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1.
Adv Exp Med Biol ; 1131: 73-91, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-31646507

RESUMEN

Imaging techniques may overcome the limitations of electrode techniques to measure locally not only membrane potential changes, but also ionic currents. Here, we review a recently developed approach to image native neuronal Ca2+ currents from brain slices. The technique is based on combined fluorescence recordings using low-affinity Ca2+ indicators possibly in combination with voltage sensitive dyes. We illustrate how the kinetics of a Ca2+ current can be estimated from the Ca2+ fluorescence change and locally correlated with the change of membrane potential, calibrated on an absolute scale, from the voltage fluorescence change. We show some representative measurements from the dendrites of CA1 hippocampal pyramidal neurons, from olfactory bulb mitral cells and from cerebellar Purkinje neurons. We discuss the striking difference in data analysis and interpretation between Ca2+ current measurements obtained using classical electrode techniques and the physiological currents obtained using this novel approach. Finally, we show how important is the kinetic information on the native Ca2+ current to explore the potential molecular targets of the Ca2+ flux from each individual Ca2+ channel.


Asunto(s)
Canales de Calcio , Neuroimagen , Animales , Calcio/metabolismo , Canales de Calcio/fisiología , Dendritas/fisiología , Humanos , Potenciales de la Membrana/fisiología , Imagen Óptica , Células Piramidales/fisiología
2.
Nat Neurosci ; 22(11): 1883-1891, 2019 11.
Artículo en Inglés | MEDLINE | ID: mdl-31570859

RESUMEN

When making decisions we often face the need to adjudicate between conflicting strategies or courses of action. Our ability to understand the neuronal processes underlying conflict processing is limited on the one hand by the spatiotemporal resolution of functional MRI and, on the other hand, by imperfect cross-species homologies in animal model systems. Here we examine the responses of single neurons and local field potentials in human neurosurgical patients in two prefrontal regions critical to controlled decision-making, the dorsal anterior cingulate cortex (dACC) and dorsolateral prefrontal cortex (dlPFC). While we observe typical modest conflict-related firing rate effects, we find a widespread effect of conflict on spike-phase coupling in the dACC and on driving spike-field coherence in the dlPFC. These results support the hypothesis that a cross-areal rhythmic neuronal coordination is intrinsic to cognitive control in response to conflict, and provide new evidence to support the hypothesis that conflict processing involves modulation of the dlPFC by the dACC.


Asunto(s)
Cognición/fisiología , Giro del Cíngulo/fisiología , Corteza Prefrontal/fisiología , Factores de Tiempo , Femenino , Humanos , Masculino , Potenciales de la Membrana/fisiología , Vías Nerviosas/fisiología , Neuronas/fisiología
3.
Nat Neurosci ; 22(12): 1975-1985, 2019 12.
Artículo en Inglés | MEDLINE | ID: mdl-31611707

RESUMEN

The increased legal availability of cannabis has led to a common misconception that it is a safe natural remedy for, among others, pregnancy-related ailments such as morning sickness. Emerging clinical evidence, however, indicates that prenatal cannabis exposure (PCE) predisposes offspring to various neuropsychiatric disorders linked to aberrant dopaminergic function. Yet, our knowledge of how cannabis exposure affects the maturation of this neuromodulatory system remains limited. Here, we show that male, but not female, offspring of Δ9-tetrahydrocannabinol (THC)-exposed dams, a rat PCE model, exhibit extensive molecular and synaptic changes in dopaminergic neurons of the ventral tegmental area, including altered excitatory-to-inhibitory balance and switched polarity of long-term synaptic plasticity. The resulting hyperdopaminergic state leads to increased behavioral sensitivity to acute THC exposure during pre-adolescence. The neurosteroid pregnenolone, a US Food and Drug Administration (FDA) approved drug, rescues synaptic defects and normalizes dopaminergic activity and behavior in PCE offspring, thus suggesting a therapeutic approach for offspring exposed to cannabis during pregnancy.


Asunto(s)
Neuronas Dopaminérgicas/metabolismo , Dronabinol/efectos adversos , Dronabinol/farmacología , Pregnenolona/farmacología , Efectos Tardíos de la Exposición Prenatal/metabolismo , Animales , Dopamina/metabolismo , Neuronas Dopaminérgicas/fisiología , Dronabinol/antagonistas & inhibidores , Endofenotipos , Femenino , Aprendizaje por Laberinto/efectos de los fármacos , Potenciales de la Membrana/fisiología , Actividad Motora/efectos de los fármacos , Inhibición Neural/fisiología , Plasticidad Neuronal/efectos de los fármacos , Núcleo Accumbens/metabolismo , Embarazo , Inhibición Prepulso/efectos de los fármacos , Inhibición Prepulso/fisiología , Ratas , Asunción de Riesgos , Filtrado Sensorial/efectos de los fármacos , Filtrado Sensorial/fisiología , Caracteres Sexuales , Área Tegmental Ventral/metabolismo
4.
Neural Netw ; 119: 66-73, 2019 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-31401527

