Mitochondrial Metabolism in Major Depressive Disorder: From Early Diagnosis to Emerging Treatment Options.

Major Depressive Disorder (MDD) is one of the most disabling diseases in the world. MDD is traditionally diagnosed based on a patient's symptoms, which can lead to misdiagnosis. Although the pathogenic mechanisms of MDD are unknown, several studies have identified mitochondrial dysfunction as a central factor in the onset and progression of MDD. In the context of MDD, alterations in mitochondrial metabolism can lead to imbalances in energy production and oxidative stress, contributing to the disorder´s underlying pathophysiological mechanisms. Consequently, the identification of mitochondrial dysfunction as a key biomarker for early and accurate diagnosis of MDD represents a significant challenge. Faced with the limits of traditional treatments with antidepressants, new pharmacological therapeutic targets are being investigated such as ketamine/esketamine, psychedelics, or anti-inflammatories. All of these drugs show potential antidepressant effects due to their speed of action and ability to modulate neuroplasticity and/or motor processing. In parallel, non-pharmacological therapeutic targets are studied, like Transcranial Magnetic Stimulation (TMS) and Deep Brain Stimulation (DBS), recognized for their ability to modulate neuronal activity and offer treatment alternatives. As cellular activity is directly related to mitochondrial respiration, the aim of this review is examining the link between mitochondrial dysfunction and MDD, assessing how mitochondrial biomarkers could provide a more objective and precise diagnostic tool, and exploring other treatments in addition to traditional antidepressants, with a specific focus on emerging therapeutic targets. Finally, a detailed analysis of the strengths, weaknesses, opportunities, and threats of these approaches was carried out, highlighting the key challenges that must be addressed.

Strategies to Improve Therapeutic Adherence in Polymedicated Patients over 65 Years: A Systematic Review and Meta-Analysis.

BACKGROUND: Part of the population over 65 years of age suffer from several pathologies and are therefore polymedicated. In this systematic review and metanalysis, we aimed to determine the efficacy of several strategies developed to improve adherence to pharmacological treatment in polymedicated elderly people. DESIGN: Web Of Science, PubMed and the Cochrane Library were searched until 2 January 2024. In total, 17 of the 1508 articles found evaluated the efficacy of interventions to improve adherence to medication in polymedicated elderly patients. Methodological quality and the risk of bias were rated using the Cochrane risk of bias tool. Open Meta Analyst® software was used to create forest plots of the meta-analysis. RESULTS: In 11 of the 17 studies, an improvement in adherence was observed through the use of different measurement tools and sometimes in combination. The most frequently used strategy was using instructions and counselling, always in combination, in a single strategy used to improve adherence; one involved the use of medication packs and the other patient follow-up. In both cases, the results in improving adherence were positive. Five studies using follow-up interventions via visits and phone calls showed improved adherence on the Morisky Green scale compared to those where usual care was received [OR = 1.900; 95% CI = 1.104-3.270] (p = 0.021). DISCUSSION: There is a high degree of heterogeneity in the studies analyzed, both in the interventions used and in the measurement tools for improving adherence to treatment. Therefore, we cannot make conclusions about the most efficacious strategy to improve medication adherence in polymedicated elderly patients until more evidence of single-intervention strategies is available.

Neuroinflammation in the Evolution of Motor Function in Stroke and Trauma Patients: Treatment and Potential Biomarkers.

Neuroinflammation has a significant impact on different pathologies, such as stroke or spinal cord injury, intervening in their pathophysiology: expansion, progression, and resolution. Neuroinflammation involves oxidative stress, damage, and cell death, playing an important role in neuroplasticity and motor dysfunction by affecting the neuronal connection responsible for motor control. The diagnosis of this pathology is performed using neuroimaging techniques and molecular diagnostics based on identifying and measuring signaling molecules or specific markers. In parallel, new therapeutic targets are being investigated via the use of bionanomaterials and electrostimulation to modulate the neuroinflammatory response. These novel diagnostic and therapeutic strategies have the potential to facilitate the development of anticipatory patterns and deliver the most beneficial treatment to improve patients' quality of life and directly impact their motor skills. However, important challenges remain to be solved. Hence, the goal of this study was to review the implication of neuroinflammation in the evolution of motor function in stroke and trauma patients, with a particular focus on novel methods and potential biomarkers to aid clinicians in diagnosis, treatment, and therapy. A specific analysis of the strengths, weaknesses, threats, and opportunities was conducted, highlighting the key challenges to be faced in the coming years.

