Gamma-aminobutyric acid (GABA)ergic mechanisms of the novel antiepileptic drug, levetiracetam (Keppra), have been both favored and rejected. Since paired-pulse interaction is accepted in functionally assessing GABAergic mechanisms, we investigated whether levetiracetam affects the paired-pulse inhibition/facilitation of the field potentials, evoked in the dentate gyrus of urethane-anesthesized rats. This model revealed a strong paired-pulse inhibition at 20-ms interstimulus interval, a noteworthy paired-pulse facilitation at 80-ms interstimulus interval, and a moderate paired-pulse inhibition at 500-ms interstimulus interval. Bicuculline (3 mg/kg/h, i.v.) and baclofen (10 mg/kg, i.v.) markedly depressed paired-pulse inhibition at 20-ms interstimulus interval, while clonazepam (1 mg/kg, i.p.), diazepam (10 mg/kg, i.v.), and phenobarbital (40 mg/kg, i.v.) enhanced it. Bicuculline also depressed paired-pulse inhibition at 500-ms interstimulus interval. Bicuculline, baclofen, and diazepam reduced paired-pulse facilitation at 80-ms interstimulus interval. Distinct from these GABA(A) receptor- and GABA(B) receptor-related drugs, levetiracetam (17 and 540 mg/kg, i.v.) had no significant effect on either paired-pulse interaction in this model, a result not favoring any major role of GABAergic mechanisms in its antiseizure action.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1016/s0014-2999(03)01563-2 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
N1 facilitation at short Inter-Stimulus-Interval (ISI) occurs under 400 ms and is dependent on ISI from previous sounds: Evidence using an unpredictable auditory stimulation sequence.
Int J Psychophysiol
December 2024
Clinical Neurophysiology Research Laboratory, Western Psychiatric Hospital, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
The N1 auditory evoked potential amplitude depends heavily on the inter-stimulus interval (ISI). Typically, shorter ISIs result in reduced N1 amplitudes, suggesting a decreased neural response with high stimulus presentation rates. However, an exception known as N1 facilitation occurs with very brief ISIs (∼150-500 ms), where the N1 amplitude increases.
View Article and Find Full Text PDFSpinally targeted paired associated stimulation with high-frequency peripheral component induces spinal level plasticity in healthy subjects.
Sci Rep
December 2024
BioMag Laboratory, HUS Diagnostic Center, Helsinki University Hospital, University of Helsinki and Aalto University School of Science, Helsinki, Finland.
Article Synopsis
- A new technique called high-PAS combines high-frequency peripheral nerve stimulation (PNS) and high-intensity transcranial magnetic stimulation (TMS) to potentially enhance motor function in patients with incomplete spinal cord injuries.
- The interstimulus interval (ISI) in high-PAS allows for flexibility, making it easier to implement in clinical settings where precise timing is tough, but this also creates challenges for measuring its effectiveness.
- Research with ten healthy participants showed that high-PAS improved motor-evoked potentials (MEPs) and significantly increased spinal excitability (measured by H-reflex amplitudes) during spinal-targeted sessions, but not in cortical-targeted sessions.
Differential effects of stimulation waveform and intensity on the neural structures activated by lumbar transcutaneous spinal cord stimulation.
J Neurophysiol
December 2024
Spinal Cord Injury Research Centre, Neuroscience Research Australia, Randwick, 2031 NSW, Australia.
Introduction: Lumbar transcutaneous spinal cord stimulation (TSS) evokes synchronized muscle responses, termed spinally evoked motor response (sEMR). Whether the structures TSS activates to evoke sEMRs differ when TSS intensity and waveform are varied is unknown.
Methods: In 15 participants (9F:6M), sEMRs were evoked by TSS over L1-L3 (at sEMR threshold and suprathreshold intensities) using conventional (one 400-µs biphasic pulse) or high-frequency burst (ten 40-µs biphasic pulses at 10 kHz) stimulus waveforms in vastus medialis (VM), tibialis anterior (TA) and medial gastrocnemius (MG) muscles.
Factors Influencing Stream Segregation Based on Interaural Phase Difference Cues.
Trends Hear
December 2024
School of Psychology, Aston University, Birmingham, UK.
Interaural time differences are often considered a weak cue for stream segregation. We investigated this claim with headphone-presented pure tones differing in a related form of interaural configuration-interaural phase differences (ΔIPD)-or/and in frequency (ΔF). In experiment 1, sequences comprised 5 × ABA- repetitions (A and B = 80-ms tones, "-" = 160-ms silence), and listeners reported whether integration or segregation was heard.
View Article and Find Full Text PDFNeurophysiological assessment of cortical motor function: A direct comparison of methodologies.
Clin Neurophysiol
December 2024
Neuroscience Research Australia, 139 Barker Street, Randwick, 2031, Sydney, Australia; University of NSW and Department of Neurology, Prince of Wales Hospital, South Eastern Sydney Area Health Service, Sydney, Australia.
Objective: Assessment of cortical function with threshold tracking transcranial magnetic stimulation (TT-TMS) has developed as a biomarker to inform disease pathophysiology, particularly in neurodegenerative disease and dementia. At present, a fully integrated testing system does not exist. To advance clinical utility, and to streamline software design to integrate with diagnostic approaches in an outpatient setting, the present series of studies assessed the effects of altering diagnostic paradigms to measure interstimulus interval (ISI) including serial ascending [T-SICIs] and parallel [T-SICIp] methodologies as measures of cortical motor function (the MagXite software).
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!