RESUMEN

Grid cells in the medial entorhinal cortex (MEC) have known spatial periodic firing fields which provide a metric for the representation of self-location and path planning. The hexagonal tessellation pattern of grid cells scales up progressively along the MEC's layer II dorsal-to-ventral axis. This scaling gradient has been hypothesized to originate either from inter-population synaptic dynamics as postulated by attractor networks, or from projected theta frequency waves to different axis levels, as in oscillatory models. Alternatively, cellular dynamics and specifically slow high-threshold conductances have been proposed to have an impact on the grid cell scale. To test the hypothesis that intrinsic hyperpolarization-activated cation currents account for both the scaled gradient and the oscillatory frequencies observed along the dorsal-to-ventral axis, we have modeled and analyzed data from a population of grid cells simulated with spiking neurons interacting through low-dimensional attractor dynamics. We observed that the intrinsic neuronal membrane properties of simulated cells were sufficient to induce an increase in grid scale and potentiate differences in the membrane potential oscillatory frequency. Overall, our results suggest that the after-spike dynamics of cation currents may play a major role in determining the grid cells' scale and that oscillatory frequencies are a consequence of intrinsic cellular properties that are specific to different levels of the dorsal-to-ventral axis in the MEC layer II.


Asunto(s)
Potenciales de Acción , Corteza Entorrinal , Células de Red , Modelos Neurológicos , Potenciales de Acción/fisiología , Animales , Corteza Entorrinal/citología , Corteza Entorrinal/fisiología , Células de Red/fisiología , Humanos , Potenciales de la Membrana/fisiología , Neuronas/fisiología
5.
Nat Commun ; 10(1): 3584, 2019 08 08.
Artículo en Inglés | MEDLINE | ID: mdl-31395867

RESUMEN

In voltage-gated potassium channels (VGKC), voltage sensors (VSD) endow voltage-sensitivity to pore domains (PDs) through a not fully understood mechanism. Shaker-like VGKC show domain-swapped configuration: VSD of one subunit is covalently connected to its PD by the protein backbone (far connection) and non-covalently to the PD of the next subunit (near connection). VSD-to-PD coupling is not fully explained by far connection only, therefore an additional mechanistic component may be based on near connection. Using tandem dimers of Shaker channels we show functional data distinguishing VSD-to-PD far from near connections. Near connections influence both voltage-dependence of C-type inactivation at the selectivity filter and overall PD open probability. We speculate a conserved residue in S5 (S412 in Shaker), within van der Waals distance from next subunit S4 residues is key for the noncanonical VSD-to-PD coupling. Natural mutations of S412-homologous residues in brain and heart VGKC are related to neurological and cardiac diseases.


Asunto(s)
Activación del Canal Iónico/fisiología , Multimerización de Proteína/fisiología , Canales de Potasio de la Superfamilia Shaker/metabolismo , Animales , Femenino , Potenciales de la Membrana/fisiología , Mutagénesis , Oocitos , Dominios Proteicos/genética , Canales de Potasio de la Superfamilia Shaker/genética , Xenopus laevis
6.
Neural Netw ; 119: 200-213, 2019 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-31450073

RESUMEN

An increasing body of evidence suggests that the trial-to-trial variability of spiking activity in the brain is not mere noise, but rather the reflection of a sampling-based encoding scheme for probabilistic computing. Since the precise statistical properties of neural activity are important in this context, many models assume an ad-hoc source of well-behaved, explicit noise, either on the input or on the output side of single neuron dynamics, most often assuming an independent Poisson process in either case. However, these assumptions are somewhat problematic: neighboring neurons tend to share receptive fields, rendering both their input and their output correlated; at the same time, neurons are known to behave largely deterministically, as a function of their membrane potential and conductance. We suggest that spiking neural networks may have no need for noise to perform sampling-based Bayesian inference. We study analytically the effect of auto- and cross-correlations in functional Bayesian spiking networks and demonstrate how their effect translates to synaptic interaction strengths, rendering them controllable through synaptic plasticity. This allows even small ensembles of interconnected deterministic spiking networks to simultaneously and co-dependently shape their output activity through learning, enabling them to perform complex Bayesian computation without any need for noise, which we demonstrate in silico, both in classical simulation and in neuromorphic emulation. These results close a gap between the abstract models and the biology of functionally Bayesian spiking networks, effectively reducing the architectural constraints imposed on physical neural substrates required to perform probabilistic computing, be they biological or artificial.


