Mitral valve-in-valve implantation: A case report.

INTRODUCTION: Mitral valve-in-valve implantation is a new therapeutic tool in the field of structural interventional cardiology for patients with bioprosthetic dysfunction due to severe mitral valve regurgitation and high surgical risk. The objective was to develop an individualised nursing care plan for a patient undergoing this procedure; the first case in our centre. CASE DESCRIPTION: A 75-year-old woman, independent for activities of daily living, with a history of chronic renal failure and biological mitral valve replacement due to rheumatic valve disease. She was admitted to the acute cardiac care unit for severe symptomatic mitral valve regurgitations secondary to mitral bioprosthesis dysfunction. Heart surgery was ruled out due to comorbidities and high surgical risk, and the patient underwent percutaneous mitral valve-in-valve implantation. The implantation was successful. ASSESSMENT: The nursing assessment followed Marjory Gordon's conceptual model identifying the following impaired patterns: pattern 2: bilateral malleolar oedema without pitting; pattern 3: urinary catheter and intravenous diuretic use; pattern 4: dyspnoea on moderate exertion, dry nocturnal cough, orthopnoea and respiratory disturbances, and activity intolerance; pattern 5: need for pharmacological assistance for a good night's rest. DIAGNOSES: The following nursing diagnoses were established using the NANDA taxonomy: Excess fluid volume; ineffective breathing pattern; Activity intolerance and problem collaborating: Hypotension and anaemia secondary to deep thigh haematoma. PLANNING: The following objectives were set based on the NOC taxonomy: Fluid balance; Respiratory status: ventilation; Cardiopulmonary status and the following NIC interventions: Hypervolaemia management; Respiratory monitoring and oxygen therapy; Vital sign monitoring and heart care. DISCUSSION: Nursing interventions aimed at monitoring haemodynamic status, fluid restriction together with the efficacy of diuretic treatment achieved a negative water balance which contributed to fluid depletion improving respiratory symptoms, enabling implantation under better conditions. CONCLUSIONS: Technological progress in the health sciences, and in the field of acute cardiology in particular, directly calls for training, revision and updating of critical care nursing. Given this dynamic and continually evolving process, the specialist intensive care nurse, the inclusion of the cardiovascular nurse specialist in multidisciplinary teams such as the heart team, and expanding the consultation of the haemodynamic nurse are urgently required to ensure optimal nursing care, safety, and care quality.

Valve in valve mitral: a propósito de un caso / Mitral valve-in-valve implantation: A case report

Introducción: El implante valve in valve mitral es una nueva herramienta terapéutica que ha surgido recientemente en el campo del intervencionismo estructural en cardiología para pacientes con disfunción bioprotésica por insuficiencia mitral severa y alto riesgo quirúrgico. El objetivo es elaborar un plan de cuidados enfermero individualizado destinado a una paciente que se somete a este procedimiento, siendo el primer caso en nuestro centro. Descripción del caso: Mujer de 75años, independiente para las actividades de la vida diaria, con antecedentes de insuficiencia renal crónica y recambio valvular mitral biológico por valvulopatía reumática. Ingresada en la unidad de cuidados cardiológicos agudos por insuficiencia mitral severa sintomática secundaria a disfunción de la bioprótesis mitral. Descartada para cirugía cardíaca por comorbilidades y alto riesgo quirúrgico, se procedió al valve in valve mitral percutáneo, siendo exitoso su implante. Valoración: La valoración enfermera se realizó siguiendo el modelo conceptual de Marjory Gordon, donde se identificaron los siguientes patrones alterados: patrón2: edemas maleolares bilaterales sin fovea; patrón3: sondaje vesical y uso de diurético intravenoso; patrón4: disnea a moderados esfuerzos, tos seca nocturna, ortopnea y alteraciones respiratorias e intolerancia a la actividad; patrón5: necesidad de ayuda farmacológica para el buen descanso nocturno. Diagnósticos: Mediante la taxonomía NANDA se establecieron los diagnósticos enfermeros: Exceso de volumen de líquidos; Patrón respiratorio ineficaz; Intolerancia a la actividad y el problema de colaboración: Hipotensión y anemización secundaria al hematoma profundo en muslo.(AU)

