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Actualmente el Área Natural El Balsamar (en proceso declaratorio) no cuenta con un plan de manejo o un diagnóstico reciente que permita determinar el estado actual de las comunidades biológicas del área. Por tal razón, a través de una Evaluación Ecológica Rápida (EER), se analizó el estado actual de especies de Anfibios y reptiles; Aves; Mamíferos y Estratos vegetales. Los resultados brindaron información biológica de gran importancia, actualizada y que podrá utilizarse como un insumo técnico científico que dé mayor peso y sustento biológico al proceso declaratorio de Área Natural Protegida por parte del Ministerio de Medio Ambiente y Recursos Naturales (MARN). El registro y levantamiento de información en campo se hizo con metodologías propias para cada taxón o grupo biológico. Se realizó un esfuerzo de muestreo que comprendió tres viajes de campo, durante los meses de septiembre y octubre del presente año. Cada viaje comprendió dos noches y tres días para un total de 9 días de trabajo en campo. Se identificaron 19 especies y 18 familias de anfibios y reptiles, dos reptiles y un anfibio en categoría de Amenaza; 56 especies de aves dentro de 26 familias, que representaron el 10.10% de las especies registradas en el país, dos especies de aves en categoría de Amenaza y una En Peligro. Además, 14 especies de mamíferos terrestres y 8 especies de quirópteros, pertenecientes a 12 familias; 25 especies de árboles con un volumen maderable de 1138.67 m3, 28 arbustivas y 87 especies herbáceas.

Climate change has led to the search for strategies to acclimatize plants to various abiotic stressors to ensure the production and quality of crops of commercial interest. Sorghum is the fifth most important cereal crop, providing several uses including human food, animal feed, bioenergy, or industrial applications. The crop has an excellent adaptation potential to different types of abiotic stresses, such as drought, high salinity, and high temperatures. However, it is susceptible to low temperatures compared with other monocotyledonous species. Here, we have reviewed and discussed some of the research results and advances that focused on the physiological, metabolic, and molecular mechanisms that determine sorghum cold tolerance to improve our understanding of the nature of such trait. Questions and opportunities for a comprehensive approach to clarify sorghum cold tolerance or susceptibility are also discussed.

La siguiente investigación tuvo como fin diseñar un sistema de gestión de inventarios para el almacén Técnitaller S.A.S de la ciudad de Neiva; esto debido a la ineficiente administración de sus inventarios los cuales han generado reprocesos, faltantes, obsolescencia, bajo de nivel de servicio, daño en mercancías entre otros; la metodología empleada corresponde a un estudio no experimental- transversal y descriptivo que inicia con el diagnóstico del área, la elaboración de la propuesta de gestión de inventarios y el análisis económico de la misma; como resultado del análisis se determinó que el modelo a implementar en la empresa integra un sistema de información que comprende 4 módulos de gestión (Compras, almacén, inventarios y despacho), cuyo valor de implementación es de $21.595 150 el cual será realizado por Word Office. La implementación de este sistema permitirá a la empresa optimizar la gestión de inventarios la cual se verá reflejada en unos menores costos de mantener el inventario, de pedir, de almacenar entre otras variables.

El objetivo de la investigación fue determinar la resistividad eléctrica de la madera de Pinus pseudostrobus, Tabebuia rosea y Quercus scytophylla en las direcciones de anisotropía. Para ello, se prepararon 20 probetas de madera sólida de cada una de las especies con dimensiones de 20 mm × 20 mm × 20 mm en las direcciones radial, tangencial y longitudinal, respectivamente, y se determinó la densidad y el contenido de humedad de la madera. Para realizar las pruebas de resistividad eléctrica se midió la resistencia eléctrica empleando corriente continua con una tensión de prueba de 1000 voltios. El contenido de humedad fue para P. pseudostrobus 12,6 %, para T. rosea 10,6 % y para Q. scytophylla 15,6 %. La resistividad eléctrica transversal promedio fue para P. pseudostrobus 45,5 MΩ m, para T. rosea 10,3 MΩ m y para Q. scytophylla 61,4 MΩ m. La resistividad eléctrica longitudinal fue para P. pseudostrobus 24,7 MΩ m, para T. rosea 2,2 MΩ m y para Q. scytophylla 19,6 MΩ m. Las magnitudes de las resistencias longitudinales medidas en las tres maderas son similares a las de las maderas reportadas en la literatura. Otro hallazgo fue que los valores de las resistividades muestran diferencias entre las direcciones de anisotropía de la madera y entre las especies estudiadas.