Asunto(s)
Teorema de Bayes , Encéfalo/fisiología , Potenciales de la Membrana/fisiología , Modelos Neurológicos , Neuronas/fisiología , Simulación por Computador , Plasticidad Neuronal/fisiología
7.
PLoS Comput Biol ; 15(8): e1006938, 2019 08.
Artículo en Inglés | MEDLINE | ID: mdl-31469828

RESUMEN

The mechanism(s) of action of most commonly used pharmacological blockers of voltage-gated ion channels are well understood; however, this knowledge is rarely considered when interpreting experimental data. Effects of blockade are often assumed to be equivalent, regardless of the mechanism of the blocker involved. Using computer simulations, we demonstrate that this assumption may not always be correct. We simulate the blockade of a persistent sodium current (INaP), proposed to underlie rhythm generation in pre-Bötzinger complex (pre-BötC) respiratory neurons, via two distinct pharmacological mechanisms: (1) pore obstruction mediated by tetrodotoxin and (2) altered inactivation dynamics mediated by riluzole. The reported effects of experimental application of tetrodotoxin and riluzole in respiratory circuits are diverse and seemingly contradictory and have led to considerable debate within the field as to the specific role of INaP in respiratory circuits. The results of our simulations match a wide array of experimental data spanning from the level of isolated pre-BötC neurons to the level of the intact respiratory network and also generate a series of experimentally testable predictions. Specifically, in this study we: (1) provide a mechanistic explanation for seemingly contradictory experimental results from in vitro studies of INaP block, (2) show that the effects of INaP block in in vitro preparations are not necessarily equivalent to those in more intact preparations, (3) demonstrate and explain why riluzole application may fail to effectively block INaP in the intact respiratory network, and (4) derive the prediction that effective block of INaP by low concentration tetrodotoxin will stop respiratory rhythm generation in the intact respiratory network. These simulations support a critical role for INaP in respiratory rhythmogenesis in vivo and illustrate the importance of considering mechanism when interpreting and simulating data relating to pharmacological blockade.


Asunto(s)
Modelos Neurológicos , Sistema Respiratorio/efectos de los fármacos , Sistema Respiratorio/inervación , Bloqueadores de los Canales de Sodio/farmacología , Animales , Biología Computacional , Simulación por Computador , Técnicas In Vitro , Potenciales de la Membrana/efectos de los fármacos , Potenciales de la Membrana/fisiología , Red Nerviosa/efectos de los fármacos , Red Nerviosa/fisiología , Neuronas/efectos de los fármacos , Neuronas/fisiología , Centro Respiratorio/efectos de los fármacos , Centro Respiratorio/fisiología , Sistema Respiratorio/metabolismo , Riluzol/farmacología , Canales de Sodio/metabolismo , Transmisión Sináptica/efectos de los fármacos , Transmisión Sináptica/fisiología , Tetrodotoxina/farmacología
8.
Mol Cell ; 75(5): 1031-1042.e4, 2019 09 05.
Artículo en Inglés | MEDLINE | ID: mdl-31327636

RESUMEN

Every bacterial population harbors a small subpopulation of so-called persisters that are transiently antibiotic tolerant. These persisters are associated with the recalcitrance of chronic infections because they can recolonize the host after antibiotic removal. Although several effectors have been described to induce persistence, persister cell awakening is poorly understood. We previously reported that the toxin HokB induces persistence via pore formation, resulting in membrane depolarization and ATP leakage. We now delineate mechanisms responsible for the awakening of HokB-induced persisters. We show that HokB dimerization by the oxidoreductase DsbA is essential for pore formation and peptide stability. Pores are disassembled via DsbC-mediated monomerization, which targets HokB for DegQ-mediated degradation. Finally, pore disassembly allows membrane repolarization by the electron transport chain, supporting cells to resume growth. These results provide a detailed view of both the formation and awakening of HokB-induced persister cells.


Asunto(s)
Toxinas Bacterianas/metabolismo , Membrana Celular/metabolismo , Proteínas de Escherichia coli/metabolismo , Escherichia coli/metabolismo , Potenciales de la Membrana/fisiología , Proteolisis , Serina Endopeptidasas/metabolismo , Toxinas Bacterianas/genética , Membrana Celular/genética , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Proteína Disulfuro Isomerasas/genética , Proteína Disulfuro Isomerasas/metabolismo , Serina Endopeptidasas/genética
9.
Muscle Nerve ; 60(4): 433-436, 2019 10.
Artículo en Inglés | MEDLINE | ID: mdl-31330047

RESUMEN

INTRODUCTION: The sarcolemmal resting membrane potential (RMP) affects muscle excitability, contractility, and force generation. However, there are limited In vivo data on the normal RMP of the human sarcolemma between muscles. We hypothesize that the in vivo RMP may differ between human muscles with different physiological roles. METHODS: Muscle velocity recovery cycles were recorded from a proximal antigravity muscle, the rectus femoris, and compared with paired recordings from a distal non-antigravity muscle, the tibialis anterior, in 34 normal individuals. RESULTS: Significant differences in muscle relative refractory period (3.55 millseconds vs 3.87 milliseconds, P = .002), early supernormality (14.22% vs 10.50%, P < .0001), and late supernormality (5.43% vs 3.50%, P < .0001) were observed. DISCUSSION: The results strongly suggest a less negative RMP in tibialis anterior vs rectus femoris and attest to intermuscle differences in normal excitability and physiology. This novel finding employing an in vivo methodology highlights the need for muscle-specific normative data in future studies.