Introduction: Mitral valve-in-valve implantation is a new therapeutic tool in the field of structural interventional cardiology for patients with bioprosthetic dysfunction due to severe mitral valve regurgitation and high surgical risk. The objective was to develop an individualised nursing care plan for a patient undergoing this procedure; the first case in our centre. Case description: A 75-year-old woman, independent for activities of daily living, with a history of chronic renal failure and biological mitral valve replacement due to rheumatic valve disease. She was admitted to the acute cardiac care unit for severe symptomatic mitral valve regurgitations secondary to mitral bioprosthesis dysfunction. Heart surgery was ruled out due to comorbidities and high surgical risk, and the patient underwent percutaneous mitral valve-in-valve implantation. The implantation was successful. Assessment: The nursing assessment followed Marjory Gordon's conceptual model identifying the following impaired patterns: pattern2: bilateral malleolar oedema without pitting; pattern3: urinary catheter and intravenous diuretic use; pattern4: dyspnoea on moderate exertion, dry nocturnal cough, orthopnoea and respiratory disturbances, and activity intolerance; pattern5: need for pharmacological assistance for a good night's rest.Diagnoses: The following nursing diagnoses were established using the NANDA taxonomy: Excess fluid volume; Ineffective breathing pattern; Activity intolerance and problem collaborating; Hypotension and anaemia secondary to deep thigh haematoma.(AU)

Deficits in coordinated neuronal activity and network topology are striatal hallmarks in Huntington's disease.

BACKGROUND: Network alterations underlying neurodegenerative diseases often precede symptoms and functional deficits. Thus, their early identification is central for improved prognosis. In Huntington's disease (HD), the cortico-striatal networks, involved in motor function processing, are the most compromised neural substrate. However, whether the network alterations are intrinsic of the striatum or the cortex is not fully understood. RESULTS: In order to identify early HD neural deficits, we characterized neuronal ensemble calcium activity and network topology of HD striatal and cortical cultures. We used large-scale calcium imaging combined with activity-based network inference analysis. We extracted collective activity events and inferred the topology of the neuronal network in cortical and striatal primary cultures from wild-type and R6/1 mouse model of HD. Striatal, but not cortical, HD networks displayed lower activity and a lessened ability to integrate information. GABAA receptor blockade in healthy and HD striatal cultures generated similar coordinated ensemble activity and network topology, highlighting that the excitatory component of striatal system is spared in HD. Conversely, NMDA receptor activation increased individual neuronal activity while coordinated activity became highly variable and undefined. Interestingly, by boosting NMDA activity, we rectified striatal HD network alterations. CONCLUSIONS: Overall, our integrative approach highlights striatal defective network integration capacity as a major contributor of basal ganglia dysfunction in HD and suggests that increased excitatory drive may serve as a potential intervention. In addition, our work provides a valuable tool to evaluate in vitro network recovery after treatment intervention in basal ganglia disorders.

Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) Enhances Hippocampal Synaptic Plasticity and Improves Memory Performance in Huntington's Disease.

Deficits in hippocampal synaptic plasticity result in cognitive impairment in Huntington's disease (HD). Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide that exerts neuroprotective actions, mainly through the PAC1 receptor. However, the role of PACAP in cognition is poorly understood, and no data exists in the context of Huntington's disease (HD). Here, we investigated the ability of PACAP receptor stimulation to enhance memory development in HD. First, we observed a hippocampal decline of all three PACAP receptor expressions, i.e., PAC1, VPAC1, and VPAC2, in two different HD mouse models, R6/1 and HdhQ7/Q111, from the onset of cognitive dysfunction. In hippocampal post-mortem human samples, we found a specific decrease of PAC1, without changes in VPAC1 and VPAC2 receptors. To determine whether activation of PACAP receptors could contribute to improve memory performance, we conducted daily intranasal administration of PACAP38 to R6/1 mice at the onset of cognitive impairment for seven days. We found that PACAP treatment rescued PAC1 level in R6/1 mice, promoted expression of the hippocampal brain-derived neurotrophic factor, and reduced the formation of mutant huntingtin aggregates. Furthermore, PACAP administration counteracted R6/1 mice memory deficits as analyzed by the novel object recognition test and the T-maze spontaneous alternation task. Importantly, the effect of PACAP on cognitive performance was associated with an increase of VGlut-1 and PSD95 immunolabeling in hippocampus of R6/1 mice. Taken together, these results suggest that PACAP, acting through stimulation of PAC1 receptor, may have a therapeutic potential to counteract cognitive deficits induced in HD.

