Lack of respiratory coupling with neocortical and hippocampal slow oscillations.

Previous work has demonstrated an influence of the respiratory cycle and, more specifically, rhythmic nasal inspiration for the entrainment of slow oscillations in olfactory cortex during ketamine-xylazine anesthesia. This respiratory entrainment has been suggested to occur more broadly during slow-wave states (including sleep) throughout the forebrain, in particular in the frontal and parahippocampal and hippocampal cortices. Using multisite local field potential recording methods and spectral coherence analysis in the rat, we show here that no such broad forebrain coupling takes place during slow-wave activity patterns under either ketamine-xylazine or urethane anesthesia and, furthermore, that it also does not arise during natural slow-wave sleep.

A comparison of sleeplike slow oscillations in the hippocampus under ketamine and urethane anesthesia.

During sleep and anesthesia, a slow ( View Article and Find Full Text PDF

Immunohistochemical characterization of substance P receptor (NK(1)R)-expressing interneurons in the entorhinal cortex.

It has been reported that application of substance P (SP) to the medial portion of the entorhinal cortex (EC) induces a powerful antiepileptic effect (Maubach et al. [1998] Neuroscience 83:1047-1062). This effect is presumably mediated via inhibitory interneurons expressing the neurokinin-1 receptor (NK(1)R), but the existence of NK(1)R-expressing inhibitory interneurons in the EC has not yet been reported.

Hippocampal slow oscillation: a novel EEG state and its coordination with ongoing neocortical activity.

State-dependent EEG in the hippocampus (HPC) has traditionally been divided into two activity patterns: theta, a large-amplitude, regular oscillation with a bandwidth of 3-12 Hz, and large-amplitude irregular activity (LIA), a less regular signal with broadband characteristics. Both of these activity patterns have been linked to the memory functions subserved by the HPC. Here we describe, using extracellular field recording techniques in naturally sleeping and urethane-anesthetized rats, a novel state present during deactivated stages of sleep and anesthesia that is characterized by a prominent large-amplitude and slow frequency (< or =1 Hz) rhythm.