Calcium Imaging in Brain Tissue Slices.

Calcium imaging is a method that was first developed in the mid-1970s yet kept developing until current days to allow accurate measurement of free calcium ions in tissues. This widely used method has provided significant advances to our understanding of cellular signal transduction, including the discovery of subcellular compartmentalization of neurons and astrocytes, the identification of multiple signaling pathways, and mapping the functional connectivity between astrocytes and neuronal networks. Here we describe a method for the loading and imaging of cell-permeable AM ester calcium-sensitive dyes for the in vitro measurement of free intracellular Ca ions in acute brain slices.

Transformer-based light-evoked retinal spiking activity prediction.

Retinal visual prosthetic devices aim to restore vision via electrical stimulation delivered on the retina. While a number of devices have been commercially available, the stimulation strategies applied have not met the expectations of end-users. These stimulation strategies involve the neurons being activated based on their spatial properties, regardless of their functions, which may lead to lower visual acuity.

Selective neuromodulation of retinal ganglion cells via a hybrid optic-nerve and retinal neuroprosthesis for visual restoration.

A visual neuroprosthesis delivers electrical stimulation to the surviving neural cells of the visual pathway to produce prosthetic vision. While the retina is often chosen as the stimulation site, current retinal prostheses are hindered by the lack of functional selectivity that impairs the resolution. A possible strategy to improve the resolution is to combine the retinal stimulation and the stimulation of the optic nerve bundle, which contains myelinated fibres of retinal ganglion cells (RGCs) axons that vary in diameter.

Overcoming Facial Paralysis with an Implantable Actuator for Restoration of Blink.

The loss of the ability to blink the eyelid is considered the most severe effect of facial nerve paralysis. The delicate homeostasis of the eye is disrupted, and without frequent intervention, the cornea can become damaged, ultimately resulting in blindness. The psychosocial impact is also significant, with individuals withdrawing from society to hide what they perceive to be a disfigurement.

Computational Modeling of Retinal Neurons for Visual Prosthesis Research - Fundamental Approaches.

Computational modeling has become an increasingly important method in neural engineering due to its capacity to predict behaviors of in vivo and in vitro systems. This has the key advantage of minimizing the number of animals required in a given study by providing an often very precise prediction of physiological outcomes. In the field of visual prosthesis, computational modeling has an array of practical applications, including informing the design of an implantable electrode array and prediction of visual percepts that may be elicited through the delivery of electrical impulses from the said array.

Neuron-specific responses to acetylcholine within the spinal dorsal horn circuits of rodent and primate.

Excitatory and inhibitory neurotransmission within the spinal dorsal horn is tightly controlled to regulate transmission of nociceptive signals to the brain. One aspect of this control is modulation of neuronal activity through cholinergic signaling. Nociceptive neurons in the dorsal horn express both nicotinic and muscarinic cholinergic receptors and activation of these receptors reduces pain in humans, while inhibition leads to nociceptive hypersensitivity.

Neuromodulation of Astrocytic K Clearance.

Potassium homeostasis is fundamental for brain function. Therefore, effective removal of excessive K+ from the synaptic cleft during neuronal activity is paramount. Astrocytes play a key role in K+ clearance from the extracellular milieu using various mechanisms, including uptake via Kir channels and the Na-K ATPase, and spatial buffering through the astrocytic gap-junction coupled network.

Method for Prolonged Incubation of Brain Slices.

Slices of neuronal tissue maintain a high degree of topographical and functional properties of neurons and glia and therefore are extensively used for measurements of neuronal activity at the molecular, cellular and network levels. However, the lifespan of slice preparations is narrow, averaging of 6-8 hours. Moreover, the average viability of brain slices varies according to animal age and region of interest, leading to the high variability and low reproducibility of recorded data.

The differential impact of acute microglia activation on the excitability of cholinergic neurons in the mouse medial septum.

The medial septal nucleus is one of the basal forebrain nuclei that projects cholinergic input to the hippocampus and cortex. Two of the hallmarks of Alzheimer's disease (AD) are a significant loss of cholinergic transmission and neuroinflammation, and it has been suggested that these two hallmarks are causally linked to the medial septum. Therefore, we have investigated the age-related susceptibility of medial septal cholinergic neurons to glial activation, mediated via peripheral administration of lipopolysaccharide (500 μg/kg) into ChAT(BAC)-eGFP mice at different ages (3-22 months).

Dynamic interplay between H-current and M-current controls motoneuron hyperexcitability in amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is a type of motor neuron disease (MND) in which humans lose motor functions due to progressive loss of motoneurons in the cortex, brainstem, and spinal cord. In patients and in animal models of MND it has been observed that there is a change in the properties of motoneurons, termed neuronal hyperexcitability, which is an exaggerated response of the neurons to a stimulus. Previous studies suggested neuronal excitability is one of the leading causes for neuronal loss, however the factors that instigate excitability in neurons over the course of disease onset and progression are not well understood, as these studies have looked mainly at embryonic or early postnatal stages (pre-symptomatic).

Extensive astrocyte synchronization advances neuronal coupling in slow wave activity in vivo.

Slow wave activity (SWA) is a characteristic brain oscillation in sleep and quiet wakefulness. Although the cell types contributing to SWA genesis are not yet identified, the principal role of neurons in the emergence of this essential cognitive mechanism has not been questioned. To address the possibility of astrocytic involvement in SWA, we used a transgenic rat line expressing a calcium sensitive fluorescent protein in both astrocytes and interneurons and simultaneously imaged astrocytic and neuronal activity in vivo.