Safe Care and Medication Intake Provided by Caregivers at Home: Reality Care Study Protocol.

JUSTIFICATION: Providing care to patients with several conditions and simultaneously taking several medications at home is inexorably growing in developed countries. This trend increases the chances of home caregivers experiencing diverse errors related with medication or care. OBJECTIVE: To determine the effectiveness of four different educational solutions compared to the natural intervention (absence of intervention) to provide a safer care at home by caregivers. METHOD: Prospective, parallel, and mixed research study with two phases. Candidates: Home-based caregivers caring a person with multiple comorbid conditions or polymedication who falls into one of the three profiles of patients defined for the study (oncology, cardiovascular, or pluripathological patients). First phase: Experts first answered an online survey, and then joined together to discuss the design and plan the content of educational solutions directed to caregivers including the identification of medication and home care errors, their causes, consequences, and risk factors. Second phase: The true experiment was performed using an inter- and intrasubject single-factor experimental design (five groups: four experimental groups against the natural intervention (control), with pre- and post-intervention and follow-up measures) with a simple random assignment, to determine the most effective educational solution (n = 350 participants). The participants will be trained on the educational solutions through 360 V, VR, web-based information, or psychoeducation. A group of professionals called the "Gold Standard" will be used to set a performance threshold for the caring or medication activities. The study will be carried out in primary care centers, hospitals, and caregivers' associations in the Valencian Community, Andalusia, Madrid, and Murcia. EXPECTED RESULTS: We expect to identify critical elements of risk management at home for caregivers and to find the most effective and optimal educational solution to reduce errors at home, increasing caregivers' motivation and self-efficacy whilst the impact of gender bias in this activity is reduced. TRIAL REGISTRATION: Clinical Trial NCT05885334.

Inhaled Loxapine as a Rapid Treatment for Agitation in Patients with Personality Disorder: A Prospective Study on the Effects of Time.

Objective: Agitation in patients diagnosed with personality disorders (PD) is one of the most frequent crises in emergency departments (ED). Although many medications have been tested, their effectiveness has been small or non-significant, and no specific drugs are supported by the available evidence. This study aimed to evaluate the efficacy of Inhaled loxapine (IL) as a therapeutic option for agitated patients with PD. Methods: A naturalistic, unicentric, prospective study was carried out. Thirty subjects diagnosed with PD and attending the ED with episodes of agitation were recruited most of whom were women diagnosed with Borderline Personality Disorder. Subjects were treated with a single dose of IL (9.1 mg). Efficacy was assessed with the Clinical Global Impression scale, the Excited Component of the Positive and Negative Syndrome Scale (PANSS-EC) and the Agitation-Calmness Evaluation Scale (ACES). Patients were followed 60 minutes after administration to measure IL effect and its duration. Results: IL exhibited an overall efficacy in managing mild to severe agitation, with a quick onset of effect and persistence. 'Effect of time', where IL efficacy is maintained over time, is more marked in higher-severity agitation. No additional treatments were needed to improve agitation during the follow-up time. Conclusion: Results suggest that IL could be a safe and effective option to manage agitation in PD.

Analysis of Mitochondrial Function in Cell Membranes as Indicator of Tissue Vulnerability to Drugs in Humans.