Asunto(s)
Potenciales de la Membrana/fisiología , Músculo Cuádriceps/fisiología , Periodo Refractario Electrofisiológico/fisiología , Sarcolema/fisiología , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Masculino , Persona de Mediana Edad , Músculo Esquelético/fisiología , Valores de Referencia , Adulto Joven
10.
BMC Neurosci ; 20(1): 35, 2019 07 22.
Artículo en Inglés | MEDLINE | ID: mdl-31331291

RESUMEN

BACKGROUND: The functional heterogeneity of the hippocampus along its longitudinal axis at the level of behavior is an established concept; however, the neurobiological mechanisms are still unknown. Diversifications in the functioning of intrinsic hippocampal circuitry including short-term dynamics of synaptic inputs and neuronal output, that are important determinants of information processing in the brain, may profoundly contribute to functional specializations along the hippocampus. The objectives of the present study were the examination of the role of the GABAA receptor-mediated inhibition, the µ-opioid receptors and the effect of stimulation intensity on the dynamics of both synaptic input and neuronal output of CA1 region in the dorsal and ventral hippocampus. We used recordings of field potentials from adult rat hippocampal slices evoked by brief repetitive activation of Schaffer collaterals. RESULTS: We find that the local CA1 circuit of the dorsal hippocampus presents a remarkably increased dynamic range of frequency-dependent short-term changes in both input and output, ranging from strong facilitation to intense depression at low and high stimulation frequencies respectively. Furthermore, the input-output relationship in the dorsal CA1 circuit is profoundly influenced by frequency and time of presynaptic activation. Strikingly, the ventral hippocampus responds mostly with depression, displaying a rather monotonous input-output relationship over frequency and time. Partial blockade of GABAA receptor-mediated transmission (by 5 µM picrotoxin) profoundly influences input and output dynamics in the dorsal hippocampus but affected only the neuronal output in the ventral hippocampus. M-opioid receptors control short-term dynamics of input and output in the dorsal hippocampus but they play no role in the ventral hippocampus. CONCLUSION: The results demonstrate that information processing by CA1 local network is highly diversified between the dorsal and ventral hippocampus. Transient detection of incoming patterns of activity and frequency-dependent sustained signaling of amplified neuronal information may be assigned to the ventral and dorsal hippocampal circuitry respectively. This disparity should have profound implications for the functional roles ascribed to distinct segments along the long axis of the hippocampus.


Asunto(s)
Región CA1 Hipocampal/fisiología , Hipocampo/fisiología , Receptores de GABA-A/fisiología , Receptores Opioides mu/fisiología , Animales , Estimulación Eléctrica , Antagonistas de Receptores de GABA-A/farmacología , Masculino , Potenciales de la Membrana/fisiología , Vías Nerviosas/fisiología , Picrotoxina/farmacología , Ratas
11.
Neurochem Res ; 44(8): 1999-2006, 2019 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-31325154

RESUMEN

Adult-onset hypothyroidism induces cognitive impairments in learning and memory. Thyroxin (T4) replacement therapy appears to be effective in biochemically restoring euthyroidism, as evidenced by serum T4 and triiodothyronine concentrations within the normal range, although some the patients still exhibit cognitive dysfunctions. Here, we investigated the cognitive functions of propylthiouracil-induced hypothyroid mice in C57BL/6j and 129/Sv strains using the passive avoidance task and the novel object recognition test. Cognitive dysfunctions in hypothyroid mice were found only in the C57BL/6j strain, not in the 129/Sv strain. Further, we found that cholinergic neurons in the basal forebrain increased the membrane potential and input resistance with decreased capacitance, and that they decreased the amplitude and width of action potential in hypothyroid mice in the C57BL/6j strain but not in those in the 129/Sv strain, compared with the controls for each strain. Additionally, the excitability of cholinergic neurons in the basal forebrain was reduced in the hypothyroid mice in the C57BL/6j strain. These results indicated that transgenic mice with the C57BL/6j genetic background are more suitable for revealing the mechanism underlying hypothyroidism-induced cognitive dysfunction, and that the cholinergic basal forebrain may be the appropriate target for treating cognitive dysfunction in adult-onset hypothyroidism.