This research provides an analysis about the need to implement innovative alignment techniques and to diversify the methods to carry it out, if there is outdated equipment, misalignment becomes more recurrent and this causes the equipment to present failures as high vibration, high temperature, product leaks, excessive energy consumption and wear of some equipment components. In turn, this text exposes the methodologies of alignment of axes by straight edge, dial indicator, and by laser alignment, and makes a comparison of the advantages and disadvantages between these three methods to conclude which of them brings greater benefits to the industry today.

In the mechanical systems it is important to monitor the state of the components, to avoid breakdowns and cause forced stops in the system. Some of the processes that exist in different companies do not have monitoring and / or vibrations that allow for better inspection quality within a process. The project carried out has the purpose of studying and measuring possible bearing or bearing failures with technological equipment such as EPOCH III from Parametric. Therefore, it helps in training the student in the use of these equipments in order to recognize a fault.

On ancient Earth, environmental conditions favored prebiotic chemical reactions. In the Archean, some molecules with conjugated rings might have been synthesized, displaying structural stability in the Archean in the presence of ionizing radiation and hydration–dehydration events. Additionally, it is suggested that on ancient Earth, calcite was a common mineral promoting organic compound synthesis. In the present work a study of the interaction of amino acid mixtures with the (104) surface of calcite is presented. Our preliminary results show the abiotic synthesis of alloxazine (a flavin with relevant photochemical properties). Computer simulations were performed in HyperChem 8.0.1. by means of MM+ molecular mechanics and PM3 semi-empirical methods, in 27 possible amino acid trimers of alanine, glycine and lysine. Alloxazine formation is possible by the gamma irradiation of amino acids. The computer simulations show that trimers GGG and GGA promote the further transformation from diketopiperazines (DKP’s) and KGK to alloxazine. The computer simulations with free radicals are not stable when alloxazine is interacting with the calcite surface. Experiments in anoxygenic environments with hydration–dehydration events in gamma irradiated samples allow the abiotic formation of flavins, DKP’s and a heterocycle compound with possible relevance in prebiotic chemistry.

The objective was to design and create an airtight environment that disinfects objects and inactivates microorganisms with radiation, in addition to being easy to use and at a low cost. With a metallic structure, acrylic paint coatings, an acrylic sheet and a UV light lamp, which is controlled with a radiation sensor and another movement sensor. To be able to disinfect the interior of the box allowing to inactivate microorganisms at a low cost and easy handling. When using radiation as a disinfectant, microorganisms do not generate resistance and it is an easy- to-use method. The design was based on equipment used to disinfect, the design was carried out in design software, then an analysis of materials for its construction was carried out, taking into account radiation and other variables such as temperature. The results were the analysis of the correct function of the seals in the box, the power of the radiation to inactivate and the easy handling of the equipment.

El turismo es considerado un sector de alto crecimiento en Colombia desde hace una década aproximadamente, porque tiene la capacidad de involucrar un amplio sector de empresas (MiPymes) que se pueden vincular a la cadena turística, pero adolece de estrategias de marketing digital que permitan incursionar en el mercado actual. Así el objetivo de esta investigación es desarrollar productos turísticos con aplicaciones TIC (RA y RV) y con conceptos de neuromarketing, para insertarlos dentro de las estrategias de marketing digital. La metodología de investigación es exploratoria y descriptiva para el levantamiento del Estado del Arte, de donde se deriva el presente documento. A partir de esta información se hará la parte aplicada para un emprendimiento. Los resultados muestran la importancia de involucrar la innovación tecnológica para el turismo con estrategias claras de neuromarketing para que su inserción dentro del marketing digital sea exitosa para el desarrollo del turismo en un destino específico.

