Improved understanding of the interaction between state of vigilance (SOV) and seizure onset has therapeutic potential. Six rats received injections of tetanus toxin (TeTX) in the ventral hippocampus that resulted in chronic spontaneous seizures. The distribution of SOV before 486 seizures was analyzed for a total of 19 d of recording. Rapid eye movement sleep (REM) and exploratory wake, both of which express prominent hippocampal theta rhythm, preceded 47 and 34%, for a total of 81%, of all seizures. Nonrapid eye movement sleep (NREM) and nonexploratory wake, neither of which expresses prominent theta, preceded 6.8 and 13% of seizures. We demonstrate that identification of SOV yields significant differentiation of seizure susceptibilities, with the instantaneous seizure rate during REM nearly 10 times higher than baseline and the rate for NREM less than half of baseline. Survival analysis indicated a shorter duration of preseizure REM bouts, with a maximum transition to seizure at ϳ90 s after the onset of REM. This study provides the first analysis of a correlation between SOV and seizure onset in the TeTX model of temporal lobe epilepsy, as well as the first demonstration that hippocampal theta rhythms associated with natural behavioral states can serve a seizure-promoting role. Our findings are in contrast with previous studies suggesting that the correlations between SOV and seizures are primarily governed by circadian oscillations and the notion that hippocampal theta rhythms inhibit seizures. The documentation of significant SOV-dependent seizure susceptibilities indicates the potential utility of SOV and its time course in seizure prediction and control.

This study sought to determine the role of the transcription factor E2F1 in CXCR4-mediated neurotoxicity and HIV neuropathology. We studied the effect of the HIV envelope protein gp120 on the expression of E2F1-dependent apoptotic proteins in human and rodent neurons and examined the expression pattern of E2F1 in the brain of HIVinfected individuals. Our findings suggest that in cultured neurons gp120 increased E2F1 levels in the nucleus, stimulated its transcriptional activity and enhanced the expression of the E2F1 target proteins Cdc2 and Puma. Studies with neuronal cultures from E2F1 deficient mice demonstrated that the transcription factor is required for gp120-induced neurotoxicity and up-regulation of Cdc2 and Puma. Levels of E2F1 protein were greater in the nucleus of neurons in brains of HIVinfected patients exhibiting dementia when compared to HIV-negative subjects or HIV-positive neurologically normal patients. Overall, these studies indicate that E2F1 is primarily involved in CXCR4-mediated neurotoxicity and HIV neuropathogenesis.

Potassium fluxes integrate mitochondria into cellular activities, controlling their volume homeostasis and structural integrity in many pathophysiological mechanisms. The outer mitochondrial membrane (OMM) is thought to play a passive role in this process because K ؉ is believed to equilibrate freely between the cytosol and mitochondrial intermembrane space. By patch clamping mitochondria isolated from the central nervous systems of adult mitoCFP transgenic mice, we discovered the existence of I OMMKi , a novel voltage-dependent inwardly rectifying K ؉ conductance located in the OMM. I OMMKi is regulated by osmolarity, potentiated by cAMP, and activated at physiological negative potentials, allowing K ؉ to enter the mitochondrial intermembrane space in a controlled regulated fashion. The identification of I OMMKi in the OMM supports the notion that a membrane potential could exist across this membrane in vivo and suggests that the OMM possesses regulated pathways for K ؉ uptake.Potassium accumulation in mitochondria is known to be regulated by a uniport mechanism that controls mitochondrial volume homeostasis and bioenergetics (1) and works concurrently with a K ϩ -H ϩ exchanger to prevent mitochondrial swelling (2, 3). In particular, K ϩ entry into mitochondria has been credited to its passive diffusion through the outer mitochondrial membrane (OMM) 5 into the intermembrane compartment and to the K ϩ uniport mechanism, which comprises distinct channels located in the inner mitochondrial membrane (IMM) that allow K ϩ to flow into the matrix (4). In contrast to the vast literature on K ϩ currents through the IMM (4 -6), there have been only a few early attempts to study the electrophysiological properties of the OMM in situ (i.e. in intact isolated mitochondria), which fell short of giving a clear picture of K ϩ across this membrane (7). For instance, the large voltagedependent anion channel (VDAC) of the outer membrane was thoroughly described in reconstituted membrane lipid bilayers (8), but it has never been observed or its biophysical features described in patch-clamp experiments of intact mitochondria. Rather, a variety of conductances in the range of 10 -307 picosiemens (in 150 KCl) have been reported (9, 10), whose function and regulation still await to be assigned (5).To provide an additional contribution to the existing database on OMM conductances, we applied the patch-clamp technique to intact mitochondria isolated from the central nervous system of adult mice. This is a severe technical challenge mainly because of the small size of the organelle (ϳ1 m in diameter) and the difficulty in identifying the single mitochondrion in isolation. We circumvented these problems by using tissue homogenization in combination with a bland trypsin treatment and Percoll gradient purification to isolate single neuronal mitochondria from the spinal cord of a transgenic mouse in which a cyan fluorescent protein (CFP) was fused to a mitochondrial transport sequence derived from cytochrome c and expressed in neurons unde...

The role of the brainstem cholinergic system in the regulation of sleep-wake states has been studied extensively but relatively little is known about the role of cholinergic mechanisms in prefrontal cortex in the regulation of sleep-wake states. In a recent study, we showed that prefrontal cholinergic stimulation in anesthetized rat can reverse the traits associated with anesthesia and restore a wake-like state, thereby providing evidence for a causal role for prefrontal cholinergic mechanisms in modulating level of arousal. However, the effect of increase in prefrontal cholinergic tone on spontaneous sleep-wake states has yet to be demonstrated. Therefore, in this study, we tested the hypothesis that delivery of cholinergic agonists – carbachol or nicotine – into prefrontal cortex of rat during slow wave sleep (SWS) would produce behavioral arousal and increase the time spent in wake state. We show that unilateral microinjection (200 nL) of carbachol (1 mM) or nicotine (100 mM) into prefrontal cortex during SWS decreased the latency to the onset of wake state (p = 0.03 for carbachol, p = 0.03 for nicotine) and increased the latency to the onset of rapid eye movement sleep (p = 0.008 for carbachol, p = 0.006 for nicotine). Although the infusion of 1 mM carbachol increased the time spent in wake state (p = 0.01) and decreased the time spent in SWS (p = 0.01), infusion of 10 or 100 mM nicotine did not produce any statistically significant change in sleep-wake architecture. These data demonstrate a differential role of prefrontal cholinergic receptors in modulating spontaneous sleep-wake states.