GluD1, linked to schizophrenia, controls the burst firing of dopamine neurons.

Human mutations of the GRID1 gene encoding the orphan delta1 glutamate receptor-channel (GluD1) are associated with schizophrenia but the explicit role of GluD1 in brain circuits is unknown. Based on the known function of its paralog GluD2 in cerebellum, we searched for a role of GluD1 in slow glutamatergic transmission mediated by metabotropic receptor mGlu1 in midbrain dopamine neurons, whose dysfunction is a hallmark of schizophrenia. We found that an mGlu1 agonist elicits a slow depolarizing current in HEK cells co-expressing mGlu1 and GluD1, but not in cells expressing mGlu1 or GluD1 alone. This current is abolished by additional co-expression of a dominant-negative GluD1 dead pore mutant. We then characterized mGlu1-dependent currents in dopamine neurons from midbrain slices. Both the agonist-evoked and the slow postsynaptic currents are abolished by expression of the dominant-negative GluD1 mutant, pointing to the involvement of native GluD1 channels in these currents. Likewise, both mGlu1-dependent currents are suppressed in GRID1 knockout mice, which reportedly display endophenotypes relevant for schizophrenia. It is known that mGlu1 activation triggers the transition from tonic to burst firing of dopamine neurons, which signals salient stimuli and encodes reward prediction. In vivo recordings of dopamine neurons showed that their spontaneous burst firing is abolished in GRID1 knockout mice or upon targeted expression of the dominant-negative GluD1 mutant in wild-type mice. Our results de-orphanize GluD1, unravel its key role in slow glutamatergic transmission and provide insights into how GRID1 gene alterations can lead to dopaminergic dysfunctions in schizophrenia.

Nicotine consumption is regulated by a human polymorphism in dopamine neurons.

Smoking is the most important preventable cause of morbidity and mortality worldwide. Recent genome-wide association studies highlighted a human haplotype on chromosome 15 underlying the risk for tobacco dependence and lung cancer. Several polymorphisms in the CHRNA3-CHRNA5-CHRNB4 cluster coding for the nicotinic acetylcholine receptor (nAChR) α3, α5 and ß4 subunits were implicated. In mouse models, we define a key role in the control of sensitivity to nicotine for the α5 subunit in dopaminergic (DAergic) neurons of the ventral tegmental area (VTA). We first investigated the reinforcing effects of nicotine in drug-naive α5(-/-) mice using an acute intravenous nicotine self-administration task and ex vivo and in vivo electrophysiological recordings of nicotine-elicited DA cell activation. We designed lentiviral re-expression vectors to achieve targeted re-expression of wild-type or mutant α5 in the VTA, in general, or in DA neurons exclusively. Our results establish a crucial role for α5*-nAChRs in DAergic neurons. These receptors are key regulators that determine the minimum nicotine dose necessary for DA cell activation and thus nicotine reinforcement. Finally, we demonstrate that a single-nucleotide polymorphism, the non-synonymous α5 variant rs16969968, frequent in many human populations, exhibits a partial loss of function of the protein in vivo. This leads to increased nicotine consumption in the self-administration paradigm. We thus define a critical link between a human predisposition marker, its expression in DA neurons and nicotine intake.

Co-activation of VTA DA and GABA neurons mediates nicotine reinforcement.

Smoking is the most important preventable cause of mortality and morbidity worldwide. This nicotine addiction is mediated through the nicotinic acetylcholine receptor (nAChR), expressed on most neurons, and also many other organs in the body. Even within the ventral tegmental area (VTA), the key brain area responsible for the reinforcing properties of all drugs of abuse, nicotine acts on several different cell types and afferents. Identifying the precise action of nicotine on this microcircuit, in vivo, is important to understand reinforcement, and finally to develop efficient smoking cessation treatments. We used a novel lentiviral system to re-express exclusively high-affinity nAChRs on either dopaminergic (DAergic) or γ-aminobutyric acid-releasing (GABAergic) neurons, or both, in the VTA. Using in vivo electrophysiology, we show that, contrary to widely accepted models, the activation of GABA neurons in the VTA plays a crucial role in the control of nicotine-elicited DAergic activity. Our results demonstrate that both positive and negative motivational values are transmitted through the dopamine (DA) neuron, but that the concerted activity of DA and GABA systems is necessary for the reinforcing actions of nicotine through burst firing of DA neurons. This work identifies the GABAergic interneuron as a potential target for smoking cessation drug development.