Drug side effects are one of the main reasons for treatment withdrawal during clinical trials. Reactive oxygen species formation is involved in many of the drug side effects, mainly by interacting with the components of the cellular respiration. Thus, the early detection of these effects in the drug discovery process is a key aspect for the optimization of pharmacological research. To this end, the superoxide formation of a series of drugs and compounds with antidepressant, antipsychotic, anticholinergic, narcotic, and analgesic properties was evaluated in isolated bovine heart membranes and on cell membrane microarrays from a collection of human tissues, together with specific inhibitors of the mitochondrial electron transport chain. Fluphenazine and PB28 promoted similar effects to those of rotenone, but with lower potency, indicating a direct action on mitochondrial complex I. Moreover, nefazodone, a drug withdrawn from the market due to its mitochondrial hepatotoxic effects, evoked the highest superoxide formation in human liver cell membranes, suggesting the potential of this technology to anticipate adverse effects in preclinical phases.

Study of Tissue-Specific Reactive Oxygen Species Formation by Cell Membrane Microarrays for the Characterization of Bioactive Compounds.

The production of reactive oxygen species (ROS) increases considerably in situations of cellular stress, inducing lipid peroxidation and multiple alterations in proteins and nucleic acids. However, sensitivity to oxidative damage varies between organs and tissues depending on the triggering process. Certain drugs used in the treatment of diverse diseases such as malaria have side effects similar to those produced by oxidative damage, although no specific study has been conducted. For this purpose, cell membrane microarrays were developed and the superoxide production evoked by the mitochondrial activity was assayed in the presence of specific inhibitors: rotenone, antimycin A and azide. Once the protocol was set up on cell membrane isolated from rat brain areas, the effect of six antimalarial drugs (atovaquone, quinidine, doxycycline, mefloquine, artemisinin, and tafenoquine) and two essential oils (Rosmarinus officinalis and Origanum majoricum) were evaluated in multiple human samples. The basal activity was different depending on the type of tissue, the liver, jejunum and adrenal gland being the ones with the highest amount of superoxide. The antimalarial drugs studied showed specific behavior according to the type of human tissue analyzed, with atovaquone and quinidine producing the highest percentage of superoxide formation, and doxycycline the lowest. In conclusion, the analysis of superoxide production evaluated in cell membranes of a collection of human tissues allowed for the characterization of the safety profile of these antimalarial drugs against toxicity mediated by oxidative stress.

Efficacy of Acetylcholinesterase Inhibitors on Cognitive Function in Alzheimer's Disease. Review of Reviews.

Alzheimer's disease (AD) is the most common form of dementia over the age of 65. It is estimated that 115.4 million people will be affected by AD by 2050. Acetylcholinesterase inhibitors (AChEI) are the only available and approved treatment for AD. The aim of the present study was to analyse the evidence on the efficacy of the AChEI in the treatment of cognitive symptoms of Alzheimer's disease. For that purpose, a review of review of the systematic reviews (SRs) on this topic was carried out by Web of Science, PubMed, and The Cochrane Library, among others, were searched until 24 September 2021. Thirteen of the 1773 articles evaluated the efficacy of AChEI on cognitive function and/or general condition and/or behavioural disturbances of patients with mild to moderate AD. Methodological quality and risk of bias were rated using the ROBIS scale. The quality of the identified studies was high for nine of them, unclear for two, and finally only in two of the 13 studies did we detect low quality. Overall, AChEI showed very low efficacy in improving cognition in patients with mild to moderate AD. Better results were obtained in improving global state, with donepezil being the most effective treatment. No improvements in behavioural disturbances were found. Few high-quality reviews provide clear evidence of the effects of AChEI on cognition, global change, behaviour, and mortality. The data suggest that AChEI stabilize or slow cognitive deterioration, improving global status. In addition, data indicate that the use of AChEI decreases mortality in patients with mild to moderate AD. However, there is no evidence that they improve patient behaviour. Donepezil is the best therapeutic alternative at a dose of 10 mg/day.

