title: Ethosuximide Affects Paired-Pulse Facilitation in Somatosensory Cortex of WAG\Rij Rats as a Model of Absence Seizure.
abstract: OBJECTIVE
  The interaction between somatosensory cortex and thalamus via a thalamocortical loop is a theory behind induction of absence epilepsy. Inside peri-oral somatosensory (S1po) and primary somatosensory forelimb (S1fl) regions, excitatory and inhibitory systems are not balanced and GABAergic inhibitory synapses seem to play a fundamental role in short-term plasticity alterations.
  
  
  METHODS
  We investigated the effects of Ethosuximide on presynaptic changes by utilizing paired-pulse stimulation that was recorded from somatosensory cortex in 18 WAG\Rij rats during epileptic activity. A twisted tripolar electrode including two stimulating electrodes and one recording electrode was implanted into the S1po and S1FL according to stereotaxic landmarks. Paired-pulses (200 µs, 100-1000 µA, 0.1 Hz) were applied to somatosensory cortex at 50, 100, 400, 500 ms inter-pulse intervals for 50 min period.
  
  
  RESULTS
  The results showed that paired-pulse facilitation was significantly reduced at all intervals in all times, but compared to the control group of epileptic WAG/Rij rats (p<0.05), it was exceptional about the first 10 minutes after the injection. At the intervals of 50 and 100 ms, a remarkable PPD was found in second, third, fourth and fifth 10-min post injection.
  
  
  CONCLUSIONS
  These experiments indicate that Ethosuximide has effects on presynaptic facilitation in somatosensory cortex inhibitory loops by alteration in GABA levels that leads to a markedly diminished PPF in paired-pulse stimulation.
authors.affiliation: Neurosciences Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Ghazaleh
authors.initials: G
authors.lastname: Ghamkhari Nejad
authors.affiliation: Neurosciences Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Parviz
authors.initials: P
authors.lastname: Shahabi
authors.affiliation: Neurosciences Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Mohamad Reza
authors.initials: MR
authors.lastname: Alipoor
authors.affiliation: Department of Physiology, Faculty of Medicine, Urmia University of Medical Sciences, Urmia, Iran.
authors.forename: Firouz
authors.initials: F
authors.lastname: Ghaderi Pakdel
authors.affiliation: Road Traffic Injury Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Asghari
authors.affiliation: Drug Applied Research Center, Tabriz University of Medical Sciences,Tabriz, Iran.
authors.forename: Mina
authors.initials: M
authors.lastname: Sadighi Alvandi
keywords: Absence seizure; Paired-pulse stimulation; Somatosensory cortex; WAG\Rij rat
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