Disruption of Hippocampal Multisynaptic Networks by General Anesthetics.

Background: Previous studies showed that synaptic transmission is affected by general anesthetics, but an anesthetic dose response in freely moving animals has not been done. The hippocampus provides a neural network for the evaluation of isoflurane and pentobarbital on multisynaptic transmission that is relevant to memory function.

Methods: Male Long-Evans rats were implanted with multichannel and single electrodes in the hippocampus.

The hippocampus participates in a pharmacological rat model of absence seizures.

Objective: Using the gamma-butyrolactone (GBL) model of absence seizures in Long-Evans rats, this study investigated if 2.5-6 Hz paroxysmal discharges (PDs) induced by GBL were synchronized among the thalamocortical system and the hippocampus, and whether inactivation of the hippocampus affected PDs.

Methods: Local field potentials were recorded by chronically implanted depth electrodes in the neocortex (frontal, parietal, visual), ventrolateral thalamus and dorsal hippocampal CA1 area.

Comparison of long-term potentiation (LTP) in the medial (monocular) and lateral (binocular) rat primary visual cortex.

Recent evidence suggests that the primary visual cortex (V1) of rodents expresses surprisingly high levels of plasticity into adulthood. For example, long-term potentiation (LTP) is readily induced in the mature V1 of adult rodents in vivo. Here, adult, urethane-anesthetized rats were used for a detailed characterization of LTP in the pathway between the dorsal lateral geniculate nucleus (dLGN) and ipsilateral V1.

Short-term (2 to 5 h) dark exposure lowers long-term potentiation (LTP) induction threshold in rat primary visual cortex.

Up- and down-regulation of synaptic strength (i.e., long-term potentiation, LTP, long-term depression) is thought to be the primary mechanism mediating experience-dependent plasticity of cortical networks.

Histamine facilitates in vivo thalamocortical long-term potentiation in the mature visual cortex of anesthetized rats.

Recent evidence indicates that the mature central visual system retains a higher degree of plasticity than traditionally assumed. However, little is known regarding the neuromodulatory factors that influence plasticity in the adult primary visual cortex (V1). We investigated the role of histamine, one of the neuromodulators that densely innervate all neocortical fields, in modulating plasticity of V1 by examining thalamocortical long-term potentiation (LTP).

Heterosynaptic facilitation of in vivo thalamocortical long-term potentiation in the adult rat visual cortex by acetylcholine.

Acetylcholine (ACh) plays a permissive role in developmental plasticity of fibers from the lateral geniculate nucleus (LGN) to the primary visual cortex (V1). These fibers remain plastic and express long-term potentiation (LTP) in adult rodents, but it is not known if ACh modulates this form of plasticity in the mature V1. We show that, in anesthetized rats, theta burst stimulation (TBS) of the LGN using 5 or 40 theta cycles produced moderate (approximately 20%) and stronger (approximately 40%) potentiation, respectively, of field postsynaptic potentials recorded in the ipsilateral V1.

Stabilization of thalamo-cortical long-term potentiation by the amygdala: cholinergic and transcription-dependent mechanisms.

Synaptic potentiation allows neurons to enhance excitability and store information for extended time periods. We examined the role of the amygdaloid complex, known to facilitate long-term memory encoding, to influence synaptic strength at thalamo-cortical synapses. In urethane-anaesthetized rats, theta-burst stimulation of the dorsal lateral geniculate nucleus of the thalamus induced early phase (1-2 h) long-term potentiation (LTP) of the field postsynaptic potential (fPSP) recorded in the ipsilateral primary visual cortex.

Histaminergic facilitation of electrocorticographic activation: role of basal forebrain, thalamus, and neocortex.

The neuromodulator histamine plays an important role in the regulation of behavioural state and the neocortical electrocorticogram (ECoG). With the present experiments, we characterized the anatomical targets that mediate the cortical-activating effects of histamine. Urethane-anaesthetized rats displayed continuous large-amplitude, low-frequency oscillations with a maximal spectral power in the delta (0.

Neocortical activation by electrical and chemical stimulation of the rat inferior colliculus: intra-collicular mapping and neuropharmacological characterization.

Classic experiments suggested that the midbrain reticular formation plays an important role in the induction and maintenance of high-frequency, low-amplitude activation of the electrocorticogram (ECoG). However, recent studies have shown that generalized activating systems are not restricted to the reticular formation in that non-reticular brain systems (e.g.