Trabajando la relación Universidad-sociedad. Abordaje multidisciplinar y difusión social / Working the University-Society relationship. Multidisciplinary approach and social diffusion

INTRODUCCIÓN: La transferencia del conocimiento a la sociedad es una de las funciones importantes de la Universidad, lo que implica el uso de un lenguaje y unos medios adecuados hacia los diferentes colectivos de la sociedad, atendiendo a grupos de edad y situaciones socioeconómicas diversas. MATERIALES Y MÉTODOS: A través de las competencias transversales de cada grado, competencias genéricas que se relacionan con la puesta en práctica de una forma integrada de aptitudes, conocimientos y valores adquiridos, se ha realizado este proyecto de innovación docente con alumnado de la Universidad del País Vasco/Euskal Herriko Unibertsitatea. En él se han trabajado las habilidades del alumnado en el uso de diferentes registros de comunicación oral y escritura según la audiencia hacia la que se dirigen. Este trabajo se ha realizado dentro de un equipo multidisciplinar, de forma que el alumnado ha podido conocer y afrontar problemas de salud que requieren una actuación conjunta con otros profesionales del ámbito sanitario y científico. RESULTADOS Y CONCLUSIÓN: Esta interacción entre alumnado de diferentes grados ha permitido su enriquecimiento, proporcionándoles una visión más amplia de lo que pueden aportar los diferentes profesionales frente al mismo problema o reto. Desde este proyecto se ha planteado, a través de metodologías activas, favorecer la interacción entre los futuros profesionales de diferentes disciplinas y concienciar de la importancia de la transmisión de conocimiento a la sociedad, creando redes que contribuyan a la innovación y transferencia

INTRODUCTION: The transfer of knowledge to society is one of the important functions of the university, which implies the use of an appropriate language and means towards the different groups of society, attending to age groups and diverse socio-economic situations. MATERIALS AND METHODS: Through the transversal competences of each Degree, generic competences that are related to the implementation of an integrated form of acquired skills, knowledge and values, this teaching innovation project has been carried out with students from the University of The Basque Country (UPV / EHU). Thus, the student's abilities in the use of different oral and written communication registers according to the target audience have been studied. This work has been carried out within a multidisciplinary team, in such a way that the student has been able to know and face health problems that require joint action with other professionals in the health and scientific field. RESULTS AND CONCLUSION: This interaction among students of different degrees has allowed their enrichment, providing them with a broader vision of what different professionals can contribute to the same problem or challenge. From this project, it has been proposed, through active methodologies, to promote interaction between future professionals from different disciplines, and to raise awareness of the importance of the transmission of knowledge to society, creating networks that contribute to innovation and transfer

Ketamine promotes rapid and transient activation of AMPA receptor-mediated synaptic transmission in the dorsal raphe nucleus.

Accumulating evidence indicates that the antidepressant effects of ketamine are, in part, mediated by an increase in the AMPA receptor-mediated neurotransmission in depression related areas, such as the prefrontal cortex (PFC). Therefore, activity in PFC-projecting areas related to major depression, such as the dorsal raphe nucleus (DR), may also be modulated by ketamine. We used whole-cell patch-clamp recordings and western blot experiments to determine whether ketamine promotes acute and maintained alterations in glutamatergic transmission and mTOR pathway in the DR. Bath perfusion of ketamine, but not the NMDA receptor antagonist D-AP5, increased the frequency of AMPA receptor-mediated spontaneous EPSCs (sEPSCs) in DR neurons. However, ketamine did not affect evoked EPSCs or spontaneous inhibitory currents (sIPSCs). Pre-incubation of DR slices with the mTOR inhibitor PP242 decreased the frequency of sEPSCs and prevented the effect of ketamine. The results also show that while no electrophysiological effects were detected 24 h after ketamine administration, phosphorylation levels of mTOR were significantly increased in the DR. Nevertheless, expression levels of synaptic proteins were unaffected at that time. Altogether, the present data demonstrate that ketamine transiently increases spontaneous AMPA receptor-mediated neurotransmission in the DR.