Asunto(s)
Disfunción Cognitiva/fisiopatología , Modelos Animales de Enfermedad , Hipotiroidismo/fisiopatología , Ratones de la Cepa 129/genética , Ratones Endogámicos C57BL/genética , Ratones Transgénicos/genética , Animales , Prosencéfalo Basal/metabolismo , Neuronas Colinérgicas/metabolismo , Disfunción Cognitiva/etiología , Hipotiroidismo/inducido químicamente , Hipotiroidismo/complicaciones , Aprendizaje/fisiología , Masculino , Potenciales de la Membrana/fisiología , Memoria/fisiología , Propiltiouracilo , Hormonas Tiroideas/metabolismo
12.
Nat Commun ; 10(1): 2659, 2019 06 14.
Artículo en Inglés | MEDLINE | ID: mdl-31201323

RESUMEN

In contrast to the plasma membrane, the vacuole membrane has not yet been associated with electrical excitation of plants. Here, we show that mesophyll vacuoles from Arabidopsis sense and control the membrane potential essentially via the K+-permeable TPC1 and TPK channels. Electrical stimuli elicit transient depolarization of the vacuole membrane that can last for seconds. Electrical excitability is suppressed by increased vacuolar Ca2+ levels. In comparison to wild type, vacuoles from the fou2 mutant, harboring TPC1 channels insensitive to luminal Ca2+, can be excited fully by even weak electrical stimuli. The TPC1-loss-of-function mutant tpc1-2 does not respond to electrical stimulation at all, and the loss of TPK1/TPK3-mediated K+ transport affects the duration of TPC1-dependent membrane depolarization. In combination with mathematical modeling, these results show that the vacuolar K+-conducting TPC1 and TPK1/TPK3 channels act in concert to provide for Ca2+- and voltage-induced electrical excitability to the central organelle of plant cells.


Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/fisiología , Canales de Calcio/metabolismo , Potenciales de la Membrana/fisiología , Vacuolas/fisiología , Proteínas de Arabidopsis/genética , Canales de Calcio/genética , Señalización del Calcio/fisiología , Membranas Intracelulares/fisiología , Mutación con Pérdida de Función , Células del Mesófilo/citología , Células del Mesófilo/fisiología , Plantas Modificadas Genéticamente , Potasio/metabolismo , Canales de Potasio/metabolismo , Canales de Potasio de Dominio Poro en Tándem/metabolismo
13.
BMC Dev Biol ; 19(1): 12, 2019 06 21.
Artículo en Inglés | MEDLINE | ID: mdl-31226923

RESUMEN

BACKGROUND: Alterations of bioelectrical properties of cells and tissues are known to function as wide-ranging signals during development, regeneration and wound-healing in several species. The Drosophila follicle-cell epithelium provides an appropriate model system for studying the potential role of electrochemical signals, like intracellular pH (pHi) and membrane potential (Vmem), during development. Therefore, we analysed stage-specific gradients of pHi and Vmem as well as their dependence on specific ion-transport mechanisms. RESULTS: Using fluorescent indicators, we found distinct alterations of pHi- and Vmem-patterns during stages 8 to 12 of oogenesis. To determine the roles of relevant ion-transport mechanisms in regulating pHi and Vmem and in establishing stage-specific antero-posterior and dorso-ventral gradients, we used inhibitors of Na+/H+-exchangers and Na+-channels (amiloride), V-ATPases (bafilomycin), ATP-sensitive K+-channels (glibenclamide), voltage-dependent L-type Ca2+-channels (verapamil), Cl--channels (9-anthroic acid) and Na+/K+/2Cl--cotransporters (furosemide). Either pHi or Vmem or both parameters were affected by each tested inhibitor. While the inhibition of Na+/H+-exchangers (NHE) and amiloride-sensitive Na+-channels or of V-ATPases resulted in relative acidification, inhibiting the other ion-transport mechanisms led to relative alkalisation. The most prominent effects on pHi were obtained by inhibiting Na+/K+/2Cl--cotransporters or ATP-sensitive K+-channels. Vmem was most efficiently hyperpolarised by inhibiting voltage-dependent L-type Ca2+-channels or ATP-sensitive K+-channels, whereas the impact of the other ion-transport mechanisms was smaller. In case of very prominent effects of inhibitors on pHi and/or Vmem, we also found strong influences on the antero-posterior and dorso-ventral pHi- and/or Vmem-gradients. For example, inhibiting ATP-sensitive K+-channels strongly enhanced both pHi-gradients (increasing alkalisation) and reduced both Vmem-gradients (increasing hyperpolarisation). Similarly, inhibiting Na+/K+/2Cl--cotransporters strongly enhanced both pHi-gradients and reduced the antero-posterior Vmem-gradient. To minor extents, both pHi-gradients were enhanced and both Vmem-gradients were reduced by inhibiting voltage-dependent L-type Ca2+-channels, whereas only both pHi-gradients were reduced (increasing acidification) by inhibiting V-ATPases or NHE and Na+-channels. CONCLUSIONS: Our data show that in the Drosophila follicle-cell epithelium stage-specific pHi- and Vmem-gradients develop which result from the activity of several ion-transport mechanisms. These gradients are supposed to represent important bioelectrical cues during oogenesis, e.g., by serving as electrochemical prepatterns in modifying cell polarity and cytoskeletal organisation.