Genetic features of human and bovine Escherichia coli O157:H7 strains isolated in Argentina.

Shiga toxin-producing Escherichia coli (STEC) are important food-borne pathogens associated with human diseases. In Argentina, O157:H7 is the dominant serotype in hemolytic uremic syndrome (HUS) cases. Previously, we have described the almost exclusive circulation of human E. coli O157 strains belonging to the hypervirulent clade 8 in Neuquén Province. The aim of the present study was to investigate, by a broad molecular characterization, if this particular distribution of E. coli O157 clades in Neuquén is similar to the situation in other regions of the country and if it may be originated in a similar profile in cattle, its main reservoir. Two-hundred and eighty O157 strains (54 bovine and 226 human) isolated between 2006 and 2008 in different regions of Argentina were studied. All strains harbored rfbO157, fliCH7, eae, and ehxA genes. The predominant genotype was stx2a/stx2c in human (76.1%) and bovine (55.5%) strains. All human isolates tested by Lineage-Specific Polymorphism Assay (LSPA-6), were lineage I/II; among bovine strains, 94.1% belonged to lineage I/II and 5.9% to lineage I. No LSPA-6 lineage II isolates were detected. Single nucleotide polymorphism (SNP) analysis has revealed the existence of nine clade phylogenetic groups. In our clinical strains collection, 87.6% belonged to the hypervirulent clade 8, and 12.4% were classified as clade 4/5. In bovine isolates, 59.3% strains were clade 8, 33.3% clade 4/5 and 7.4% clade 3. More than 80% of human strains showed the presence of 6 of the 7 virulence determinants described in the TW14359 O157 strain associated with the raw spinach outbreak in the U.S. in 2006. More than 80% of bovine strains showed the presence of 3 of these factors. The q933 allele, which has been related to high toxin production, was present in 98.2% of clinical strains and 75.9% of the bovine isolates. The molecular characterization of human STEC O157 strains allows us to conclude that the particular situation previously described for Neuquén Province, may actually be a characteristic of the whole country. These genetic features are quite similar to those observed in the bovine reservoir and may be derived from it. This data confirms that, unlike the rest of the world, in Argentina most of the STEC O157 strains present in cattle may cause human infections of varying severity and the marked virulence described for these strains may be related to the high incidence of HUS in our country.

SLC6A15, a novel stress vulnerability candidate, modulates anxiety and depressive-like behavior: involvement of the glutamatergic system.

Major depression is a multifactorial disease, involving both environmental and genetic risk factors. Recently, SLC6A15 - a neutral amino acid transporter mainly expressed in neurons - was proposed as a new candidate gene for major depression and stress vulnerability. Risk allele carriers for a single nucleotide polymorphism (SNP) in a SLC6A15 regulatory region display altered hippocampal volume, glutamate levels, and hypothalamus-pituitary-adrenal axis activity, all markers associated with major depression. Despite this genetic link between SLC6A15 and depression, its functional role with regard to the development and maintenance of depressive disorder is still unclear. The aim of the current study was therefore to characterize the role of mouse slc6a15 in modulating brain function and behavior, especially in relation to stress as a key risk factor for the development of mood disorders. We investigated the effects of slc6a15 manipulation using two mouse models, a conventional slc6a15 knock-out mouse line (SLC-KO) and a virus-mediated hippocampal slc6a15 overexpression (SLC-OE) model. Mice were tested under basal conditions and following chronic social stress. We found that SLC-KO animals displayed a similar behavioral profile to wild-type littermates (SLC-WT) under basal conditions. Interestingly, following chronic social stress SLC-KO animals showed lower levels of anxiety- and depressive-like behavior compared to stressed WT littermates. In support of these findings, SLC-OE animals displayed increased anxiety-like behavior already under basal condition. We also provide evidence that GluR1 expression in the dentate gyrus, but not GluR2 or NR1, are regulated by slc6a15 expression, and may contribute to the difference in stress responsiveness observed between SLC-KO and SLC-WT animals. Taken together, our data demonstrate that slc6a15 plays a role in modulating emotional behavior, possibly mediated by its impact on glutamatergic neurotransmission.