Opioid Activity in the Locus Coeruleus Is Modulated by Chronic Neuropathic Pain.

Pain affects both sensory and emotional aversive responses, often provoking depression and anxiety-related conditions when it becomes chronic. As the opioid receptors in the locus coeruleus (LC) have been implicated in pain, stress responses, and opioid drug effects, we explored the modifications to LC opioid neurotransmission in a chronic constriction injury (CCI) model of short- and long-term neuropathic pain (7 and 30 days after nerve injury). No significant changes were found after short-term CCI, yet after 30 days, CCI provoked an up-regulation of cAMP (cyclic 5'-adenosine monophosphate), pCREB (phosphorylated cAMP response element binding protein), protein kinase A, tyrosine hydroxylase, and electrical activity in the LC, as well as enhanced c-Fos expression. Acute mu opioid receptor desensitization was more intense in these animals, measured as the decline of the peak current caused by [Met5]-enkephalin and the reduction of forskolin-stimulated cAMP produced in response to DAMGO. Sustained morphine treatment did not markedly modify certain LC parameters in CCI-30d animals, such as [Met5]-enkephalin-induced potassium outward currents or burst activity and c-Fos rebound after naloxone precipitation, which may limit the development of some typical opioid drug-related adaptations. However, other phenomena were impaired by long-term CCI, including the reduction in forskolin-stimulated cAMP accumulation by DAMGO after naloxone precipitation in morphine dependent animals. Overall, this study suggests that long-term CCI leads to changes at the LC level that may contribute to the anxiodepressive phenotype that develops in these animals. Furthermore, opioid drugs produce complex adaptations in the LC in this model of chronic neuropathic pain.

The Neuroprotective Effect of Conditioned Medium from Human Adipose-Derived Mesenchymal Stem Cells is Impaired by N-acetyl Cysteine Supplementation.

Oxidative stress is a common feature in neurodegenerative diseases associated with neuroinflammation, and therefore, has been proposed as a key target for novel therapies for these diseases. Recently, adipose-derived stem cell (ASC)-based cell therapy has emerged as a novel strategy for neuroprotection. In this study, we evaluate the therapeutic role of ASC-conditioned medium (ASC-CM) against H2O2-induced neurotoxicity in a new in vitro model of ec23/brain-derived neurotrophic factor (BDNF)-differentiated human SH-SY5Y neuron-like cells (SH-SY5Yd). In the presence of ASC-CM, stressed SH-SY5Yd cells recover normal axonal morphology (with an almost complete absence of H2O2-induced axonal beading), electrophysiological features, and cell viability. This beneficial effect of ASC-CM was associated with its antioxidant capacity and the presence of growth factors, namely, BDNF, glial cell line-derived neurotrophic factor, and transforming growth factor ß1. Moreover, the neuroprotective effect of ASC-CM was very similar to that obtained from treatment with BDNF, an essential factor for SH-SY5Yd cell survival. Importantly, we also found that the addition of the antioxidant agent N-acetyl cysteine to ASC-CM abolished its restorative effect; this was associated with a strong reduction in reactive oxygen species (ROS), in contrast to the moderate decrease in ROS produced by ASC-CM alone. These results suggest that neuronal restorative effect of ASC-CM is associated with not only the release of essential neurotrophic factors, but also the maintenance of an appropriate redox state to preserve neuronal function.

Inactivation of GIRK channels weakens the pre- and postsynaptic inhibitory activity in dorsal raphe neurons.