Prolonged Incubation of Acute Neuronal Tissue for Electrophysiology and Calcium-imaging.

Acute neuronal tissue preparations, brain slices and retinal wholemount, can usually only be maintained for 6 - 8 h following dissection. This limits the experimental time, and increases the number of animals that are utilized per study. This limitation specifically impacts protocols such as calcium imaging that require prolonged pre-incubation with bath-applied dyes.

Astrocytic modulation of neuronal excitability through K spatial buffering.

The human brain contains two major cell populations, neurons and glia. While neurons are electrically excitable and capable of discharging short voltage pulses known as action potentials, glial cells are not. However, astrocytes, the prevailing subtype of glia in the cortex, are highly connected and can modulate the excitability of neurons by changing the concentration of potassium ions in the extracellular environment, a process called K clearance.

Calcium Imaging of AM Dyes Following Prolonged Incubation in Acute Neuronal Tissue.

Calcium-imaging is a sensitive method for monitoring calcium dynamics during neuronal activity. As intracellular calcium concentration is correlated to physiological and pathophysiological activity of neurons, calcium imaging with fluorescent indicators is one of the most commonly used techniques in neuroscience today. Current methodologies for loading calcium dyes into the tissue require prolonged incubation time (45-150 min), in addition to dissection and recovery time after the slicing procedure.

Straightforward and effective synthesis of γ-aminobutyric acid transporter subtype 2-selective acyl-substituted azaspiro[4.5]decanes.

Supply of major metabolites such as γ-aminobutyric acid (GABA), β-alanine and taurine is an essential instrument that shapes signalling, proper cell functioning and survival in the brain and peripheral organs. This background motivates the synthesis of novel classes of compounds regulating their selective transport through various fluid-organ barriers via the low-affinity γ-aminobutyric acid (GABA) transporter subtype 2 (GAT2). Natural and synthetic spirocyclic compounds or therapeutics with a range of structures and biological activity are increasingly recognised in this regard.

Recurrent seizure-like events are associated with coupled astroglial synchronization.

Increasing evidence suggest that astrocytes significantly modulate neuronal function at the level of the tripartite synapse both in physiological and pathophysiological conditions. The global control of the astrocytic syncytium over neuronal networks, however, is still less recognized. Here we examined astrocytic signaling during epileptiform activity which is generally attributed to large-scale neuronal synchronization.

Statins alter the hepatobiliary transport of unconjugated and conjugated bilirubin in sandwich-cultured rat hepatocytes.

Several studies have reported that statins occasionally cause impairment of liver functions characterized by elevated serum bilirubin levels, which might be due to altered function of the multidrug resistance-associated proteins (Mrp2/3). We aimed to study the modulation of the hepatobiliary transport of bilirubin by four statin derivatives, atorvastatin, fluvastatin, pravastatin, and rosuvastatin in sandwich-cultured rat hepatocytes. All statins except pravastatin significantly inhibited the uptake of bilirubin.

Ligand-specific regulation of the endogenous mu-opioid receptor by chronic treatment with mu-opioid peptide agonists.

Since the discovery of the endomorphins (EM), the postulated endogenous peptide agonists of the mu-opioid receptors, several analogues have been synthesized to improve their binding and pharmacological profiles. We have shown previously that a new analogue, cis-1S,2R-aminocyclohexanecarboxylic acid(2)-endomorphin-2 (ACHC-EM2), had elevated mu-receptor affinity, selectivity, and proteolytic stability over the parent compound. In the present work, we have studied its antinociceptive effects and receptor regulatory processes.

Lack of regulatory changes of µ-opioid receptors by 14-methoxymetopon treatment in rat brain. Further evidence for functional selectivity.

Here we have studied regulatory changes of µ-opioid receptors accompanying in vivo 14-methoxymetopon treatments of rats. Previously, this ligand has been shown to be an extremely potent, centrally acting µ-opioid specific analgesic with low physical dependence, tolerance, respiratory depression, constipation and other side effects. Our work shows that it is a highly potent full agonist of µ-opioid receptor coupled G-protein signaling in vitro, alike the well-known opioid agonist, etorphine.

Astrocytes convert network excitation to tonic inhibition of neurons.

Background: Glutamate and γ-aminobutyric acid (GABA) transporters play important roles in balancing excitatory and inhibitory signals in the brain. Increasing evidence suggest that they may act concertedly to regulate extracellular levels of the neurotransmitters.

Results: Here we present evidence that glutamate uptake-induced release of GABA from astrocytes has a direct impact on the excitability of pyramidal neurons in the hippocampus.

Assessing toxicity of polyamidoamine dendrimers by neuronal signaling functions.

We report for the first time on neuronal signaling for the evaluation of interactions between native plasmamembrane and polyamidoamine (PAMAM) dendrimers. Generation 5 polycationic (G5-NH(2)), novel β-D-glucopyranose-conjugated G5-NH(2) and generation 4.5 polyanionic (G4.

Long-lasting, distinct changes in central opioid receptor and urinary bladder functions in models of schizophrenia in rats.

Ketamine treatments and social isolation of rats reflect certain features of schizophrenia, among them altered pain sensitivity. To study the underlying mechanisms of these phenomena, rats were either housed individually or grouped for 33 days after weaning, and treated with either ketamine or saline for 14 days. After one month re-socialization, the urinary bladder capacity by ultrasound examination in the anesthetized animals, and changes of μ-opioid receptors by saturation binding experiments using a specific μ-opioid agonist [(3)H]DAMGO were determined.