molecular mechanisms that could account for the rapid responses.

METHODS

We used a rat 21-day chronic unpredictable stress (CUS) model to test the rapid actions of NMDA receptor antagonists on depressant-like behavior, neurochemistry, and spine density and synaptic function of prefrontal cortex neurons.

RESULTS

The results demonstrate that acute treatment with the noncompetitive NMDA channel blocker ketamine or the selective NMDA receptor 2B antagonist Ro 25-6981 rapidly ameliorates CUS-induced anhedonic and anxiogenic behaviors. We also found that CUS exposure decreases the expression levels of synaptic proteins and spine number and the frequency/amplitude of synaptic currents (excitatory postsynaptic currents) in layer V pyramidal neurons in the prefrontal cortex and that these deficits are rapidly reversed by ketamine. Blockade of the mammalian target of rapamycin protein synthesis cascade abolishes both the behavioral and biochemical effects of ketamine.

CONCLUSIONS

The results indicate that the structural and functional deficits resulting from long-term stress exposure, which could contribute to the pathophysiology of depression, are rapidly reversed by NMDA receptor antagonists in a mammalian target of rapamycin dependent manner.

mTOR-dependent synapse formation underlies the rapid antidepressant effects of NMDA antagonists

The rapid antidepressant response after ketamine administration in treatment-resistant depressed patients suggests a possible new approach for treating mood disorders compared to the weeks or months required for standard medications. However, the mechanisms underlying this action of ketamine [a glutamate N-methyl-D-aspartic acid (NMDA) receptor antagonist] have not been identified. We observed that ketamine rapidly activated the mammalian target of rapamycin (mTOR) pathway, leading to increased synaptic signaling proteins and increased number and function of new spine synapses in the prefrontal cortex of rats. Moreover, blockade of mTOR signaling completely blocked ketamine induction of synaptogenesis and behavioral responses in models of depression. Our results demonstrate that these effects of ketamine are opposite to the synaptic deficits that result from exposure to stress and could contribute to the fast antidepressant actions of ketamine.

Schizophrenia, hypocretin (orexin), and the thalamocortical activating system

Diminished connectivity between midline-intralaminar thalamic nuclei and prefrontal cortex has been suggested to contribute to cognitive deficits that are detectable even in early stages of schizophrenia. The midline-intralaminar relay cells comprise the final link in the ascending arousal pathway and are selectively excited by the wake-promoting peptides hypocretin 1 and 2 (orexin A and B). This excitation occurs both at the level of the relay cell bodies and their axon terminals within prefrontal cortex. In rat brain slices, the release of glutamate from midline-intralaminar thalamocortical terminals induces excitatory postsynaptic currents (EPSCs) in layer V pyramidal cells in prefrontal cortex. When hypocretin is infused into medial prefrontal cortex of behaving animals, it improves performance in a complex cognitive task requiring divided attention. Chronic restraint stress causes atrophy of the apical dendritic arbors in layer V prefrontal pyramidal cells and leads to a reduction in hypocretin-induced EPSCs, indicating impairment in excitatory thalamocortical transmission. Thus, taken together with evidence for an underlying loss of excitatory thalamocortical connectivity in schizophrenia, stress in this illness could further exacerbate a breakdown in cortical processing of incoming information from the ascending arousal system.

Role of cAMP response element-binding protein in the rat locus ceruleus: regulation of neuronal activity and opiate withdrawal behaviors

The transcription factor cAMP response element-binding protein (CREB) is implicated in mediating the actions of chronic morphine in the locus ceruleus (LC), but direct evidence to support such a role is limited. Here, we investigated the influence of CREB on LC neuronal activity and opiate withdrawal behaviors by selectively manipulating CREB activity in the LC using viral vectors encoding genes for CREBGFP (wild-type CREB tagged with green fluorescent protein), caCREBGFP (a constitutively active CREB mutant), dnCREBGFP (a dominant-negative CREB mutant), or GFP alone as a control. Our results show that in vivo overexpression of CREBGFP in the LC significantly aggravated particular morphine withdrawal behaviors, whereas dnCREBGFP expression attenuated these behaviors. At the cellular level, CREBGFP expression in the LC in vivo and in vitro had no significant effect on neuronal firing at baseline but enhanced the excitatory effect of forskolin (an activator of adenylyl cyclase) on these neurons, which suggests that the cAMP signaling pathway in these neurons was sensitized after CREB expression. Moreover, in vitro studies showed that caCREBGFP-expressing LC neurons fired significantly faster and had a more depolarized resting membrane potential compared with GFP-expressing control cells. Conversely, LC neuronal activity was decreased by dnCREBGFP, and the neurons were hyperpolarized by this treatment. Together, these data provide direct evidence that CREB plays an important role in controlling the electrical excitability of LC neurons and that morphine-induced increases in CREB activity contribute to the behavioral and neural adaptations associated with opiate dependence and withdrawal.

