Elevation of pentylenetetrazole-induced seizure threshold in cholestatic mice: interaction between opioid and cannabinoid systems.

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Elevation of pentylenetetrazole-induced seizure threshold in cholestatic mice: interaction between opioid and cannabinoid systems.

J Gastroenterol Hepatol. 2008 Jul;23(7 Pt 2):e251-7

Authors: Shafaroodi H, Ghasemi M, Dehpour AR

BACKGROUND AND AIM: Several studies have reported that endogenous opioid and cannabinoid systems may be involved in some pathophysiological changes occurring in cholestatic liver disease. It is well known that endogenous opioids and cannabinoids alter the susceptibility of experimental animals to different models of seizure. METHODS: The alterations in pentylenetetrazole-induced clonic seizure thresholds were evaluated from 1 to 6 days after bile duct ligation in mice. Whether the pretreatment of cholestatic mice with different doses of opioid receptor antagonist naltrexone or cannabinoid CB(1) receptor antagonist AM251 (AM251) would have changed the clonic seizure threshold was also examined. RESULTS: Although the clonic seizure threshold was similar between sham-operated and unoperated mice, there was a time-dependent increase in the threshold in cholestatic mice, reaching a peak on day 3 after bile duct ligation and declining partially after day 4. Chronic pretreatment with naltrexone (2, 5, and 10 mg/kg) reversed the increased threshold in cholestatic mice on day 3 after operation in a dose-dependent manner with the highest doses used restoring the threshold to that of the control animals. A similar reversal of the increased threshold was observed after acute (0.5, 0.75, and 1 mg/kg) or chronic (0.5 mg/kg for 4 days) pretreatment with AM251. Moreover, concurrent administration of doses of AM251 and naltrexone that each separately induced a partial reversal of increased seizure threshold in cholestasis caused a complete restoring of the threshold to the control level. CONCLUSIONS: Both opioid and cannabinoid CB(1) receptors may be involved in the dramatic increase in pentylenetetrazole-induced seizure threshold in cholestasis.

PMID: 17764531 [PubMed - indexed for MEDLINE]

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Effects of levetiracetam on generalized discharges monitored with ambulatory EEG in epileptic patients.

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Effects of levetiracetam on generalized discharges monitored with ambulatory EEG in epileptic patients.

Seizure. 2008 Oct 1;

Authors: Pro S, Vicenzini E, Pulitano P, Voti PL, Zarabla A, Randi F, Mecarelli O

PURPOSE: Quantitative analysis of epileptiform discharges (EDs) before and after the initiation of an antiepileptic treatment is a useful tool to objectively documentate the efficacy of an antiepileptic drug (AED). Aim of this study was to evaluate the effect of levetiracetam (LEV) on EDs, monitored with ambulatory EEG (A/EEG), in a limited series of patients with generalized epilepsy. METHODS: We performed 24h A/EEG recording in basal condition and at follow-up after LEV therapy in 21 adult epileptic patients. Eleven received LEV as monotherapy and 10 as add-on. For each patient we quantified total epileptic activity considering the following parameters: total number, total duration, maximal duration and median duration of EDs. Self-reported information on the effect of LEV on clinical seizures was also collected, to determine the electro-clinical correlation. RESULTS: A high variability of the response to LEV was observed in the monotherapy group, without statistical differences for all the parameters investigated. A significant reduction of the total number of seizures (113.6 vs. 41.2; p=.01) was observed in patients in add-on therapy. The modifications of epileptiform EEG abnormalities did not necessarily correlate with the self-reported clinical impressions. DISCUSSION: The quantification of EDs monitored by A/EEG provides a useful objective support for evaluating the neurophysiologic profile and the real efficacy of an antiepileptic treatment. In our patients LEV was able to significantly reduce the EDs only in add-on therapy. Further larger studies are necessary to clarify the effects of LEV on electro-clinical features of generalized epilepsy.

PMID: 18835193 [PubMed - as supplied by publisher]

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Distribution of the olfactory fibre input into the olfactory tubercle of the in vitro isolated guinea pig brain.