Deciphering the spatio-temporal expression and stress regulation of Fam107B, the paralog of the resilience-promoting protein DRR1 in the mouse brain.

Understanding the molecular mechanisms that promote stress resilience might open up new therapeutic avenues to prevent stress-related disorders. We recently characterized a stress and glucocorticoid-regulated gene, down-regulated in renal cell carcinoma - DRR1 (Fam107A). DRR1 is expressed in the mouse brain; it is up-regulated by stress and glucocorticoids and modulates neuronal actin dynamics. In the adult mouse, DRR1 was shown to facilitate specific behaviors which might be protective against some of the deleterious consequences of stress exposure: in the hippocampal CA3 region, DRR1 improved cognitive performance whereas in the septum, it specifically increased social behavior. Therefore DRR1 was suggested as a candidate protein promoting stress-resilience. Fam107B (family with sequence similarity 107, member B) is the unique paralog of DRR1, and both share high sequence similarities, predicted glucocorticoid response elements, heat-shock induction and tumor suppressor properties. So far, the role of Fam107B in the central nervous system was not studied. The aim of the present investigation, therefore, was to analyze whether Fam107B and DRR1 display comparable mRNA expression patterns in the brain and whether both are modulated by stress and glucocorticoids. Spatio-temporal mapping of Fam107B mRNA expression in the embryonic and adult mouse brain, by means of in situ hybridization, showed that Fam107B was expressed during embryogenesis and in the adulthood, with particularly high and specific expression in the forming telencephalon suggestive of an involvement in corticogenesis. In the adult mouse, expression was restricted to neurogenic niches, like the dentate gyrus. In contrast to DRR1, Fam107B mRNA expression failed to be modulated by glucocorticoids and social stress in the adult mouse. In summary, Fam107B and DRR1 show different spatio-temporal expression patterns in the central nervous system, suggesting at least partially different functional roles in the brain, and where the glucocorticoid receptor (GR)-induced regulation appears to be a unique property of DRR1.

RNAi-mediated serotonin transporter suppression rapidly increases serotonergic neurotransmission and hippocampal neurogenesis.

Current antidepressants, which inhibit the serotonin transporter (SERT), display limited efficacy and slow onset of action. Here, we show that partial reduction of SERT expression by small interference RNA (SERT-siRNA) decreased immobility in the tail suspension test, displaying an antidepressant potential. Moreover, short-term SERT-siRNA treatment modified mouse brain variables considered to be key markers of antidepressant action: reduced expression and function of 5-HT(1A)-autoreceptors, elevated extracellular serotonin in forebrain and increased neurogenesis and expression of plasticity-related genes (BDNF, VEGF, Arc) in hippocampus. Remarkably, these effects occurred much earlier and were of greater magnitude than those evoked by long-term fluoxetine treatment. These findings highlight the critical role of SERT in serotonergic function and show that the reduction of SERT expression regulates serotonergic neurotransmission more potently than pharmacological blockade of SERT. The use of siRNA-targeting genes in serotonin neurons (SERT, 5-HT(1A)-autoreceptor) may be a novel therapeutic strategy to develop fast-acting antidepressants.

Genotypic characterization of non-O157 Shiga toxin-producing Escherichia coli in beef abattoirs of Argentina.

The non-O157 Shiga toxin-producing Escherichia coli (STEC) contamination in carcasses and feces of 811 bovines in nine beef abattoirs from Argentina was analyzed during a period of 17 months. The feces of 181 (22.3%) bovines were positive for non-O157 STEC, while 73 (9.0%) of the carcasses showed non-O157 STEC contamination. Non-O157 STEC strains isolated from feces (227) and carcasses (80) were characterized. The main serotypes identified were O178:H19, O8:H19, O130:H11, and O113:H21, all of which have produced sporadic cases of hemolytic-uremic syndrome in Argentina and worldwide. Twenty-two (7.2%) strains carried a fully virulent stx/eae/ehxA genotype. Among them, strains of serotypes O103:[H2], O145:NM, and O111:NM represented 4.8% of the isolates. Xba I pulsed-field gel electrophoresis pattern analysis showed 234 different patterns, with 76 strains grouped in 30 clusters. Nine of the clusters grouped strains isolated from feces and from carcasses of the same or different bovines in a lot, while three clusters were comprised of strains distributed in more than one abattoir. Patterns AREXSX01.0157, AREXBX01.0015, and AREXPX01.0013 were identified as 100% compatible with the patterns of one strain isolated from a hemolytic-uremic syndrome case and two strains previously isolated from beef medallions, included in the Argentine PulseNet Database. In this survey, 4.8% (39 of 811) of the bovine carcasses appeared to be contaminated with nonO157 STEC strains potentially capable of producing sporadic human disease, and a lower proportion (0.25%) with strains able to produce outbreaks of severe disease.