Asunto(s)
Epitelio/fisiología , Transporte Iónico/fisiología , Folículo Ovárico/citología , Simportadores de Cloruro de Sodio-Potasio/metabolismo , ATPasas de Translocación de Protón Vacuolares/metabolismo , Animales , Membrana Celular/metabolismo , Drosophila melanogaster , Electroquímica , Femenino , Concentración de Iones de Hidrógeno , Potenciales de la Membrana/fisiología , Oogénesis , Canales de Potasio/fisiología , Canales de Sodio/fisiología
14.
PLoS Comput Biol ; 15(5): e1006475, 2019 05.
Artículo en Inglés | MEDLINE | ID: mdl-31059498

RESUMEN

Inferior olivary activity causes both short-term and long-term changes in cerebellar output underlying motor performance and motor learning. Many of its neurons engage in coherent subthreshold oscillations and are extensively coupled via gap junctions. Studies in reduced preparations suggest that these properties promote rhythmic, synchronized output. However, the interaction of these properties with torrential synaptic inputs in awake behaving animals is not well understood. Here we combine electrophysiological recordings in awake mice with a realistic tissue-scale computational model of the inferior olive to study the relative impact of intrinsic and extrinsic mechanisms governing its activity. Our data and model suggest that if subthreshold oscillations are present in the awake state, the period of these oscillations will be transient and variable. Accordingly, by using different temporal patterns of sensory stimulation, we found that complex spike rhythmicity was readily evoked but limited to short intervals of no more than a few hundred milliseconds and that the periodicity of this rhythmic activity was not fixed but dynamically related to the synaptic input to the inferior olive as well as to motor output. In contrast, in the long-term, the average olivary spiking activity was not affected by the strength and duration of the sensory stimulation, while the level of gap junctional coupling determined the stiffness of the rhythmic activity in the olivary network during its dynamic response to sensory modulation. Thus, interactions between intrinsic properties and extrinsic inputs can explain the variations of spiking activity of olivary neurons, providing a temporal framework for the creation of both the short-term and long-term changes in cerebellar output.


Asunto(s)
Potenciales de Acción/fisiología , Núcleo Olivar/fisiología , Animales , Cerebelo/fisiología , Fenómenos Electrofisiológicos , Femenino , Uniones Comunicantes/fisiología , Masculino , Potenciales de la Membrana/fisiología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Neuronas/fisiología , Periodicidad
15.
Endocrinology ; 160(6): 1480-1491, 2019 06 01.
Artículo en Inglés | MEDLINE | ID: mdl-31083714

RESUMEN

A subpopulation of kisspeptin neurons located in the arcuate nucleus (ARN) operate as the GnRH pulse generator. The activity of this population of neurons can be monitored in real-time for long periods using kisspeptin neuron-selective GCaMP6 fiber photometry. Using this approach, we find that ARN kisspeptin neurons exhibit brief (∼50 seconds) periods of synchronized activity that precede pulses of LH in intact female mice. The dynamics and frequency of these synchronization episodes (SEs) are stable at approximately one event every 40 minutes throughout metestrus, diestrus, and proestrus, but slow considerably on estrus to occur approximately once every 10 hours. Evaluation of ARN kisspeptin neuron activity across the light-dark transition, including the time of onset of the proestrus LH surge, revealed no changes in SE frequency. Longer 24-hour recordings across proestrus into estrus demonstrated that an abrupt decrease in SEs occurred ∼4 to 5 hours after the onset of the LH surge to reach the low frequency of SEs observed on estrus. The frequency of SEs was stable across the 24-hour period from metestrus to diestrus. Administration of progesterone to diestrus mice resulted in the abrupt slowing of SEs. These observations show that the GnRH pulse generator exhibits an unvarying pattern of activity from metestrus through to the late evening of proestrus, at which time it slows dramatically, likely in response to postovulation progesterone secretion. The GnRH pulse generator maintains a constant frequency of activity across the time of the LH surge, demonstrating that it is not involved directly in surge generation.