The serotonergic tone of the dorsal raphe (DR) is regulated by 5-HT1A receptors, which negatively control serotonergic activity via the activation of G protein-coupled inwardly rectifying K+ (GIRK) channels. In addition, DR activity is modulated by local GABAergic transmission, which is believed to play a key role in the development of mood-related disorders. Here, we sought to characterize the role of GIRK2 subunit-containing channels on the basal electrophysiological properties of DR neurons and to investigate whether the presynaptic and postsynaptic activities of 5-HT1A, GABAB, and GABAA receptors are affected by Girk2 gene deletion. Whole-cell patch-clamp recordings in brain slices from GIRK2 knockout mice revealed that the GIRK2 subunit contributes to maintenance of the resting membrane potential and to the membrane input resistance of DR neurons. 5-HT1A and GABAB receptor-mediated postsynaptic currents were almost absent in the mutant mice. Spontaneous and evoked GABAA receptor-mediated transmissions were markedly reduced in GIRK2 KO mice, as the frequency and amplitude of spontaneous IPSCs were reduced, the paired-pulse ratio was increased and GABA-induced whole-cell currents were decreased. Similarly, the pharmacological blockade of GIRK channels with tertiapin-Q prevented the 5-HT1A and GABAB receptor-mediated postsynaptic currents and increased the paired-pulse ratio. Finally, deletion of the Girk2 gene also limited the presynaptic inhibition of GABA release exerted by 5-HT1A and GABAB receptors. These results indicate that the properties and inhibitory activity of DR neurons are highly regulated by GIRK2 subunit-containing channels, introducing GIRK channels as potential candidates for studying the pathophysiology and treatment of affective disorders.

Fast and Efficient Neural Conversion of Human Hematopoietic Cells.

A major challenge in regenerative medicine is the generation of functionally effective target cells to replace or repair damaged tissues. The finding that most somatic cells can be directly converted into cells of another lineage by the expression of specific transcription factors has paved the way to novel applications. Induced neurons (iNs) represent an alternative source of neurons for disease modeling, drug screening, and potentially, for cell replacement therapy. This unit describes methods for the efficient conversion of blood cells into iNs, including protocols to isolate cord blood CD133+ cells, infect them with Sendai virus vectors that express SOX2 and c-MYC, and differentiate the infected cells (PB-MNCs) into mature neurons. A method to reprogram peripheral blood mononuclear cells into iNs is also described. Support protocols describe how to culture rat astrocytes and characterize the electrophysiology of iNs. © 2016 by John Wiley & Sons, Inc.

Deletion of GIRK2 Subunit of GIRK Channels Alters the 5-HT1A Receptor-Mediated Signaling and Results in a Depression-Resistant Behavior.

BACKGROUND: Targeting dorsal raphe 5-HT1A receptors, which are coupled to G-protein inwardly rectifying potassium (GIRK) channels, has revealed their contribution not only to behavioral and functional aspects of depression but also to the clinical response to its treatment. Although GIRK channels containing GIRK2 subunits play an important role controlling excitability of several brain areas, their impact on the dorsal raphe activity is still unknown. Thus, the goal of the present study was to investigate the involvement of GIRK2 subunit-containing GIRK channels in depression-related behaviors and physiology of serotonergic neurotransmission. METHODS: Behavioral, functional, including in vivo extracellular recordings of dorsal raphe neurons, and neurogenesis studies were carried out in wild-type and GIRK2 mutant mice. RESULTS: Deletion of the GIRK2 subunit promoted a depression-resistant phenotype and determined the behavioral response to the antidepressant citalopram without altering hippocampal neurogenesis. In dorsal raphe neurons of GIRK2 knockout mice, and also using GIRK channel blocker tertiapin-Q, the basal firing rate was higher than that obtained in wild-type animals, although no differences were observed in other firing parameters. 5-HT1A receptors were desensitized in GIRK2 knockout mice, as demonstrated by a lower sensitivity of dorsal raphe neurons to the inhibitory effect of the 5-HT1A receptor agonist, 8-OH-DPAT, and the antidepressant citalopram. CONCLUSIONS: Our results indicate that GIRK channels formed by GIRK2 subunits determine depression-related behaviors as well as basal and 5-HT1A receptor-mediated dorsal raphe neuronal activity, becoming alternative therapeutic targets for psychiatric diseases underlying dysfunctional serotonin transmission.

Fast and efficient neural conversion of human hematopoietic cells.