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Distribution of the olfactory fibre input into the olfactory tubercle of the in vitro isolated guinea pig brain.

J Neurophysiol. 2008 Oct 15;

Authors: Carriero G, Uva L, Gnatkovsky V, de Curtis M

The olfactory tubercle (OT) is a cortical component of the olfactory system involved in reward mechanisms of drug abuse. This region covers an extensive part of the rostral ventral cerebrum and is relatively poorly investigated. The intrinsic network interactions evoked by olfactory input are here analysed in the OT of the in vitro isolated guinea pig brain by means of field potential analysis and optical imaging of voltage-sensitive signals. Stimulation of the lateral olfactory tract induces a monosynaptic response that progressively decreases in amplitude from lateral to medial. The monosynaptic input induces a disynaptic response that is proportionally larger in the medial portion of the OT. Direct stimulation of the piriform cortex and subsequent lesion of this pathway demonstrated the existence of a prominent associative projection from the anterior part of the piriform cortex to the lateral part of the OT. Optical and electrophysiological recordings of the signals evoked by stimulation of the olfactory tract during arterial perfusion with the voltage-sensitive dye di-2-ANEPEQ confirmed the pattern of distribution of the mono and disynaptic responses in the OT. Finally, current source density analysis of laminar profiles recorded with 16-channel silicon probes confirmed that the monosynaptic and disynaptic potentials localize in the most superficial and the deep portions of the plexiform layer I, as suggested by previous reports. This study sets the standard for further analysis of the modulation of network properties in this largely unexplored brain region.

PMID: 18922946 [PubMed - as supplied by publisher]

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Pavlov's moth: olfactory learning and spike timing-dependent plasticity.

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Pavlov's moth: olfactory learning and spike timing-dependent plasticity.

Nat Neurosci. 2008 Oct;11(10):1126-7

Authors: Meeks JP, Holy TE

PMID: 18818593 [PubMed - indexed for MEDLINE]

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Differential potentiation of early and late components evoked in olfactory cortex by stimulation of cortical association fibers.

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Differential potentiation of early and late components evoked in olfactory cortex by stimulation of cortical association fibers.

Brain Res. 2008 Oct 17;

Authors: Stripling JS, Galupo MP

The present study examined in detail the development and decay of potentiation induced in vivo by repeated high-frequency stimulation of cortical association fibers (AF) in piriform cortex (PC). Male Long-Evans rats with chronically-implanted stimulating and recording electrodes were administered potentiating AF stimulation (thirty 10-pulse 100-Hz trains) on 8 consecutive days, followed by a ninth administration after an 8-day layoff. The time course of potentiation was monitored by local field potentials evoked in the PC and olfactory bulb (OB) by 0.1 Hz single-pulse AF test stimulation before, during, and following each potentiating treatment. AF test stimulation evoked two distinct components in the PC, an early component (EC) and a late component (LC). High-frequency AF stimulation produced potentiation of each component, but with very different characteristics. EC potentiation consisted of a brief augmentation during each bout of potentiating stimulation that persisted <2 min after the last high-frequency train and showed no cumulative effects following repeated induction across days. In contrast, LC potentiation developed gradually, requiring several daily potentiation treatments to reach maximum amplitude, and decayed more slowly each time it was induced. Furthermore, LC potentiation persisted in latent form for at least 8 days following its apparent decay and could be reinstated by repeated test stimulation that was without effect at the beginning of the experiment. Potentiation in the OB resembled LC potentiation in its characteristics, but with less latent potentiation. These results indicate that the potentiation reported here is distinctly different from the long-term potentiation previously demonstrated in vitro in the PC, and suggest that this potentiation represents an increase in excitability within the cortical association fiber system that can be stored in latent form and retrieved at a later time. These characteristics make this potentiation a suitable candidate for participation in long-term functional changes within olfactory cortex.

PMID: 18955033 [PubMed - as supplied by publisher]

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Vote on Graphs « GraphJam: Music and Pop Culture in Charts and Graphs. Let us explain them.

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Why no c*nt and paste for the iPhone? • The Register

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