Asunto(s)
Núcleo Arqueado del Hipotálamo/metabolismo , Ciclo Estral/fisiología , Hormona Liberadora de Gonadotropina/metabolismo , Potenciales de la Membrana/fisiología , Neuronas/metabolismo , Animales , Femenino , Kisspeptinas/genética , Kisspeptinas/metabolismo , Hormona Luteinizante/metabolismo , Ratones , Ratones Transgénicos
16.
Neuroscience ; 410: 108-117, 2019 07 01.
Artículo en Inglés | MEDLINE | ID: mdl-31085281

RESUMEN

Opioid prescription and illegal use have been soaring, and it has become a global concern. Adolescence, as a critical developmental period, is radically influenced by drug exposure. In the recent decade, transgenerational effects of paternal environmental exposure have been given greater consideration. There is compelling evidence for the effect of paternal drug abuse such as alcohol, cocaine, and nicotine on the offspring; however, a limited number of studies have focused on the paternal effect of opioids during adolescence on progeny. Locus coeruleus (LC) is a noradrenergic nucleus involved in different brain functions and cognitive processes. The present study aimed to investigate the transgenerational effect of adolescent morphine exposure on electrophysiological properties of LC neurons of the offspring. For this purpose, adolescent male rats received morphine or saline for 10 days between postnatal days 31 and 40, and then after 20 days of washout period, they were mated with naïve female rats. Whole cell patch clamp recordings were performed in current clamp configuration from LC neurons of 14-21-day-old male offspring. The results demonstrated that the decay slope of the action potentials and the amplitude of afterhyperpolarization potential increased in morphine sired animals. Moreover, the duration of action potentials decreased in morphine sired animals. Besides, the coefficient of variation of interspike intervals increased in morphine sired animals compared to the saline sired ones. Overall, the altered electrophysiological properties observed in this study may suggest a functional enhancement of Ca2+ activated K+ channels in LC neurons of morphine sired animals.


Asunto(s)
Analgésicos Opioides/toxicidad , Locus Coeruleus/efectos de los fármacos , Morfina/toxicidad , Neuronas/efectos de los fármacos , Exposición Paterna/efectos adversos , Factores de Edad , Animales , Femenino , Locus Coeruleus/fisiología , Masculino , Potenciales de la Membrana/efectos de los fármacos , Potenciales de la Membrana/fisiología , Neuronas/fisiología , Técnicas de Cultivo de Órganos , Embarazo , Ratas , Ratas Wistar
17.
PLoS One ; 14(5): e0216999, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-31116780

RESUMEN

Organ level simulation of bioelectric behavior in the body benefits from flexible and efficient models of cellular membrane potential. These computational organ and cell models can be used to study the impact of pharmaceutical drugs, test hypotheses, assess risk and for closed-loop validation of medical devices. To move closer to the real-time requirements of this modeling a new flexible Fourier based general membrane potential model, called as a Resonant model, is developed that is computationally inexpensive. The new model accurately reproduces non-linear potential morphologies for a variety of cell types. Specifically, the method is used to model human and rabbit sinoatrial node, human ventricular myocyte and squid giant axon electrophysiology. The Resonant models are validated with experimental data and with other published models. Dynamic changes in biological conditions are modeled with changing model coefficients and this approach enables ionic channel alterations to be captured. The Resonant model is used to simulate entrainment between competing sinoatrial node cells. These models can be easily implemented in low-cost digital hardware and an alternative, resource-efficient implementations of sine and cosine functions are presented and it is shown that a Fourier term is produced with two additions and a binary shift.


Asunto(s)
Potenciales de Acción/fisiología , Potenciales de la Membrana/fisiología , Miocitos Cardíacos/fisiología , Nodo Sinoatrial/fisiopatología , Animales , Electrofisiología Cardíaca , Simulación por Computador , Fenómenos Electrofisiológicos , Electrofisiología , Análisis de Fourier , Frecuencia Cardíaca/fisiología , Humanos , Células Musculares/fisiología , Conejos
18.
Invest Ophthalmol Vis Sci ; 60(6): 2294-2303, 2019 05 01.
Artículo en Inglés | MEDLINE | ID: mdl-31117121

RESUMEN

Purpose: The concentration of protons in the aqueous humor (AH) of the vertebrate eye is maintained close to blood pH; however, pathologic conditions and surgery may shift it by orders of magnitude. We investigated whether and how changes in extra- and intracellular pH affect the physiology and function of trabecular meshwork (TM) cells that regulate AH outflow. Methods: Electrophysiology, in conjunction with pharmacology, gene knockdown, and optical recording, was used to track the pH dependence of transmembrane currents and mechanotransduction in primary and immortalized human TM cells. Results: Extracellular acidification depolarized the resting membrane potential by inhibiting an outward K+-mediated current, whereas alkalinization hyperpolarized the cells and augmented the outward conductance. Intracellular acidification with sodium bicarbonate hyperpolarized TM cells, whereas removal of intracellular protons with ammonium chloride depolarized the membrane potential. The effects of extra- and intracellular acid and alkaline loading were abolished by quinine, a pan-selective inhibitor of two-pore domain potassium (K2P) channels, and suppressed by shRNA-mediated downregulation of the mechanosensitive K2P channel TREK-1. Extracellular acidosis suppressed, whereas alkalosis facilitated, the amplitude of the pressure-evoked TREK-1-mediated outward current. Conclusions: These results demonstrate that TM mechanotransduction mediated by TREK-1 channels is profoundly sensitive to extra- and intracellular pH shifts. Intracellular acidification might modulate aqueous outflow and IOP by stimulating TREK-1 channels.


