Posterior hypothalamic theta rhythm: Electrophysiological basis and involvement of glutamatergic receptors.

The posterior hypothalamic area (PHa), including the supramammillary nucleus (SuM) and posterior hypothalamic nuclei, forms a crucial part of the ascending brainstem hippocampal synchronizing pathway, that is involved in the frequency programming and modulation of rhythmic theta activity generated in limbic structures. Recent investigations show that in addition to being a modulator of limbic theta activity, the PHa is capable of producing well-synchronized local theta field potentials by itself. The purpose of this study was to examine the ability of the PHa to generate theta field potentials and accompanying cell discharges in response to glutamatergic stimulation under both in vitro and in vivo conditions.

Lamotrigine Attenuates Neuronal Excitability, Depresses GABA Synaptic Inhibition, and Modulates Theta Rhythms in Rat Hippocampus.

Theta oscillations generated in hippocampal (HPC) and cortical neuronal networks are involved in various aspects of brain function, including sensorimotor integration, movement planning, memory formation and attention. Disruptions of theta rhythms are present in individuals with brain disorders, including epilepsy and Alzheimer's disease. Theta rhythm generation involves a specific interplay between cellular (ion channel) and network (synaptic) mechanisms.

The Role of the Posterior Hypothalamus in the Modulation and Production of Rhythmic Theta Oscillations.

Theta rhythm recorded as an extracellular synchronous field potential is generated in a number of brain sites including the hippocampus. The physiological occurrence of hippocampal theta rhythm is associated with the activation of a number of structures forming the ascending brainstem-hippocampal synchronizing pathway. Experimental evidence indicates that the supramammillary nucleus and posterior hypothalamic nuclei, considered as the posterior hypothalamic area, comprise a critical node of this ascending pathway.

Inhibition of Matrix Metalloproteinase 9 Activity Promotes Synaptogenesis in the Hippocampus.

Information coding in the hippocampus relies on the interplay between various neuronal ensembles. We discovered that the application of a cholinergic agonist, carbachol (Cch), which triggers oscillatory activity in the gamma range, induces the activity of matrix metalloproteinase 9 (MMP-9)-an enzyme necessary for the maintenance of synaptic plasticity. Using electrophysiological recordings in hippocampal organotypic slices, we show that Cch potentiates the frequency of miniature inhibitory and excitatory postsynaptic currents (mIPSCs and mEPSCs, respectively) in CA1 neurons and this effect is MMP-9 dependent.

GSK3β activity alleviates epileptogenesis and limits GluA1 phosphorylation.

Background: Glycogen synthase kinase-3β (GSK3β) is a key regulator of cellular homeostasis. In neurons, GSK3β contributes to the control of neuronal transmission and plasticity, but its role in epilepsy remains to be defined.

Methods: Biochemical and electrophysiological methods were used to assess the role of GSK3β in regulating neuronal transmission and epileptogenesis.

Postnatal Development of the Posterior Hypothalamic Theta Rhythm and Local Cell Discharges in Rat Brain Slices.

Theta rhythms have been recorded from rat brain slices of the posterior hypothalamic area (PHa), including the supramammillary and posterior hypothalamic nuclei. Additionally, in numerous studies theta-related neurons were identified in the PHa according to the classification of Bland and Colom (Progress in Neurobiology, 41, 157-208, 1993). It is currently widely accepted that the PHa contributes to the process of HPC theta frequency programming at least in certain behavioral states.

Is electrical coupling involved in the generation of posterior hypothalamic theta rhythm?

Data obtained in in vitro experiments and urethane anaesthetized animals have revealed that the mechanisms responsible for the generation of hippocampal cholinergic theta rhythm are specifically affected by the administration of broad spectrum gap junctions (GJs) blocker - carbenoxolone (CBX). The aim of this study was to examine the effect of GJs modulation on the production of posterior hypothalamic theta. Specifically, we were interested in evaluating whether CBX could attenuate the theta rhythm recorded from the supramammillary nucleus and posterior hypothalamic nuclei, in both in vitro and in vivo preparations.