Free radicals are generated naturally in aerobic organisms as a result of mitochondrial activity. Normally, cells have many pathways for scavenging free radicals, but in certain pathologic processes, such as cancer, the development of free radicals increases, rendering it difficult to keep the system intact, resulting in oxidative stress. Ruta graveolens L. (Rue) is a plant widely used in traditional medicine, mostly as an anti-inflammatory; this has been linked to various organic components, such as Rutin, but no lectin tests in Rue stem have been conducted. The richest source for most lectins are the seeds or, more generally, the storage organs of plants. These are seeds as in most plants studied so far, but also roots, bark or leaves. Lectins are non-enzymatic, non-immune glycoproteins that can bind to simple carbohydrates, enabling them to bind selectively to malignant cells while killing them via apoptosis and reducing free radical levels. We aimed to classify rue stem lectins because they hadn't been studied before. The anticancer and antioxidant activity of these lectins was also investigated. Rue stem lectins were extracted using a saline solution and semipurified to obtain an enriched extract, which was then administered to nickel oxide-treated mice. Oxidative stress was quantified in the liver using the tiobarbituric acid (TBARS) method to quantify Malondialdehyde (MDA), the Griess method to quantify Nitrites, and the enzymatic activity of catalase. In this study, it was discovered that rue stem lectins are useful as a therapeutic auxiliar, despite the fact that their antioxidant activity ratio is limited, making them a prooxidant agent at high concentrations.

Summary Neurotrophins are related to survival, growth, differentiation and neurotrophic maintenance as well as modulation of synaptic transmission in different regions of the nervous system. BDNF effects have been studied in the striatum due to the trophic role of BDNF in medium spiny neurons; however, less is known about the effects of NT‐4/5, which is also present in the striatum and activates the TrkB receptor along with BDNF. If both neurotrophins are present in the striatum, the following question arises: What role do they play in striatal physiology? Thus, the aim of this study was to determine the physiological effect of the sequential application and coexistence of BDNF and NT‐4/5 on the modulation of corticostriatal synapses. Our data demonstrated that neurotrophins exhibit differential effects depending on exposure order. BDNF did not modify NT‐4/5 effect; however, NT‐4/5 inhibited the effects of BDNF. Experiments carried out in COS‐7 cells to understand the mechanisms of this antagonism, indicated that NT‐4/5 exerts its inhibitory effect on BDNF by upregulating the TrkB.T1 and downregulating the TrkB‐FL isoforms of the TrkB receptor.

The concentration of As, Pb, Cd, Zn, Fe, Mn, and Cu and the Sr and Pb isotopic compositions were determined in four species of the vascular epiphyte Tillandsia (T. caput medusae, T. ionantha, T. recurvata, and T. sp), to evaluate their capacity to biomonitor the air quality and the sources of lithogenic particles and toxic elements in a severely contaminated site from the mining region of Taxco de Alarcon, Guerrero (southern Mexico). With the exception of Cu, mean concentrations are typically higher in the contaminated site relative to a reference (uncontaminated) site, and the incrustation of metal-bearing particles (mainly PM10 and PM2.5) on leaves and roots seems to be the most significant mechanism of incorporation of these pollutants to plants. The Sr isotopic composition indicated that surrounding lithology is the main source of lithogenic particles, whereas statistical tools and Pb isotope ratios revealed a genetic link of toxic elements in epiphytes with Taxco ores and mining wastes, which confirm the capacity of the evaluated epiphytes to record local environmental conditions. The presence of abundant metal-bearing particles, particularly in the PM2.5, may represent a serious threat to the health of wild fauna, livestock, and humans in the zone. The study demonstrated that vascular epiphytes of the Tillandsia genus could be used as an efficient, low-cost, biotechnological tool for monitoring the air quality in severely contaminated polymetallic sites such as mining and smelting zones, as well as for sourcing lithogenic and metal-bearing particles.