Resultados de la punción aspiración con aguja fina y la biopsia por punción con estudio anatomopatológico definitivo en lesiones mamarias / No disponible

Objetivo: Valorar los resultados de la punción aspiración con aguja fina (PAAF) y la biopsia por punción (BPP) de lesiones mamarias con estudio anatomopatológico de la pieza quirúrgica. Pacientes y métodos: Estudio retrospectivo y observacional de 144 pacientes durante dos años con PAAF, BPP y pieza quirúrgica. Resultados: Del total de 144 lesiones el diagnóstico anatomopatológico fue: 17 de benigno, 10 de hiperplasia, 7 de carcinomas in situ, 108 de carcinoma y 2 otros. En 2 de los 17 casos benignos la PAAF y la BPP diagnosticaron un carcinoma. Eran casos sometidos a quimioterapia neoadyuvante con respuesta total. En otro caso de hiperplasia por PAAF y carcinoma por BPP, la lesión se extirpó en su totalidad con esta técnica. De los 108 carcinomas, 10 casos fueron falsos negativos por BPP. En 8 el diagnóstico fue benigno y en 2 de hiperplasia. En 4 casos la PAAF indicó un carcinoma, en 2 fue sospechosa, 1 benigna y en otra no se obtuvo material celular. En la PAAF se detectaron 3 falsos negativos. En 2 de ellos la BPP diagnosticó carcinoma y en otro benignidad. El caso que fue diagnosticado de benigno por ambas técnicas era un carcinoma en glándula mamaria axilar. Conclusión: En el estudio hay un número bajo de lesiones benignas controladas por imagen y de hiperplasias y carcinomas in situ al no tener citología por presentarse con microcalcificaciones. En la casuística analizada, la PAAF y la BPP son técnicas complementarias para el diagnóstico de lesiones mamarias(AU)

Objective: To evaluate the results of fine needle aspiration (FNA) and core biopsy (CB) of breast lesions with pathologic diagnosis. Patients and methods: A retrospective, observational study of 144 patients in two years with FNA, CB and surgical specimen. Results: Pathological diagnosis of the 144 lesions were: 17 benign, 10 hyperplasia, 7 carcinoma in situ, 108 carcinoma and 2 others. In 2 of 17 benign cases, FNA and CB diagnosed carcinoma. These cases were treated with neoadjuvant chemotherapy with a complete response. In other case of hyperplasia in FNA and carcinoma in CB was totally excised by this technique. Ten of the 108 carcinomas were false negatives in CB (8 benign, 2 hyperplasia). In 4 cases FNA diagnosed carcinoma, 2 were suspicious of malignancy, 1 benign and in other there was no material for a diagnosis. In FNA there were 3 false negatives, 2 of them were diagnosed of carcinoma and benign by CB. The case diagnosed of benign by both techniques was a carcinoma arising in a mammary axillary gland. Conclusion: In this study the number of benign lesions is low because they were followed by image techniques. Also there are few hyperplasias and carcinomas in situ which are diagnosed by mammography for microcalcifications and they do not have cytological study. In the cases studied, FNA and CB are complementary techniques for the diagnosis of breast lesions(AU)

Prevalence, characterization, and genotypic analysis of Escherichia coli O157:H7/NM from selected beef exporting abattoirs of Argentina.