Asunto(s)
Concentración de Iones de Hidrógeno , Canales de Potasio de Dominio Poro en Tándem/fisiología , Presión , Malla Trabecular/fisiología , Células Cultivadas , Humanos , Mecanotransducción Celular/fisiología , Potenciales de la Membrana/fisiología , Técnicas de Placa-Clamp
19.
Biochim Biophys Acta Mol Cell Res ; 1866(9): 1376-1388, 2019 09.
Artículo en Inglés | MEDLINE | ID: mdl-31136755

RESUMEN

Cargo receptors in the endoplasmic reticulum (ER) recognize and help membrane and soluble proteins along the secretory pathway to reach their location and functional site. We characterized physiological properties of Saccharomyces cerevisiae strains lacking the ERV14 gene, which encodes a cargo receptor part of COPII-coated vesicles that cycles between the ER and Golgi membranes. The lack of Erv14 resulted in larger cell volume, plasma-membrane hyperpolarization, and intracellular pH decrease. Cells lacking ERV14 exhibited increased sensitivity to toxic cationic drugs and decreased ability to grow on low K+. We found no change in the localization of plasma membrane H+-ATPase Pma1, Na+, K+-ATPase Ena1 and K+ importer Trk2 or vacuolar K+-Cl- co-transporter Vhc1 in the absence of Erv14. However, Erv14 influenced the targeting of two K+-specific plasma-membrane transport systems, Tok1 (K+ channel) and Trk1 (K+ importer), that were retained in the ER in erv14Δ cells. The lack of Erv14 resulted in growth phenotypes related to a diminished amount of Trk1 and Tok1 proteins. We confirmed that Rb+ whole-cell uptake via Trk1 is not efficient in cells lacking Erv14. ScErv14 helped to target Trk1 homologues from other yeast species to the S. cerevisiae plasma membrane. The direct interaction between Erv14 and Tok1 or Trk1 was confirmed by co-immunoprecipitation and by a mating-based Split Ubiquitin System. In summary, our results identify Tok1 and Trk1 to be new cargoes for Erv14 and show this receptor to be an important player participating in the maintenance of several physiological parameters of yeast cells.


Asunto(s)
Transporte Biológico/fisiología , Proteínas de Transporte de Catión/metabolismo , Membrana Celular/metabolismo , Potenciales de la Membrana/fisiología , Proteínas de la Membrana/metabolismo , Canales de Potasio/metabolismo , Potasio/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Vesículas Cubiertas por Proteínas de Revestimiento/metabolismo , Proteínas de Transporte de Catión/genética , Tamaño de la Célula , Retículo Endoplásmico/metabolismo , Eliminación de Gen , Regulación Fúngica de la Expresión Génica , Glucosa/metabolismo , Aparato de Golgi/metabolismo , Homeostasis , Concentración de Iones de Hidrógeno , Proteínas de la Membrana/genética , Canales de Potasio/genética , ATPasas de Translocación de Protón/metabolismo , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , Sodio/metabolismo , ATPasa Intercambiadora de Sodio-Potasio/metabolismo , Transcriptoma
20.
J Physiol Sci ; 69(4): 653-660, 2019 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-31087220

RESUMEN

Hypokalemia, an abnormally low level of potassium (K+), is a electrolyte imbalance that commonly occurs in heart failure patients. Hypokalemia is well known to induce lethal ventricular arrhythmia. However, the effects of hypokalemia in failing hearts that have undergone electrophysiological remodeling, i.e., the reactivation of fetal-type ion channels, remain unexplored. We have examined the effect of hypokalemia in the myocytes of transgenic mice overexpressing the hyperpolarization-activated, cyclic nucleotide-sensitive (HCN) channel in the heart (HCN2-Tg mice). Perfusion with a mild hypokalemic solution containing 3 mM K+ induced ectopic ventricular automaticity in 55.0% of HCN2-Tg mouse myocytes. In the remaining HCN2-Tg mouse myocytes, the resting membrane potential (RMP) was more depolarized than that of wild-type myocytes subjected to the same treatment and could also be hyperpolarized by an HCN channel blocker. We conclude that in hypokalemia in our mice model, the HCN2 channel was constitutively activated at the hyperpolarized RMP, thereby destabilizing the electrophysiological activity of ventricular myocytes.


Asunto(s)
Arritmias Cardíacas/metabolismo , Canales Regulados por Nucleótidos Cíclicos Activados por Hiperpolarización/metabolismo , Hipopotasemia/metabolismo , Canales de Potasio/metabolismo , Animales , Insuficiencia Cardíaca/metabolismo , Ventrículos Cardíacos/metabolismo , Potenciales de la Membrana/fisiología , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Miocitos Cardíacos/metabolismo , Potasio/metabolismo
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