Long-term near-continuous recording with Neuropixels probes in healthy and epileptic rats.

Neuropixels probes have become a crucial tool for high-density electrophysiological recordings. Although most research involving these probes is in acute preparations, some scientific inquiries require long-term recordings in freely moving animals. Recent reports have presented prosthesis designs for chronic recordings, but some of them do not allow for probe recovery, which is desirable given their cost.

Deficit in observational learning in experimental epilepsy.

Individuals use the observation of a conspecific to learn new behaviors and skills in many species. Whether observational learning is affected in epilepsy is not known. Using the pilocarpine rat model of epilepsy, we assessed learning by observation in a spatial task.

The circadian dynamics of the hippocampal transcriptome and proteome is altered in experimental temporal lobe epilepsy.

Gene and protein expressions display circadian oscillations, which can be disrupted in diseases in most body organs. Whether these oscillations occur in the healthy hippocampus and whether they are altered in epilepsy are not known. We identified more than 1200 daily oscillating transcripts in the hippocampus of control mice and 1600 in experimental epilepsy, with only one-fourth oscillating in both conditions.

Cell Assemblies in the Cortico-Hippocampal-Reuniens Network during Slow Oscillations.

The nucleus reuniens (NR) is an important anatomic and functional relay between the medial prefrontal cortex (mPFC) and the hippocampus (HPC). Whether the NR controls neuronal assemblies, a hallmark of information exchange between the HPC and mPFC for memory transfer/consolidation, is not known. Using simultaneous local field potential and unit recordings in NR, HPC, and mPFC in male rats during slow oscillations under anesthesia, we identified a reliable sequential activation of NR neurons at the beginning of UP states, which preceded mPFC ones.

GABA-glutamate supramammillary neurons control theta and gamma oscillations in the dentate gyrus during paradoxical (REM) sleep.

Several studies suggest that neurons from the lateral region of the SuM (SuML) innervating the dorsal dentate gyrus (DG) display a dual GABAergic and glutamatergic transmission and are specifically activated during paradoxical (REM) sleep (PS). The objective of the present study is to characterize the anatomical, neurochemical and electrophysiological properties of the SuML-DG projection neurons and to determine how they control DG oscillations and neuronal activation during PS and other vigilance states. For this purpose, we combine structural connectivity techniques using neurotropic viral vectors (rabies virus, AAV), neurochemical anatomy (immunohistochemistry, in situ hybridization) and imaging (light, electron and confocal microscopy) with in vitro (patch clamp) and in vivo (LFP, EEG) optogenetic and electrophysiological recordings performed in transgenic VGLUT2-cre male mice.

Targeted Transgene Expression in Cholinergic Interneurons in the Monkey Striatum Using Canine Adenovirus Serotype 2 Vectors.

The striatum, the main input structure of the basal ganglia, is critical for action selection and adaptive motor control. To understand the neuronal mechanisms underlying these functions, an analysis of microcircuits that compose the striatum is necessary. Among these, cholinergic interneurons (ChIs) provide intrinsic striatal innervation whose dysfunction is implicated in neuropsychiatric diseases, such as Parkinson's disease and Tourette syndrome.

In Vivo Characterization of Neurophysiological Diversity in the Lateral Supramammillary Nucleus during Hippocampal Sharp-wave Ripples of Adult Rats.

The extent of the networks that control the genesis and modulation of hippocampal sharp-wave ripples (SPW-Rs), which are involved in memory consolidation, remains incompletely understood. Here, we performed a detailed in vivo analysis of single cell firing in the lateral supramammillary nucleus (lSuM) during theta and slow oscillations, including SPW-Rs, in anesthetized rats. We classified neurons as SPW-R-active and SPW-R-unchanged according to whether or not they increased their firing during SPW-Rs.

Effects of Single Cage Housing on Stress, Cognitive, and Seizure Parameters in the Rat and Mouse Pilocarpine Models of Epilepsy.

Many experimental approaches require housing rodents in individual cages, including in epilepsy research. However, rats and mice are social animals; and individual housing constitutes a stressful situation. The goal of the present study was to determine the effects of individual housing as compared to conditions maintaining social contact on stress markers and epilepsy.

Electrophoretic drug delivery for seizure control.

The persistence of intractable neurological disorders necessitates novel therapeutic solutions. We demonstrate the utility of direct in situ electrophoretic drug delivery to treat neurological disorders. We present a neural probe incorporating a microfluidic ion pump (μFIP) for on-demand drug delivery and electrodes for recording local neural activity.

A bilayered PVA/PLGA-bioresorbable shuttle to improve the implantation of flexible neural probes.

Objective: Neural electrophysiology is often conducted with traditional, rigid depth probes. The mechanical mismatch between these probes and soft brain tissue is unfavorable for tissue interfacing. Making probes compliant can improve biocompatibility, but as a consequence, they become more difficult to insert into the brain.

The Nucleus Reuniens Controls Long-Range Hippocampo-Prefrontal Gamma Synchronization during Slow Oscillations.

Gamma oscillations are involved in long-range coupling of distant regions that support various cognitive operations. Here we show in adult male rats that synchronized bursts of gamma oscillations bind the hippocampus (HPC) and prefrontal cortex (mPFC) during slow oscillations and slow-wave sleep, a brain state that is central for consolidation of memory traces. These gamma bursts entrained the firing of the local HPC and mPFC neuronal populations.

Neuroinflammation Alters Integrative Properties of Rat Hippocampal Pyramidal Cells.

Neuroinflammation is consistently found in many neurological disorders, but whether or not the inflammatory response independently affects neuronal network properties is poorly understood. Here, we report that intracerebroventricular injection of the prototypical inflammatory molecule lipopolysaccharide (LPS) in rats triggered a strong and long-lasting inflammatory response in hippocampal microglia associated with a concomitant upregulation of Toll-like receptor (TLR4) in pyramidal and hilar neurons. This, in turn, was associated with a significant reduction of the dendritic hyperpolarization-activated cyclic AMP-gated channel type 1 (HCN1) protein level while Kv4.

Autoclave Sterilization of PEDOT:PSS Electrophysiology Devices.

Autoclaving, the most widely available sterilization method, is applied to poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS) electrophysiology devices. The process does not harm morphology or electrical properties, while it effectively kills E. coli intentionally cultured on the devices.

Low β2 Main Peak Frequency in the Electroencephalogram Signs Vulnerability to Depression.

After an intense and repeated stress some rats become vulnerable to depression. This state is characterized by persistent low serum BDNF concentration. Our objective was to determine whether electrophysiological markers can sign vulnerability to depression.

Recovery of brain biomarkers following peroxisome proliferator-activated receptor agonist neuroprotective treatment before ischemic stroke.

Background: Lipid lowering agent such as agonists of peroxisome proliferator-activated receptors (PPAR) are suggested as neuroprotective agents and may protect from the sequelae of brain ischemic stroke. Although the demonstration is not clearly established in human, the underlying molecular mechanism may be of interest for future therapeutic purposes. To this end, we have used our well established rodent model of ischemia-reperfusion pre-treated or not with fenofibrate or atorvastatin and performed a differential proteomics analyses of the brain and analysed the protein markers which levels returned to "normal" following pre-treatments with PPARα agonists.