Arbuscular mycorrhizal fungi associated with the Meliaceae on Hainan island, China

Species richness, spore density, frequency of occurrence, and relative abundance of AM fungi were determined in rhizosphere soil samples from nine tropical rainforest sites on Hainan island, south China, and the arbuscular mycorrhizal (AM) status of members of the Meliaceae was examined. All 28 plant taxa investigated (25 species including two varieties of 1 species and three varieties of another) were colonized by AM fungi. The mean proportion of root length colonized was 56% (range 10-95%). Vesicles were observed in 27 and hyphal coils in 26 of the 28 plant taxa. Mycorrhizas were of the Paris-type or intermediate-type, with no Arum-type mycorrhizas observed. Species richness of AM fungi varied from 3 to 15 and spore density from 46 to 1,499 per 100 g rhizosphere soil. Of 33 AM fungal taxa in five genera isolated and identified, 18 belonged to Glomus, 9 to Acaulospora, 1 to Entrophospora, 2 to Gigaspora, and 3 to Scutellospora. Acaulospora and Glomus were the dominant genera identified. Glomus claroideum was the taxon most commonly isolated, with a frequency of occurrence of 56.5% and relative abundance of 10.4%. A positive correlation was found between percentage of root length colonization and species richness. However, there was no correlation between spore density and percentage of root length colonized by AM fungi.

Somatodendritic autoreceptor regulation of serotonergic neurons: dependence on L-tryptophan and tryptophan hydroxylase-activating kinases

The somatodendritic 5-HT(1A) autoreceptor has been considered a major determinant of the output of the serotonin (5-HT) neuronal system. However, recent studies in brain slices from the dorsal raphe nucleus have questioned the relevance of 5-HT autoinhibition under physiological conditions. In the present study, we found that the difficulty in demonstrating 5-HT tonic autoinhibition in slice results from in vitro conditions that are unfavorable for sustaining 5-HT synthesis. Robust, tonic 5-HT(1A) autoinhibition can be restored by reinstating in vivo 5-HT synthesizing conditions with the initial 5-HT precursor l-tryptophan and the tryptophan hydroxylase co-factor tetrahydrobiopterin (BH(4)). The presence of tonic autoinhibition under these conditions was revealed by the disinhibitory effect of a low concentration of the 5-HT(1A) antagonist WAY 100635. Neurons showing an autoinhibitory response to L-tryptophan were confirmed immunohistochemically to be serotonergic. Once conditions for tonic autoinhibition had been established in raphe slice, we were able to show that 5-HT autoinhibition is critically regulated by the tryptophan hydroxylase-activating kinases calcium/calmodulin protein kinase II (CaMKII) and protein kinase A (PKA). In addition, at physiological concentrations of L-tryptophan, there was an augmentation of 5-HT(1A) receptor-mediated autoinhibition when the firing of 5-HT cells activated with increasing concentrations of the alpha(1) adrenoceptor agonist phenylephrine. Increased calcium influx at higher firing rates, by activating tryptophan hydroxylase via CaMKII and PKA, can work together with tryptophan to enhance negative feedback control of the output of the serotonergic system.

Regulation of RGS proteins by chronic morphine in rat locus coeruleus

The present study explored a possible role for RGS (regulators of G protein signalling) proteins in the long term actions of morphine in the locus coeruleus (LC), a brainstem region implicated in opiate physical dependence and withdrawal. Morphine influences LC neurons through activation of micro -opioid receptors, which, being Gi/o-linked, would be expected to be modulated by RGS proteins. We focused on several RGS subtypes that are known to be expressed in this brain region. Levels of mRNAs encoding RGS2, -3, -4, -5, -7, -8 and -11 are unchanged following chronic morphine, but RGS2 and -4 mRNA levels are increased 2-3-fold 6 h following precipitation of opiate withdrawal. The increases in RGS2 and -4 mRNA peak after 6 h of withdrawal and return to control levels by 24 h. Immunoblot analysis of RGS4 revealed a striking divergence between mRNA and protein responses in LC: protein levels are elevated twofold following chronic morphine and decrease to control values by 6 h of withdrawal. In contrast, levels of RGS7 and -11 proteins, the only other subtypes for which antibodies are available, were not altered by these treatments. Intracellular application of wild-type RGS4, but not a GTPase accelerating-deficient mutant of RGS4, into LC neurons diminished electrophysiological responses to morphine. The observed subtype- and time-specific regulation of RGS4 protein and mRNA, and the diminished morphine-induced currents in the presence of elevated RGS4 protein levels, indicate that morphine induction of RGS4 could contribute to aspects of opiate tolerance and dependence displayed by LC neurons.