This project aims to develop a filling system with automatic and manual mode, for filling domestic water tanks with an easy-to-use interface for the general public. A filling system was developed with the help of an ultrasonic sensor to measure the water level in the tank. The data obtained will be transferred and processed to the microcontroller of the Arduino program, this information will be represented graphically in the output device (LCD screen). For the control system, 2 buttons have been implemented to activate the automatic and manual modes, with this, it is possible to control the filling level of the water tank. This will allow us to know the advantages and disadvantages which will contribute to the formation of more solid knowledge regarding control systems.

This article presents a titration project describing the implementation in the rotodynamic equipment of an economical automated temperature module, as a preventive solution for future failures caused by the lack of analysis in the increase or decrease in temperature. The project is currently contextualized in the area of industry, first, providing background to frame the importance of temperature control and measurement and also know what its evolution has been like. Immediately focuses on explaining the theoretical basis for giving context to the reader. For the purpose of detecting the increase or decrease of heat in machinery by implementing a monitoring system. The development of the project is based on the use of an LM35 transistor that connected to an Arduino Uno through various cables, will display the temperature measurement and make interface of the obtained results that will be reflected in a 2x16 LCD screen. The project is applied in a prototype bench in three key parts of the pulley, and in the two bearings to make the simulations, then perform corresponding tests and check that theory. A simple and lower cost system, but above all efficient that meets the expectations of the problem presented.

Mitochondrial inhibition with the toxin 3-Nitropropionic acid (3-NP) has been used to study the underlying mechanisms in striatal neurodegeneration, but few experiments have evaluated its toxicity and genotoxicity of in vivo administration. Furthermore, different antioxidant molecules may prevent degeneration induced by the toxic effects of 3-NP. Therefore, the purpose of this study was to evaluate the toxicity and genotoxicity induced by 3-NP (15 mg/kg) in the micronuclei assay method; also, we assessed chlorogenic acid (CGA, 100 mg/kg) for its anti-toxic and anti-genotoxic effect in damage produced by in vivo treatment with 3-NP. 3-NP induced toxicity and genotoxicity. CGA administered as a co-treatment with 3-NP (3-NP + CA) reduced toxicity by 32.76%, as a pre-treatment for 5 days only, followed by 3-NP treatment (P/CA, 3-NP) inhibiting toxicity by 24.04%, or as a pre-treatment, plus a co-treatment with 3-NP (P/CA, 3-NP + CA) avoided any toxic effect. CGA alone did not exhibit any toxic effect. Only P/CGA, 3-NP + CGA group, avoided toxicity and genotoxicity, suggesting that CGA could be suitable to prevent, reduce or delay toxicity and cell death.

Brain-derived neurotrophic factor (BDNF) and neurotrophin-4/5 (NT-4/5) are trophic factors belonging to the neurotrophin family; in addition to their trophic role, both neurotrophins play an important role in modulating corticostriatal synaptic transmission. Failures in BDNF supply and mitochondrial dysfunction are among the factors involved in the striatal degeneration that occurs in Huntington's disease (HD). While the effects of BDNF have been widely studied in striatal degeneration, the role of NT-4/5 has been less addressed. NT-4/5 does not appear to exert effects similar to those of BDNF in HD. The physiological roles of these molecules in corticostriatal transmission have been evaluated separately, and we have demonstrated that sequential exposure to both neurotrophins results in different modulatory effects on corticostriatal transmission depending on the exposure order. In the present study, we evaluated the effects of BDNF followed by NT-4/5 or NT-4/5 followed by BDNF on corticostriatal synaptic transmission with field recordings in a male mouse model of HD produced by in vivo treatment with the mitochondrial toxin 3-nitropropionic acid. Here, we show that these neurotrophins elicit an antagonistic or synergistic effect that depends on the activation of the truncated isoform or the stimulation of the full-length isoform of the tropomyosin receptor kinase B.