The cardioprotectant 3',4'-dihydroxyflavonol inhibits opening of the mitochondrial permeability transition pore after myocardial ischemia and reperfusion in rats.

The study aimed to determine the effect of 3',4'-dihydroxyflavonol (DiOHF) on mitochondrial function, in particular opening of the mitochondrial permeability transition pore (mPTP), respiratory function and reactive oxygen species (ROS) production, in isolated cardiac mitochondria after coronary artery occlusion and reperfusion in vivo. Opening of the mPTP, oxygen consumption and ROS production (assessed by measurement of H2O2) was determined in mitochondria isolated from normal hearts or from the ischemic zone of rat hearts subjected to 30min coronary artery occlusion and 15min reperfusion. Treatment of sham rats with DiOHF (10mgkg(-1) iv) significantly increased the concentration of Ca(2+) required to stimulate mPTP opening. This was accompanied by increased state 3 oxygen consumption and decreased H2O2 release. Ischemia and reperfusion (IR) significantly decreased the concentration of Ca(2+) required to stimulate mPTP opening, decreased state 3 oxygen consumption and increased H2O2 release, when pyruvate plus malate was provided as a substrate. Treatment with DiOHF prevented IR-induced changes in mPTP opening, state 3 oxygen consumption and H2O2 release so that there was no difference compared to sham. In isolated cardiac mitochondria from normal rats DiOHF had no effect on mPTP opening or on state 3 respiration but caused a small increase in state 4 respiration and decreased the respiratory control ratio. DiOHF, administered during ischemia just before reperfusion, inhibits mPTP opening and preserves mitochondrial function through a mechanism likely to be independent of its antioxidant activity or any direct effect on the mPTP.

[Guillain-Barré syndrome heralding acute query fever]. / Syndrome de Guillain-Barré révélant une fièvre Q aiguë.

INTRODUCTION: Q fever is a polymorphic disease, which can induce neurological disturbances. The central nervous system is mainly involved while peripheral neuropathies are rare with less than 15 cases reported in the literature. CASE-REPORT: We report here a case of acute polyradiculoneuritis associated with acute Q fever, with favorable outcome after antibiotic and intravenous immunoglobulin therapies. CONCLUSION: Serologic tests for Coxiella burnetii should be performed in case of unusual polyradiculoneuritis with fever, headache and neuro-ophthalmologic disorders, even when environmental exposure is lacking, because Q fever requires specific antibiotic treatment and serological follow-up.

Ultrafast and whole-body cooling with total liquid ventilation induces favorable neurological and cardiac outcomes after cardiac arrest in rabbits.

BACKGROUND: In animal models of cardiac arrest, the benefit afforded by hypothermia is closely linked to the rapidity of the decrease in body temperature after resuscitation. Because total liquid ventilation (TLV) with temperature-controlled perfluorocarbons induces a very rapid and generalized cooling, we aimed to determine whether this could limit the post-cardiac arrest syndrome in a rabbit model. We especially focused on neurological, cardiac, pulmonary, liver and kidney dysfunctions. METHODS AND RESULTS: Anesthetized rabbits were submitted to either 5 or 10 minutes of untreated ventricular fibrillation. After cardiopulmonary resuscitation and resumption of a spontaneous circulation, the animals underwent either normothermic life support (control) or therapeutic hypothermia induced by TLV. The latter procedure decreased esophageal and tympanic temperatures to 32°C to 33°C within only 10 minutes. After rewarming, the animals submitted to TLV exhibited an attenuated neurological dysfunction and decreased mortality 7 days later compared with control. The neuroprotective effect of TLV was confirmed by a significant reduction in brain histological damages. We also observed limitation of myocardial necrosis, along with a decrease in troponin I release and a reduced myocardial caspase 3 activity, with TLV. The beneficial effects of TLV were directly related to the rapidity of hypothermia induction because neither conventional cooling (cold saline infusion plus external cooling) nor normothermic TLV elicited a similar protection. CONCLUSIONS: Ultrafast cooling instituted by TLV exerts potent neurological and cardiac protection in an experimental model of cardiac arrest in rabbits. This could be a relevant approach to provide a global and protective hypothermia against the post-cardiac arrest syndrome.