In Argentina, Escherichia coli O157:H7/NM (STEC O157) is the prevalent serotype associated with hemolytic uremic syndrome (HUS), which is endemic in the country with more than 400 cases per year. In order to estimate the prevalence and characteristics of STEC O157 in beef cattle at slaughter, a survey of 1,622 fecal and carcass samples was conducted in nine beef exporting abattoirs from November 2006 to April 2008. A total of 54 samples were found positive for STEC O157, with an average prevalence of 4.1% in fecal content and 2.6% in carcasses. Calves and heifers presented higher percentages of prevalence in feces, 10.5 and 8.5%, respectively. All STEC O157 isolates harbored stx(2) (Shiga toxin 2), eae (intimin), ehxA (enterohemolysin), and fliC(H7) (H7 flagellin) genes, while stx(1) (Shiga toxin 1) was present in 16.7% of the strains. The prevalent (56%) stx genotype identified was stx(2) combined with variant stx(2c (vh-a)), the combination of which is also prevalent (>90%) in STEC O157 post-enteric HUS cases in Argentina. The clonal relatedness of STEC O157 strains was established by phage typing and pulsed-field gel electrophoresis (PFGE). The 54 STEC isolates were categorized into 12 different phage types and in 29 XbaI-PFGE patterns distributed in 27 different lots. STEC O157 strains isolated from 5 of 21 carcasses were identical by PFGE (100% similarity) to strains of the fecal content of the same or a contiguous bovine in the lot. Five phage type-PFGE-stx profiles of 10 strains isolated in this study matched with the profiles of the strains recovered from 18 of 122 HUS cases that occurred in the same period.

Trichothecenes and mycoflora in wheat harvested in nine locations in Buenos Aires province, Argentina.

A total of 120 freshly harvested wheat samples from the 2004 season in nine locations from Northern Buenos Aires Province, Argentina, were analysed for trichothecene natural occurrence and associated mycoflora, and for determining the influence of commonly used fungicide field treatment and the cultivar type on trichothecene contamination. The trichothecenes T-2 tetraol, T-2 triol, HT-2 and T-2 toxin (HT-2, T-2), diacetoxyscirpenol (DAS), nivalenol (NIV), deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-ADON) and 15-acetyldeoxynivalenol (15-ADON) were analysed by gas chromatography and electron capture detection. Detection limits ranged from 4 to 20 microg/kg. The isolation frequencies of species were calculated. Alternaria alternata, Fusarium graminearum, Fusarium poae and Fusarium semitectum were the predominant fungal species identified as endogenous mycoflora. The type of cultivar and the fungicide field treatment did not affect significantly the trichothecene contamination. The trichothecenes type A detected were HT-2 and T-2 triol toxins and the type B were DON, NIV and 3-ADON. Based on 120 samples the incidences were 21.7% for 3-ADON, 22.5% for HT-2, 27.5% for T-2 triol and 85% for DON. NIV was confirmed in one sample. Mean levels of trichothecene positive samples were between 7 and 2788 microg/kg.

Effect of MT1 melatonin receptor deletion on melatonin-mediated phase shift of circadian rhythms in the C57BL/6 mouse.

In the mouse suprachiasmatic nucleus (SCN), melatonin activates MT1 and MT2 G-protein coupled receptors, which are involved primarily in inhibition of neuronal firing and phase shift of circadian rhythms. This study investigated the ability of melatonin to phase shift circadian rhythms in wild type (WT) and MT1 melatonin receptor knockout (KO) C57BL/6 mice. In WT mice, melatonin (90 microg/mouse, s.c.) administered at circadian time 10 (CT10; CT12 onset of activity) significantly phase advanced the onset of the circadian activity rhythm (0.60 +/- 0.09 hr, n = 41) when compared with vehicle treated controls (-0.02 +/- 0.07 hr, n = 28) (P < 0.001). In contrast, C57 MT1KO mice treated with melatonin did not phase shift circadian activity rhythms (-0.10 +/- 0.12 hr, n = 42) when compared with vehicle treated mice (-0.12 +/- 0.07 hr, n = 43). Similarly, in the C57 MT1KO mouse melatonin did not accelerate re-entrainment to a new dark onset after an abrupt advance of the dark cycle. In contrast, melatonin (3 and 10 pm) significantly phase advanced circadian rhythm of neuronal firing in SCN brain slices independent of genotype with an identical maximal shift at 10 pm (C57 WT: 3.61 +/- 0.38 hr, n = 3; C57 MT(1)KO: 3.45 +/- 0.11 hr, n = 4). Taken together, these results suggest that melatonin-mediated phase advances of circadian rhythms of neuronal firing in the SCN in vitro may involve activation of the MT2 receptor while in vivo activation of the MT1 and possibly the MT2 receptor may be necessary for the expression of melatonin-mediated phase shifts of overt circadian activity rhythms.