OBJETIVO: Determinar la tasa de éxito y las complicaciones relacionadas con la nefrolitotomía percutánea.MATERIALES Y MÉTODOS: Estudio transversal y analítico, efectuado en pacientes intervenidos de nefrolitotomía percutánea, atendidos en el Hospital Regional Dr. Valentín Gómez Farías, entre marzo de 2014 y octubre de 2017. Se analizaron variables como: edad, sexo, riñón afectado, antecedente de cirugía renal o litotricia extracorpórea y comorbilidades asociadas, además de las características, localización y microbiología de los cálculos renales; la tasa libre de cálculos y complicaciones. Para el análisis de los datos se utilizó el programa estadístico SPSS, versión 10; se implementó la prueba exacta de Fisher y se consideró estadísticamente significativo el valor de p

Experimental evidence has revealed the role of mitochondria in various aspects of neuronal physiology. Mitochondrial failure results in alterations that underlie the pathogeneses of many neurodegenerative disorders, such as Parkinson's disease, Alzheimer's disease, Huntington's disease (HD) and amyotrophic lateral sclerosis. The mitochondrial toxin 3-nitropropionic acid (3-NP) has been used to model failure; for example, systemic administration of 3-NP imitates the striatal degeneration that is exhibited in the postmortem tissue of patients afflicted with HD. We have demonstrated that low, sub-chronic doses of 3-NP are sufficient to initiate the damage to striatal neurons that is associated with changes in neurotrophin expression levels. However, the mechanisms underlying the alterations in neuronal activity and neurotransmission due to 3-NP-induced mitochondrial dysfunction remain to be elucidated. In this paper, we focus on how corticostriatal transmission and its modulation by neurotrophins are altered in vivo after 5 days of mitochondrial inhibition with 3-NP. Recordings of population spikes and a paired pulse (PP) stimulation protocol were used to document changes in corticostriatal synapses in 3-NP-treated brain slices. The corticostriatal synapses were modulated by neurotrophins but displayed differential amplitude increases in the presence of brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), or neurotrophin-4/5 (NT-4/5) under control conditions. Neurotrophin-mediated synaptic modulation was decreased in slices from 3-NP-treated mice. The protein and mRNA levels of neurotrophins and their receptors were also modified in the 3-NP-treated tissue. Neuronal structural evaluation demonstrated that synaptic length and density were reduced in the 3-NP-treated mice, which partially explained the changes in the amplitudes of the synaptic field responses. Our results demonstrate that corticostriatal synapses are differentially modulated by neurotrophins and that this modulation is altered by mitochondrial failure. Mitochondrial dysfunction also affects neurotransmitter release in corticostriatal synapses, neurotrophin availability, dendritic arborization and the lengths of the striatal medium spiny neurons (MSNs).

Low-crested detached breakwaters (LCDBs) have been widely employed as a mitigation measure against beach erosion. However, only a few studies have assessed their performance in sea-breeze-dominated environments. This work investigates the beach morphodynamics behind LCDBs deployed on a micro-tidal sea-breeze-dominated beach. The study area, located in the northern Yucat&aacute, n peninsula, is characterized by low-energy, high-angle waves, which drive a persistent (westward) alongshore sediment transport (O(104) m3/year). High-resolution real-time kinematics global positioning system (GPS) beach surveys were conducted over a one-year period (2017&ndash, 2018) to investigate the performance of LCDBs at three sites. Moreover, unmanned aerial vehicle flights were employed to evaluate far-field shoreline stability. Field observations revealed a distinct behavior in the three study sites, dependent on the breakwaters&rsquo, transmission characteristics, geometry, stability, and shoreline orientation. Impermeable LCDBs, made of sand-filled geosystems, induced significant beach accretion (erosion) in up-(down-)drift areas. On the other hand, permeable LCDBs, made of Reef Ball&trade, modules, induced moderate beach changes and small erosion in down-drift areas owing to higher transmission coefficients. Measurements of LCDBs&rsquo, freeboard height show that sand-filled geosystems&rsquo, breakwaters presented a significant loss of sand during the study period, which explains the unexpected beach morphodynamic response on the lee side of the structure. Observations suggest that the study area is highly sensitive to the presence of LCDBs with low transmissivity.