Hypocretins (orexins) regulate serotonin neurons in the dorsal raphe nucleus by excitatory direct and inhibitory indirect actions

The hypocretins (hcrt1 and hcrt2) are expressed by a discrete population of hypothalamic neurons projecting to many regions of the CNS, including the dorsal raphe nucleus (DRN), where serotonin (5-HT) neurons are concentrated. In this study, we investigated responses to hcrts in 216 physiologically identified 5-HT and non-5-HT neurons of the DRN using intracellular and whole-cell recording in rat brain slices. Hcrt1 and hcrt2 induced similar amplitude and dose-dependent inward currents in most 5-HT neurons tested (EC50, approximately 250 nm). This inward current was not blocked by the fast Na+ channel blocker TTX or in a Ca2+-free solution, indicating a direct postsynaptic action. The hcrt-induced inward current reversed near -18 mV and was primarily dependent on external Na+ but not on external or internal Ca2+, features typical of Na+/K+ nonselective cation channels. At higher concentrations, hcrts also increased spontaneous postsynaptic currents in 5-HT neurons (EC50, approximately 450-600 nm), which were TTX-sensitive and mostly blocked by the GABA(A) antagonist bicuculline, indicating increased impulse flow in local GABA interneurons. Accordingly, hcrts were found to increase the basal firing of presumptive GABA interneurons. Immunolabeling showed that hcrt fibers projected to both 5-HT and GABA neurons in the DRN. We conclude that hcrts act directly to excite 5-HT neurons primarily via a TTX-insensitive, Na+/K+ nonselective cation current, and indirectly to activate local inhibitory GABA inputs to 5-HT cells. The greater potency of hcrts in direct excitation compared with indirect inhibition suggests a negative feedback function for the latter at higher levels of hcrt activity.

[Suppression of neurotransmitter release by presynaptic metabotropic glutamate receptors]

Activation of ionotropic receptors by glutamate mediates most of the fast excitatory synaptic transmission in mammalian central nervous system. In addition, they are involved in excitotoxic neuronal cell death that occurs in a variety of neurological disorders if these receptors are excessively activated. Metabotropic glutamate receptors (mGluRs) are a G-protein coupled receptor family and they are divided into three groups. Both group II and group III of mGluRs are presynaptically localized on the glutamatergic terminals, and provide a negative feedback to modulate the release of glutamate. Recent data also showed that some mGluRs are presented on non-glutamatergic neurons, such as GABAergic terminals, where mGluRs suppress GABA release when they are activated. Further investigation of mGluRs may lead to the development of novel, safe and effective pharmacological agents to treat a range of neurological disorders and neurodegenerative diseases by preventing the excessive glutamate release.

Hypocretin (orexin) enhances neuron activity and cell synchrony in developing mouse GFP-expressing locus coeruleus