The antidepressant-like effect of the melatonin receptor ligand luzindole in mice during forced swimming requires expression of MT2 but not MT1 melatonin receptors.

We previously reported an antidepressant-like effect in C3H/HeN mice during the forced swimming test (FST) following treatment with the MT1/MT2 melatonin receptor ligand, luzindole. This study investigated the role melatonin receptors (MT1 and/or MT2) may play in the effect of luzindole in the FST using C3H/HeN mice with a genetic deletion of either MT1 (MT1KO) or MT2 (MT2KO) melatonin receptors. In the light phase (ZT 9-11), luzindole (30 mg/kg, i.p.) significantly decreased immobility during swimming in both wild type (WT) (135.6 +/- 25.3 s, n = 7) and MT(1)KO (132.6 +/- 13.3 s, n = 8) as compared with vehicle-treated mice (WT: 207.1 +/- 6.0 s, n = 7; MT1KO: 209.5 +/- 6.2 s, n = 8) (P < 0.001). In the dark phase (ZT 20-22), luzindole also decreased time of immobility in both WT (89.5 +/- 13.9 s, n = 8) and MT1KO (66.5 +/- 6.4 s, n = 8) mice as compared with the vehicle treated (WT: 193.8 +/- 3.5, n = 6; MT1KO: 176.6 +/- 6.2 s, n = 8) (P < 0.001). Genetic disruption of the MT1 gene did not alter the diurnal rhythm of serum melatonin in MT1KO mice (ZT 9-11: 1.3 +/- 0.6 pg/mL, n = 7; ZT 20-22: 10.3 +/- 1.1 pg/mL, n = 8) as compared with WT (ZT 9-11: 1.4 +/- 0.7 pg/mL; ZT 20-22: 10.6 pg/mL). Swimming did not alter the serum melatonin diurnal rhythm in WT and MT1KO mice. Decreases in immobility of WT and MT1KO mice by luzindole treatment were not affected by gender or age (3 months versus 8 months). In contrast, luzindole did not decrease immobility during the FST in MT2KO mice. We conclude that the antidepressant-like effect of luzindole may be mediated through blockade of MT2 rather than MT1 melatonin receptors.

Short-term exposure to melatonin differentially affects the functional sensitivity and trafficking of the hMT1 and hMT2 melatonin receptors.

The hormone melatonin mediates a variety of physiological functions in mammals through activation of pharmacologically distinct MT(1) and MT(2) G protein-coupled melatonin receptors. We therefore sought to investigate how the receptors were regulated in response to short melatonin exposure. Using 2-[(125)I]iodomelatonin binding, cAMP functional assays, and confocal microscopy, we demonstrated robust differences in specific 2-[(125)I]iodomelatonin binding, receptor desensitization, and cellular trafficking of hMT(1) and hMT(2) melatonin receptors expressed in Chinese hamster ovary (CHO) cells after short (10-min) exposure to melatonin. Exposure to melatonin decreased specific 2-[(125)I]iodomelatonin binding to CHO-MT(2) cells (70.3 +/- 7.6%, n = 3) compared with vehicle controls. The robust decreases in specific binding to the hMT(2) melatonin receptors correlated both with the observed functional desensitization of melatonin to inhibit forskolin-stimulated cAMP formation in CHO-MT(2) cells pretreated with 10 nM melatonin (EC(50) of 159.8 +/- 17.8 nM, n = 3, p < 0.05) versus vehicle (EC(50) of 6.0 +/- 1.2 nM, n = 3), and with the arrestin-dependent internalization of the receptor. In contrast, short exposure of CHO-MT(1) cells to melatonin induced a small decrease in specific 2-[(125)I]iodomelatonin binding (34.2 +/- 13.0%, n = 5) without either desensitization or receptor internalization. We conclude that differential regulation of the hMT(1) and hMT(2) melatonin receptors by the hormone melatonin could underlie temporally regulated signal transduction events mediated by the hormone in vivo.