The aim of this paper is the development of a method to predict interfacial failure in adhesive joints. The main originality of the paper resides on the application of a twofold criterion involving stress and energy conditions simultaneously to predict adhesive failure onset in different geometries of adhesive joints subjected to diverse loadings. Butt joints and double lap joints made of linear elastic materials are tested in torsion and tension. The failure onset predictions are based on finite element calculations and a twofold criterion which considers a novel stress condition. These predictions are accurate and prove the validity of the method to predict adhesive failure for different adhesive joint configurations and loadings.

The author starts by revising the concept of public service, highlighting the idea of publicatio as an important element. With this taken into consideration, he points out that it is not possible to understand the concept of public service without the presence of ownership by the State. In this context, the concept of essential service arises as a technique that harmonizes social demands and the traditional conception of public service. All in all, these concepts are materialized to affirm that the nature of the service of drinking water and sanitation is of essential service, developing and applying its principles to the concrete case. El autor parte por una revisión del concepto objetivo de servicio público, destacando como un elemento importante de este la idea de publicatio. A partir de ello, señala que no es posible entender el concepto de servicio público sin la presencia de la titularidad por parte del Estado. En este contexto, surge el concepto de servicio esencial como una técnica que armoniza las exigencias sociales y la concepción tradicional de servicio público. Finalmente, aterriza dichos conceptos para afirmar que la naturaleza del servicio de provisión de agua potable y saneamiento es de servicio esencial, desarrollando y aplicando sus principios al caso concreto.

A variety of evidence suggests that the failure of cellular metabolism is one of the underlying causes of neurodegenerative diseases. For example, the inhibition of mitochondrial function produces a pattern of cellular pathology in the striatum that resembles that seen in Huntington's disease. However, neurons can also generate ATP through the glycolytic pathway. Recent work has suggested a direct interaction between mutated huntingtin and a key enzyme in the glycolytic pathway, glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Yet little work has been gone into examination of the cellular pathology that results from the inhibition of this alternative energy source. Therefore, the aim of the present study is to characterize the cellular pathology that results in the striatum of mice after treatment with a toxin (iodoacete, IOA) that compromises anaerobic metabolism. This striatal pathology is compared to that produced by a widely studied blocker of mitochondrial function (3-nitropropionic acid, 3-NP). We found that low doses of either toxin resulted in significant pathology in the mouse striatum. Signs of apoptosis were observed in both experimental groups, although apoptosis triggered by IOA treatment was independent from caspase-3 activation. Importantly, each toxin appears to produce cellular damage through distinct mechanisms; only 3-NP generated clear evidence of oxidative stress as well as inhibition of endogenous antioxidants. Understanding the distinct pathological fingerprints of cell loss produced by blockade of oxidative and anaerobic metabolisms may give us insights into neurodegenerative diseases.

Procedural memories and habits are posited to be stored in the basal ganglia, whose intrinsic circuitries possess important inhibitory connections arising from striatal spiny neurons. However, no information about long-term plasticity at these synapses is available. Therefore, this work describes a novel postsynaptically dependent long-term potentiation (LTP) at synapses among spiny neurons (intrinsic striatal circuitry); a postsynaptically dependent long-term depression (LTD) at synapses between spiny and pallidal neurons (indirect pathway); and a presynaptically dependent LTP at strionigral synapses (direct pathway). Interestingly, long-term synaptic plasticity differs at these synapses. The functional consequences of these long-term plasticity variations during learning of procedural memories are discussed.

Neurotrophin expression in early stages of development is crucial for brain assembly and function. In particular, postnatal expression of neurotrophins has not been well documented in the neostriatum and in general neurotrophins or their receptor mRNA's are normally reported, but not protein expression. In the present study, immunocytochemical expression of BDNF, NT-3 and NT-4/5 was characterized in striatal tissue of C57BL/6 mice at postnatal days 10(th )(P10), 21(st) (P21), 42(nd) (P42) and 80(th) (P80). We found that the expression of BDNF diminished along the postnatal time course we evaluated, while staining for NT-4 increased up to age P42 and remained constant, thereafter in the cell's soma. In contrast, NT-3 was first expressed in the neostriatal bundles and later on, in neostriatal cell somas. These results provide information about differences in the spatial and temporal expression of each neurotrophin in the neostriatum during the first 80(th) postnatal days. RT-PCR procedures were also carried out to further determine whether protein levels of neurotrophins observed in the neostriatum were under control of gene expression. All neurotrophin mRNAs were expressed and only mRNA(BDNF) was reduced during the postnatal evaluated days. Differences in temporal expression of neurotrophins may be related to the heterochronic development of neostriatal cell populations, but also with the specificity of each neurotrophin modulating different neuronal targets.

