Desflurane selectively suppresses long-latency cortical neuronal response to flash in the rat.

Background: The effect of inhalational anesthetics on sensory-evoked unit activity in the cerebral cortex has been controversial. Desflurane has desirable properties for in vivo neurophysiologic studies, but its effect on cortical neuronal activity and neuronal responsiveness is not known. The authors studied the effect of desflurane on resting and visual evoked unit activity in rat visual cortex in vivo.

Antimalarial therapy selection for quinolone resistance among Escherichia coli in the absence of quinolone exposure, in tropical South America.

Background: Bacterial resistance to antibiotics is thought to develop only in the presence of antibiotic pressure. Here we show evidence to suggest that fluoroquinolone resistance in Escherichia coli has developed in the absence of fluoroquinolone use.

Methods: Over 4 years, outreach clinic attendees in one moderately remote and five very remote villages in rural Guyana were surveyed for the presence of rectal carriage of ciprofloxacin-resistant gram-negative bacilli (GNB).

Burst activation of the cerebral cortex by flash stimuli during isoflurane anesthesia in rats.

Background: The degree of suppression of sensory functions during general anesthesia is controversial. Here, the authors investigated whether discrete flash stimuli induced cortical field potential responses at an isoflurane concentration producing burst suppression and compared the spatiotemporal properties and frequency spectra of flash-induced burst responses with those occurring spontaneously.

Methods: Rats were equipped with multiple epidural and intracortical electrodes to record cortical field potentials in the right hemisphere at several locations along the anterior-posterior axis.

Supraspinal anesthesia: behavioral and electroencephalographic effects of intracerebroventricularly infused pentobarbital, propofol, fentanyl, and midazolam.

Background: Anesthetic endpoints of unconsciousness and immobility result from agent effects on both brain and spinal cord that are difficult to separate during systemic administration. To investigate cerebral mechanism of anesthetic-induced unconsciousness, the authors studied behavioral and electrophysiologic effects of four anesthetics infused intracerebroventricularly to conscious rats. The authors aimed to produce progressively increasing anesthetic depths, indicated by electro-encephalographic synchronization and behavioral change.

Isoflurane disrupts anterio-posterior phase synchronization of flash-induced field potentials in the rat.

Consciousness presumes a set of integrated functions such as sensory processing, attention, and interpretation, and may depend upon both local and long-range phase synchronization of neuronal activity in cerebral cortex. Here we investigated whether volatile anesthetic isoflurane at concentrations that produce loss of consciousness (LOC) disrupts long-range anterio-posterior and local anterior synchronization of neuronal activity in the rat. In six rats, deep electrodes were chronically implanted in the primary visual cortex (V1) and in two areas of the motor cortex (M1 and M2) for recording of intracortical event-related potentials (ERP).

Volatile anesthetics disrupt frontal-posterior recurrent information transfer at gamma frequencies in rat.

We seek to understand neural correlates of anesthetic-induced unconsciousness. We hypothesize that cortical integration of sensory information may underlie conscious perception and may be disrupted by anesthetics. A critical role in frontal-posterior interactions has been proposed, and gamma (20-60 Hz) oscillations have also been assigned an essential role in consciousness.

Volatile anesthetics enhance flash-induced gamma oscillations in rat visual cortex.

Background: The authors sought to understand neural correlates of anesthetic-induced unconsciousness. Cortical gamma oscillations have been associated with neural processes supporting conscious perception, but the effect of general anesthesia on these oscillations is controversial. In this study, the authors examined three volatile anesthetics, halothane, isoflurane, and desflurane, and compared their effects on flash-induced gamma oscillations in terms of equivalent concentrations producing the loss of righting reflex (1 minimum alveolar concentration for the loss of righting [MAC(LR)]).