The noradrenergic neurons of the locus coeruleus (LC) play an important role in modulating arousal and selective attention. A similar function has been attributed to the hypocretin neurons of the hypothalamus which maintain a strong synaptic projection to the LC. As the LC can be difficult to detect in the embryonic and neonatal mouse brain, we used a new transgenic mouse with strong GFP expression in the LC under the regulation of a mouse prion promoter. GFP colocalized with immunoreactive tyrosine hydroxylase in sections and dispersed cultures of the LC, allowing visualization and whole cell or single-unit recording from the LC in early stages of cellular development. GFP expression in the LC had no apparent effect on cellular physiology, including resting membrane potential, input resistance, spike threshold, depolarization-induced spike frequency increase, current-voltage relations, or hypocretin responses. In slices of the mature mouse and rat LC, hypocretin-1 and -2 increased spike frequency, with hypocretin-1 being an order of magnitude more potent. In the postnatal day (P) 0-2 developing mouse slice during a developmental period when spikes could be elicited in some cells, other developing LC neurons showed rhythmic, subthreshold oscillations (approximately 1 Hz) in membrane potential (2.9-7.4 mV amplitude); others were arrhythmic. Hypocretin-1 depolarized the membrane potential, resulting in the appearance of spikes in developing LC cells that showed no spikes under control conditions. In the presence of TTX and glutamate receptor antagonists, hypocretin-1-mediated inward currents were blocked by substitution of choline-Cl for NaCl, suggesting an excitatory mechanism based on an inward cation current. Hypocretin-1 initiated strong regular membrane voltage oscillations in arrhythmic immature neurons. Hypocretin increased the temporal synchrony of action potentials studied with dual-cell recording in P1-P5 mouse LC slices, consistent with the view that synchrony of LC output, associated with improved cognitive performance, may be increased by hypocretin. Together these data suggest that the hypothalamus, via hypocretin projections, may therefore be in a position to enhance arousal and modulate plasticity in higher brain centres through the developing LC.

Neurotrophin-3 modulates noradrenergic neuron function and opiate withdrawal

Somatic symptoms and aversion of opiate withdrawal, regulated by noradrenergic signaling, were attenuated in mice with a CNS-wide conditional ablation of neurotrophin-3. This occurred in conjunction with altered cAMP-mediated excitation and reduced upregulation of tyrosine hydroxylase in A6 (locus coeruleus) without loss of neurons. Transgene-derived NT-3 expressed by noradrenergic neurons of conditional mutants restored opiate withdrawal symptoms. Endogenous NT-3 expression, strikingly absent in noradrenergic neurons of postnatal and adult brain, is present in afferent sources of the dorsal medulla and is upregulated after chronic morphine exposure in noradrenergic projection areas of the ventral forebrain. NT-3 expressed by non-catecholaminergic neurons may modulate opiate withdrawal and noradrenergic signalling.

Interrelations of opioids with monoamines in descending inhibition of nociceptive transmission at the spinal level: an immunocytochemical study

This study was designed to reexamine a previous proposal of whether the opioid-like substances (OLS) being acting mainly as an intrinsic spinal mediator in the descending inhibition of nociception of the bulbospinally projecting NE-ergic, and/or 5-HT-ergic terminals in the dorsal horn by using an immunocytochemical method. The effects of intrathecal (i.t.) phentolamine (Ph), cyproheptadine (Cyp), and naloxone (Nal), administered separately or coadministered by two of them, on the expression of Fos-like-immunoreactive (FLI) neurons were observed on both sides of the lumbar dorsal horn of rats, in which equal volumes of formalin were injected into two hindpaws and the ipsilateral dorsolateral funiculus (DLF) was transected at the thoracic level antecedently. The results showed: (1) when rats were pretreated with i.t. saline, the number of nociceptive FLI neurons was significantly lowered 44% (p<0.01) on the side of the lumbar dorsal horn with intact DLF compared to the opposite side with sectioned DLF; (2) when rats were separately pretreated with i.t. Ph, Cyp and Nal, the reduction of FLI neurons on the DLF-intact side were decreased by 27% (p<0.01), 21% (p<0.01), and 25% (p<0.01), respectively; (3) when rats were pretreated with combined i.t. Ph+Cyp, the reduction on the intact side was eliminated almost completely (4%); (4) when rats were pretreated with combined i.t. Ph+Nal, the reduction on the intact side was 21% (p<0.01); and (5) when rats were pretreated with i.t. Cyp+Nal, the reduction on the intact side was 9.1%. These results suggest that: (1) nearly all the suppressive action exerted by the DLF-descending fibers are produced by the release of either NE or 5-HT as neurotransmitters at the spinal level; (2) most of the opioid-like substances act as an intrinsic spinal mediator mainly for the descending NE-ergic, but in a lesser extent for the 5-HT-ergic terminals in the dorsal horn circuitry; and (3) some OLS-ergic interneurons may only be activated by local nociceptive input.