Projection neurons of the substantia nigra reticulata (SNr) convey basal ganglia (BG) processing to thalamocortical and brain stem circuits responsible for movement. Two models try to explain pathological BG performance during Parkinson disease (PD): the rate model, which posits an overexcitation of SNr neurons due to hyperactivity in the indirect pathway and hypoactivity of the direct pathway, and the oscillatory model, which explains PD as the product of pathological pattern generators disclosed by dopamine reduction. These models are, apparently, incompatible. We tested the predictions of the rate model by increasing the excitatory drive and reducing the inhibition on SNr neurons in vitro. This was done pharmacologically with bath application of glutamate agonist N-methyl-d-aspartate and GABAA receptor blockers, respectively. Both maneuvers induced bursting behavior in SNr neurons. Therefore synaptic changes forecasted by the rate model induce the electrical behavior predicted by the oscillatory model. In addition, we found evidence that CaV3.2 Ca2+ channels are a critical step in generating the bursting firing pattern in SNr neurons. Other ion channels involved are: hyperpolarization-activated cation channels, high-voltage-activated Ca2+ channels, and Ca2+-activated K+ channels. However, although these channels shape the temporal structure of bursting, only CaV3.2 Ca2+ channels are indispensable for the initiation of the bursting pattern.

Long term synaptic plasticity has been more extensively studied in excitatory synapses, but it is also a property of inhibitory synapses. Many inhibitory synapses target hippocampal pyramidal neurons of the CA1 region. They originate from several interneuron classes that subdivide the surface area that they target on the pyramidal cell. Thus, many interneurons preferentially innervate the perisomatic area and axon hillock of the pyramidal cells while others preferentially target dendritic branches and spines. Methods to preferentially activate dendritic or somatic inhibitory synapses onto pyramidal neurons have been devised. By using these methods, the present work demonstrates that a stimulation pattern that induces long term potentiation (LTP) in excitatory synapses of the Schaffer collaterals is also capable of inducing distinct types of long term plastic changes in different classes of inhibitory synapses: Induction of long term depression (LTD) was seen in dendritic inhibitory synapses whereas LTP was observed in somatic inhibitory synapses. These findings suggest that inhibitory synapses arising from different interneuron classes may respond to the same stimulus according to their specific plastic potential enabling a spatial combinatorial pattern of inhibitory effects onto the pyramidal cell.

Population spikes associated with the paired pulse ratio protocol were used to measure the presynaptic inhibition of corticostriatal transmission caused by mu-opioid receptor activation. A 1 microM of [D-Ala(2), N-MePhe(4), Gly-ol(5)]-enkephalin (DAMGO), a selective mu-opioid receptor agonist, enhanced paired pulse facilitation by 44+/-8%. This effect was completely blocked by 2 nM of the selective mu-receptor antagonist D-Phe-Cys-Tyr-D-Trp-Orn-Thr-NH (CTOP). Antagonists of N- and P/Q-type Ca(2+) channels inhibited, whereas antagonists of potassium channels enhanced, synaptic transmission. A 1 microM of omega-conotoxin GVIA, a blocker of N-type Ca(2+) channels, had no effect on the action of DAMGO, but 400 nM omega-agatoxin TK, a blocker of P/Q-type Ca(2+)-channels, partially blocked the action of this opioid. However, 5 mM Cs(2+) and 400 microM Ba(2+), unselective antagonists of potassium conductances, completely prevented the action of DAMGO on corticostriatal transmission. These data suggest that presynaptic inhibition of corticostriatal afferents by mu-opioids is mediated by the modulation of K(+) conductances in corticostriatal afferents.