Melatonin receptor signaling: finding the path through the dark.

Melatonin, dubbed "the hormone of darkness," is involved in relaying photoperiodic information to the organism. Not only is melatonin involved in the regulation of circadian rhythms and sleep, but it also has roles in visual, cerebrovascular, reproductive, neuroendocrine, and neuroimmunological functions. Melatonin mediates its effects through G protein-coupled receptors: MT(1), MT(2), and, possibly, MT(3). Pharmacological agents have been instrumental in identifying these receptor types. Masana and Dubocovich discuss how the level of receptor expression may alter their efficacy, so that caution is necessary when extrapolating the pharmacological properties of ligands defined on recombinant systems to the receptors in the organism. With these cautions in mind, they describe the various signaling pathways and physiological roles ascribed to the three melatonin receptor types.

Circadian rhythm of mt1 melatonin receptor expression in the suprachiasmatic nucleus of the C3H/HeN mouse.

This report studied the diurnal and circadian rhythms of mt1 melatonin receptor expression in the SCN of C3H/HeN mice maintained in either a light:dark (LD) cycle or in constant dark for a minimum of 6 wk. Diurnal times (ZT) were assessed with reference to the onset of the light period (ZT0) and circadian times (CT) were established by determining the phase of wheel running activity of each mouse before sacrifice. 2-[125I]-Iodomelatonin binding in the SCN revealed low amplitude diurnal and circadian rhythms with highest levels of binding 2 hr after lights on (41.3+/-1.7 fmol/mg protein, n = 5, at ZT2) or at the beginning of the subjective day (48.6+/-2.1 fmol/mg protein, n = 6, CT2), respectively. The expression of mt1 mRNA, determined by in situ hybridization with a 35S-labeled mouse mt1 riboprobe, showed robust diurnal and circadian rhythms. In animals housed under a LD cycle, low levels of expression were observed during the day, with a rapid rise in mt1 melatonin receptor expression at the beginning of the dark period (ZT14), coincident with an abrupt increase in levels of circulating melatonin measured by radioimmunoassay. In animals housed under constant dark conditions, a robust peak of mt1 mRNA expression occurred in the middle of the subjective night (CT18), 8 hr before the peak of protein expression, while the lowest levels of mt1 mRNA expression were observed during the day (CTI10). Results suggest that mt1 melatonin receptor rhythm in the C3H/HeN mouse SCN is regulated both by light and by the biological clock as distinct rhythms of both mRNA and protein are differentially expressed under a LD cycle and constant dark conditions.

Lithium regulates PKC-mediated intracellular cross-talk and gene expression in the CNS in vivo.

It has become increasingly appreciated that the long-term treatment of complex neuropsychiatric disorders like bipolar disorder (BD) involves the strategic regulation of signaling pathways and gene expression in critical neuronal circuits. Accumulating evidence from our laboratories and others has identified the family of protein kinase C (PKC) isozymes as a shared target in the brain for the long-term action of both lithium and valproate (VPA) in the treatment of BD. In rats chronically treated with lithium at therapeutic levels, there is a reduction in the levels of frontal cortical and hippocampal membrane-associated PKC alpha and PKC epsilon. Using in vivO microdialysis, we have investigated the effects of chronic lithium on the intracellular cross-talk between PKC and the cyclic AMP (cAMP) generating system in vivo. We have found that activation of PKC produces an increase in dialysate cAMP levels in both prefrontal cortex and hippocampus, effects which are attenuated by chronic lithium administration. Lithium also regulates the activity of another major signaling pathway the c-Jun N-terminal kinase pathway--in a PKC-dependent manner. Both Li and VPA, at therapeutically relevant concentrations, increase the DNA binding of activator protein 1 (AP-1) family of transcription factors in cultured cells in vitro, and in rat brain ex vivo. Furthermore, both agents increase the expression of an AP-1 driven reporter gene, as well as the expression of several endogenous genes known to be regulated by AP-1. Together, these results suggest that the PKC signaling pathway and PKC-mediated gene expression may be important mediators of lithium's long-term therapeutic effects in a disorder as complex as BD.