Nociceptive c-fos expression in supraspinal areas in avoidance of descending suppression at the spinal relay station

The number and distribution of Fos-like-immunoreactive neurons in different supraspinal brain areas induced by formalin injection into one hindpaw was estimated in rats with transected dorsal half of the spinal cord at the thoracic level in an attempt to avoid most of the descending modulatory actions. The results showed that: (i) after spinal lesion, the peripheral noxious inputs, going up mainly through the ventral spinal cord, elicited a more widespread and densely located Fos-like-immunoreactive neurons in subcortical areas, many of them showed no Fos expression when noxious stimulation was given in rats with intact spinal cord; (ii) at the same time, a small number of subcortical areas, such as the lateral ventroposterior thalamic nucleus and dorsal raphe nucleus, exhibited no significant increase of nociceptive Fos-like immunoreactive neurons after spinal lesion as compared to that with intact spinal cord; and (iii) there appeared a prominent expansion of cortical areas with densely located Fos-like-immunoreactive neurons in spinal-lesioned rats as compared with the limited labelled areas in the control group with intact spinal cord. These results indicate that: (i) in avoiding the spinally descending modulatory mechanisms, more widespread supraspinal and cortical neurons will be recruited and activated in response to the noxious stimulation; and (ii) the descending systems exert differential actions on the spinal targets which project nociceptive signals to different supraspinal regions. The implication of these facts is discussed.

Effects of intrathecal monoamine antagonists on the nociceptive c-Fos expression in a lesioned rat spinal cord

Effects of intrathecal (i.t.) administration of monoamine antagonists on formalin-induced neuronal c-Fos expression in two sides of the lumbar dorsal horn were observed in rats with unilateral transection of the dorsolateral funiculus at T11-12 level. The results showed that: 1) pretreated with i.t. normal saline (control) and then an equal volume of formalin was injected into the two hindpaws, the number of Fos-like immunoreactive neurons were 44% lower on the side of lumbar dorsal horn with intact dorsolateral funiculus (57 +/- 3.1 vs. 103 +/- 3.8). 2) Pretreatment with i.t. phentolamine (a non-selective alpha-adrenoceptor antagonist) caused an increase of Fos-like immunoreactive neurons on the intact side so showing only a reduction rate of 23% to the lesioned side (p < .01); 3) pretreatment with i.t. cyproheptadine (a 5-HT-receptor antagonist) caused a similar reduction rate of 21% (p < .01) of Fos-like immunoreactive neurons on the intact side; and 4) combined i.t. pretreatment with phentolamine and cyproheptadine caused a reduction of Fos-like immunoreactive neurons of only 4% on the intact side, namely, the differences in the number of Fos-like immunoreactive neurons on two sides of the lumbar spinal cord owing to the unilateral dorsolateral funiculus lesion were nearly abolished by i.t. coinjection of phentolamine and cyproheptadine. The results indicate that 1) peripheral noxious inputs can provoke a spinally-descending inhibitory effect on the spinal nociceptive transmission via the dorsolateral funiculus and 2) the descending fibers in dorsolateral funiculus exert their action mainly through the release of either norepinephrine or 5-HT at the spinal level.

Peripheral NMDA receptors contribute to activation of nociceptors: a c-fos expression study in rats

By using immunocytochemical techniques, we demonstrated that: (1) unilateral injection of N-methyl-D-aspartate (NMDA; 10, 20, 50 micromol) into the plantar aspect of hindpaw of the normal waked rats elicited a dose-dependent increase of c-fos expression in the superficial laminae on the side of the spinal dorsal horn ipsilateral to the injection; (2) combined injection of MK-801, a non-competitive NMDA receptor antagonist, with formalin into the hindpaw could suppress formalin-induced c-fos expression in the dorsal horn, with a stronger suppression after higher doses of MK-801 being injected. These results strongly suggest that NMDA receptors might be located in the membrane of peripheral axonal terminals of the dorsal root ganglion neurons and might be involved in the activation of nociceptors.

Changes in the resistance of Plasmodium falciparum to chloroquine in Hainan, China

In 1979, in view of the widespread resistance of Plasmodium falciparum to chloroquine in the island of Hainan, China, it use as an antimalarial was suspended throughout the island. A longitudinal survey of the chloroquine-sensitivity of P. falciparum was carried out over the period 1981-91 to investigate whether its resistance had changed from the 1979 level. In-vitro assays were carried out every 2-3 years, while in-vivo tests were performed annually over the period 1981-83 and also in 1991. Resistance to chloroquine declined progressively after its use had stopped. The in-vitro tests indicated that the rate of chloroquine-resistant P. falciparum was 97.9% in 1981, but dropped to 60.9% in 1991 (P < 0.001). The mean concentration of chloroquine for complete inhibition of schizont formation was 10.4 pmol/microliters in 1981, but decreased to 3.0 pmol/microliters in 1991 (P < 0.001). The proportion of samples taken from malaria cases that required high concentrations ( > 6.4 pmol/microliters) of chloroquine for complete inhibition of schizont formation was 83.3% in 1981, but only 17.4% in 1991 (P < 0.001); at low concentrations ( > 1.6 pmol/microliters), the corresponding proportions increased from 4.2% in 1981 to 60.8% in 1991 (P < 0.001). In the 4-week in-vivo test, the rate of chloroquine-resistant P. falciparum decreased from 84.2% in 1981 to 40% in 1991 (P < 0.001). RII + RIII cases represented 59.4% of the total resistant cases in 1981, but decreased to 37.5% in 1991 (0.02 > P > 0.01).