Cell discharge correlates of posterior hypothalamic theta rhythm recorded in anesthetized rats and brain slices.

Kowalczyk et al. (Hippocampus 2014; 24:7-20) were probably the first to conduct a systemic study of posterior hypothalamic area (PHa) theta rhythm in anesthetized rats. They demonstrated that local PHa theta field potentials were tail-pinch resistant and could be generated in urethane-anesthetized rats independently of ongoing hippocampal formation theta rhythm.

Use of the CDC autocidal gravid ovitrap to control and prevent outbreaks of Aedes aegypti (Diptera: Culicidae).

Populations ofAedes aegypti (L.) can be managed through reductions in adult mosquito survival, number of offspring produced, or both. Direct adult mortality can be caused by the use of space sprays or residual insecticides to mosquito resting sites, and with a variety of residual insecticide-impregnated surfaces that are being tested, such as curtains, covers for water-storage vessels, bednets, and ovitraps.

[Theta rhythm recorded in the hippocampal formation in vitro].

Theta rhythm is the best synchronized EEG activity that can be recorded in the mammalian brain. Hippocampal formation (HPC) is considered to be the main structure involved in the generation of this activity. Numerous data indicate that theta rhythm is involved in long-term potentiation, spatial learning, spatial navigation, verbal and spatial working memory, REM sleep, locomotor activities, and sensori-motor integration.

Atropine-sensitive theta rhythm in the posterior hypothalamic area: in vivo and in vitro studies.

Theta rhythm is the largest, most prominent, and well-documented electroencephalography activity present in a number of mammals, including humans. Spontaneous theta activity recorded locally in the posterior hypothalamic area (PHa) has never been the subject of detailed studies. The authors have shown that local theta field potentials could be generated in urethane-anesthetized rats in the supramammillary (SuM) nuclei and posterior hypothalamic (PH) nuclei.

Spatiotemporal characterization of mTOR kinase activity following kainic acid induced status epilepticus and analysis of rat brain response to chronic rapamycin treatment.

Mammalian target of rapamycin (mTOR) is a protein kinase that senses nutrient availability, trophic factors support, cellular energy level, cellular stress, and neurotransmitters and adjusts cellular metabolism accordingly. Adequate mTOR activity is needed for development as well as proper physiology of mature neurons. Consequently, changes in mTOR activity are often observed in neuropathology.

Theta-related gating cells in hippocampal formation: in vivo and in vitro study.

In this study we extended our earlier in vitro findings concerning the discovery of a novel type of theta-related cells, which we have termed gating cells. There were two main objectives of our present investigations. The first was to determine the distribution of theta gating cells in the separated CA1 and CA3 generators in three different pharmacological conditions: (i) the presence of a cholinergic agonist-carbachol, (ii) the presence of carbachol and GABA(A) ergic antagonist-bicuculline, (iii) the presence of carbachol and GABA(B) ergic antagonist-2-hydroxysaclofen.

Mosquito vectors of West Nile virus during an epizootic outbreak in Puerto Rico.

The purpose of this investigation was to identify the mosquito (Diptera: Culicidae) vectors of West Nile virus (WNV; family Flaviviridae, genus Flavivirus) during an epizootic WNV outbreak in eastern Puerto Rico in 2007. In June 2006, 12 sentinel chicken pens with five chickens per pen were deployed in six types of habitats: herbaceous wetlands, mangrove forests, deciduous forests, evergreen forests, rural areas, and urban areas. Once WNV seroconversion in chickens was detected in June 2007, we began trapping mosquitoes using Centers for Disease Control and Prevention (CDC) miniature (light/CO2-baited) traps, CMT-20 collapsible mosquito (CO2- and ISCA SkinLure-baited) traps, and CDC gravid (hay infusion-baited) traps.