Neurons obtained directly from human somatic cells hold great promise for disease modeling and drug screening. Available protocols rely on overexpression of transcription factors using integrative vectors and are often slow, complex, and inefficient. We report a fast and efficient approach for generating induced neural cells (iNCs) directly from human hematopoietic cells using Sendai virus. Upon SOX2 and c-MYC expression, CD133-positive cord blood cells rapidly adopt a neuroepithelial morphology and exhibit high expansion capacity. Under defined neurogenic culture conditions, they express mature neuronal markers and fire spontaneous action potentials that can be modulated with neurotransmitters. SOX2 and c-MYC are also sufficient to convert peripheral blood mononuclear cells into iNCs. However, the conversion process is less efficient and resulting iNCs have limited expansion capacity and electrophysiological activity upon differentiation. Our study demonstrates rapid and efficient generation of iNCs from hematopoietic cells while underscoring the impact of target cells on conversion efficiency.

Interaction between the 5-HT system and the basal ganglia: functional implication and therapeutic perspective in Parkinson's disease.

The neurotransmitter serotonin (5-HT) has a multifaceted function in the modulation of information processing through the activation of multiple receptor families, including G-protein-coupled receptor subtypes (5-HT1, 5-HT2, 5-HT4-7) and ligand-gated ion channels (5-HT3). The largest population of serotonergic neurons is located in the midbrain, specifically in the raphe nuclei. Although the medial and dorsal raphe nucleus (DRN) share common projecting areas, in the basal ganglia (BG) nuclei serotonergic innervations come mainly from the DRN. The BG are a highly organized network of subcortical nuclei composed of the striatum (caudate and putamen), subthalamic nucleus (STN), internal and external globus pallidus (or entopeduncular nucleus in rodents, GPi/EP and GPe) and substantia nigra (pars compacta, SNc, and pars reticulata, SNr). The BG are part of the cortico-BG-thalamic circuits, which play a role in many functions like motor control, emotion, and cognition and are critically involved in diseases such as Parkinson's disease (PD). This review provides an overview of serotonergic modulation of the BG at the functional level and a discussion of how this interaction may be relevant to treating PD and the motor complications induced by chronic treatment with L-DOPA.

Role of GIRK channels on the noradrenergic transmission in vivo: an electrophysiological and neurochemical study on GIRK2 mutant mice.

Dysfunctional noradrenergic transmission is related to several neuropsychiatric conditions, such as depression. Nowadays, the role of G protein-coupled inwardly rectifying potassium (GIRK)2 subunit containing GIRK channels controlling neuronal intrinsic excitability in vitro is well known. The aim of this study was to investigate the impact of GIRK2 subunit mutation on the central noradrenergic transmission in vivo. For that purpose, single-unit extracellular activity of locus coeruleus (LC) noradrenergic neurons and brain monoamine levels using the HPLC technique were measured in wild-type and GIRK2 mutant mice. Girk2 gene mutation induced significant differences among genotypes regarding burst activity of LC neurons. In fact, the proportion of neurons displaying burst firing was increased in GIRK2 heterozygous mice as compared to that recorded from wild-type mice. Furthermore, this augmentation was even greater in the homozygous genotype. However, neither the basal firing rate nor the coefficient of variation of LC neurons was different among genotypes. Noradrenaline and serotonin basal levels were altered in the dorsal raphe nucleus from GIRK2 heterozygous and homozygous mice, respectively. Furthermore, noradrenaline levels were increased in LC projecting areas such as the hippocampus and amygdale from homozygous mice, although not in the prefrontal cortex. Finally, potency of clonidine and morphine inhibiting LC activity was reduced in GIRK2 mutant mice, although the efficacy remained unchanged. Altogether, the present study supports the role of GIRK2 subunit-containing GIRK channels on the maintenance of tonic noradrenergic activity in vivo. Electric and neurochemical consequences derived from an altered GIRK2-dependent signalling could facilitate the understanding of the neurobiological basis of pathologies related to a dysfunctional monoaminergic transmission.