Mycophenolate as induction therapy in lupus nephritis with renal function impairment.

BACKGROUND: Mycophenolate (MF) is effective as induction therapy for lupus nephritis (LN) in patients with normal renal function; however, little is known about its role in patients with impaired renal failure. The purpose of this study was to evaluate the response to MF in LN and its association with baseline renal function. METHODS: Data were obtained for 90 patients from 12 Spanish renal units who were receiving MF as induction therapy for LN. Patients were classified into 2 groups: group 1 (estimated glomerular filtration rate [eGFR] ≥60 ml/min/1.73 m(2)) and group 2 (eGFR <60 ml/min/ 1.73 m(2)). The primary outcome measure was the percentage of patients who achieved any response and its relationship with initial eGFR. The secondary outcome measures were the percentage of patients who achieved a complete response (CR) or partial response (PR) and the appearance of relapses during treatment and side effects. RESULTS: At initiation of MF treatment, there were no differences in the main parameters between group 1 (n = 63; eGFR 87 ± 23 ml/min/ 1.73 m(2)) and group 2 (n = 27; eGFR 44 ± 12 ml/min/1.73 m(2)). Exposure to prednisone and MF was similar. The percentages of patients who achieved a response in groups 1 and 2 were, respectively, 69.2 and 43.8% at 6 months and 81.3 and 73.7% at 12 months. CR was more frequent in group 1, whereas PR was similar in both groups. Four patients relapsed and side effects were unremarkable. CONCLUSIONS: MF is effective and safe as induction therapy for LN, and response is even achieved in patients with baseline renal impairment.

Observational study of a series of basal cell carcinomas: Evaluation of location as a risk factor for recurrence.

Basal cell carcinoma (BCC) is locally aggressive and its prognosis depends on the risk of recurrence. The initial location of the tumor is a key criterion for calculating the risk of recurrence. The aim of this study was to evaluate the sites that appear to be most at risk of recurrence of BCC. All cases of BCC analyzed at the anatomopathology laboratory of the University Hospital of Montpellier for 1 year were retrospectively included. In case of recurrence on the same site, only carcinomas that had previously been completely removed were analyzed. Among 803 BCC, 37 (4.6%) were confirmed as recurrent, including 34 (92%) on the head. The locations statistically at higher risk of recurrence were the temporal and frontal/temporal areas (32.4%), the medial canthus and lower eyelid area (18.9%), the ala and tip of the nose (16.2%), and the ears (8.1%). The frontal/temporal regions appear to be an area of major interest in this series. A high risk of recurrence was confirmed in the periorificial locations for the ear, the nose, and periorbital area, but not for the perioral area. In addition, the entire nose did not appear to be at risk, only the tip and the ala.

Nicotine reinforcement and cognition restored by targeted expression of nicotinic receptors.

Worldwide, 100 million people are expected to die this century from the consequences of nicotine addiction, but nicotine is also known to enhance cognitive performance. Identifying the molecular mechanisms involved in nicotine reinforcement and cognition is a priority and requires the development of new in vivo experimental paradigms. The ventral tegmental area (VTA) of the midbrain is thought to mediate the reinforcement properties of many drugs of abuse. Here we specifically re-expressed the beta2-subunit of the nicotinic acetylcholine receptor (nAChR) by stereotaxically injecting a lentiviral vector into the VTA of mice carrying beta2-subunit deletions. We demonstrate the efficient re-expression of electrophysiologically responsive, ligand-binding nicotinic acetylcholine receptors in dopamine-containing neurons of the VTA, together with the recovery of nicotine-elicited dopamine release and nicotine self-administration. We also quantified exploratory behaviours of the mice, and showed that beta2-subunit re-expression restored slow exploratory behaviour (a measure of cognitive function) to wild-type levels, but did not affect fast navigation behaviour. We thus demonstrate the sufficient role of the VTA in both nicotine reinforcement and endogenous cholinergic regulation of cognitive functions.