Chemotherapy outcomes in advanced non-small-cell lung carcinoma

Despite 20 years of chemotherapy trials in advanced NSCLC, optimal regimens leading to complete remissions have not been identified. The decision to treat a patient who has inoperable advanced NSCLC must take into account the toxicity of the chemotherapy. The toxicities most often reported are myelosuppression and emesis; however, these trials were performed before the use of colony-stimulating factors (ie, granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor) and serotonin antagonists (ie, ondansetron). Granulocyte colony-stimulating factor has been shown to shorten the duration of neutropenia and thus decrease the incidence of confirmed infections. Colony-stimulating factors also may allow significant escalation of the dose of chemotherapy. Ondansetron has been shown to ameliorate cisplatin-induced emesis better than other antiemetics. The performance status of a patient has been noted to be a predictor for survival, as well as response to therapy, and this should also be taken into consideration when deciding to treat a patient with advanced inoperable NSCLC. Ideally, patients with stage IV NSCLC should be placed on investigational therapy protocols to identify optimally active combinations of agents. One approach to the patient with inoperable NSCLC who is ineligible for a trial, or who does not wish to participate in a trial, is to offer chemotherapy soon after diagnosis, as patients in this category are likely to be less symptomatic and have optimal performance status. A platinum-containing regimen would seem to be the most reasonable regimen in such a patient. It is hoped that ongoing trials in suitable candidates will lead to the identification of more consistently active agents to deal with this devastating disease.

Plasminogen activator inhibitor-1 mRNA is expressed in platelets and megakaryocytes and the megakaryoblastic cell line CHRF-288

Plasminogen activator inhibitor-1 (PAI-1) is present in the platelet alpha-granule and is released on platelet activation. Platelet PAI-1 could either be synthesized by the megakaryocyte or taken up from the plasma. In this report we confirm the presence of PAI-1 protein in human megakaryocytes by Western blot analysis and show its synthesis in guinea pig megakaryocytes by metabolic labeling. We document the presence of PAI-1 mRNA in human platelets and show a 3-kb mRNA species on Northern blot analysis of guinea pig megakaryocytes. Neither untreated CHRF-288 cells, a megakaryoblastic cell line, nor human erythroleukemia (HEL) cells expressed PAI-1 mRNA. Phorbol ester (phorbol 12-myristate 13-acetate, 160 nM) treatment of CHRF-288 and HEL cells for 4 days induced PAI-1 mRNA expression in CHRF-288 cells but not in HEL cells. These studies show that PAI-1 is synthesized by megakaryocytes. Megakaryocytes most likely determine the PAI-1 content of platelets and thereby establish the antifibrinolytic potential of the platelet.

[Effect of increasing amounts of clonidine during hyperbaric tetracaine spinal anesthesia]

The effect of adding clonidine to hyperbaric tetracaine spinal anesthesia was investigated in 60 ASA class I-II patients scheduled for orthopedic and lower abdominal surgery. The subjects were randomly allocated into 4 groups. All patients received tetracaine 10 mg in 10% glucose solution 2 mL. Patients in group 1 received above medication and were the control group, patients in the other groups received tetracaine plus increasing dosages of clonidine: 15 microgram (Gr.2), 30 microgram (Gr.3), and 45 microgram (Gr.4). The segmental level of sensory loss was tested by the pinprick method using a 23 G needle. The three clonidine groups had significantly increased in the sensory regression time to L1 level (by 42, 47, 60% respectively), and also had significantly increased motor complete recovery time (by 48, 70, 74% respectively), but the incidence of hypotension and bradycardia was increased in the clonidine 0.045 mg group. It is concluded that addition of 15 or 30 microgram clonidine may be useful as a means of increasing the duration of hyperbaric tetracaine spinal anesthesia.