Pre- and postsynaptic regulation of locus coeruleus neurons after chronic morphine treatment: a study of GIRK-knockout mice.

While the acute inhibitory effect of opioids on locus coeruleus (LC) neurons is mediated primarily by the activation of G protein-gated inwardly-rectifying K(+) (GIRK) channels, the 3'-5'-cyclic adenosine monophosphate (cAMP) system has been implicated in the effects of chronic morphine exposure. Presently, the impact of chronic morphine treatment on GIRK-dependent and GIRK-independent mechanisms underlying the opioid-induced inhibition of LC neurons is unclear. Here, opioid-induced postsynaptic inhibition was studied in LC neurons from wild-type and GIRK2/GIRK3(-/-) mice at baseline and following chronic morphine treatment. The postsynaptic inhibition of LC neurons caused by the opioid agonist [Met](5) enkephalin (ME) was unaffected by chronic morphine treatment in mice of either genotype. Furthermore, chronic morphine treatment had no effect on the forskolin augmentation of the ME-induced current in wild-type LC neurons and only a minor effect on the ME-induced current in LC neurons from GIRK2/GIRK3(-/-) mice. Chronic morphine treatment did, however, lead to an increased frequency of spontaneous excitatory postsynaptic currents (EPSCs) in the LC. Interestingly, while forskolin augmented the EPSC frequency similarly in untreated and morphine-treated wild-type mice, as well as untreated GIRK2/GIRK3(-/-) mice, it failed to increase the frequency of EPSCs in morphine-treated GIRK2/GIRK3(-/-) mice. Altogether, the findings suggest that chronic morphine treatment exerts little impact on ion channels and signaling pathways that mediate the postsynaptic inhibitory effects of opioids but does enhance excitatory neurotransmission in the mouse LC.

Excitatory regulation of noradrenergic neurons by L-arginine/nitric oxide pathway in the rat locus coeruleus in vivo.

To elucidate conflicting findings about the role of L-arginine/nitric oxide (NO) pathway in the locus coeruleus (LC), we investigated the effects of different drugs affecting NO concentrations by single-unit extracellular recordings from LC neurons in vivo and in vitro. In anesthetized rats, central (3.8-15.3 nmol i.c.v.) and local (16.5-66 pmol into the LC) administrations of the NO donor sodium nitroprusside, but not those of the inactive analogue potassium ferricyanide (16.5-66 pmol into the LC), increased by 65-84% the firing rate of LC neurons. In brain slices, low concentrations (50-200 microM) of diethylamine/NO complex, a short-lived NO releaser, also increased the neuron firing rate, although higher drug concentrations (400-800 microM) caused slowly reversible reductions of the firing activity. On the other hand, the NO synthase inhibitors N(omega)-nitro-L-arginine methyl ester (L-NAME) (148-371 nmol i.c.v.) and N(omega)-nitro-L-arginine (L-NA) (46 nmol i.c.v.) gradually decreased the firing rate of LC neurons, whereas the NO synthase substrate L-arginine (0.71-1.42 micromol i.c.v. and 0.6-4.8 nmol into the LC) increased the neuron activity. The latter effect was not mimicked by the vehicle or the less active isomer D-arginine (0.6-4.8 nmol into the LC). Unexpectedly, pretreatment with high concentrations of L-NAME (371 nmol and 18.5 micromol i.c.v.) or L-NA (45.6 nmol i.c.v. and 0.24 nmol into the LC) failed to block the effect of L-arginine. The glutamate receptor antagonist kynurenic acid (1 micromol i.c.v.) strongly reduced the effect of L-arginine but not that of sodium nitroprusside. These data confirm in vivo a direct excitatory effect of NO on LC neurons and suggest a tonic regulation of noradrenergic neurons by NO in vivo. L-arginine also excites LC neurons, but this effect may be caused by a nitric-oxide-unrelated glutamate-receptor-mediated mechanism.