Effects of GABAmimetics on electrocorticographic spike discharges induced by guanidinoethanesulfonic acid (amidino-taurine) in the rat.
The effect of guanidinoethanesulfonic acid (GES) on rat electrocorticograms (ECoG) and the effects of gamma-aminobutyric acid (GABA) and GABA-agonists on the ECoG changes induced by GES were studied. Sporadic spike discharges began 2-5 min after 1 mumol GES/10 microliters on filter paper was applied to the pia mater of the left sensorimotor cortex; spike discharges extended to the opposite cerebral hemisphere 60 min after the onset of the ipsilateral spike discharges. The spike discharges with a frequency of 5-10 spikes/min lasted until the end of the 4 hour recording. The induced spike discharges were suppressed when the original GES soaked filter paper was replaced by one containing GES (1 mumol) supplement combined with taurine (1 mumol/10 microliters). GABA (1 mumol) and its receptor agonist, muscimol (10 nmol) and (3R)-(-)-4-amino-3-hydroxybutyric acid (1 mumol) also suppressed the GES-induced spike discharges when applied topically. Diazepam (DZP) (10 mg/kg) suppressed the GES-induced spike discharges 10 min after i.p. injection, but phenobarbital (20 mg/kg) increased the frequency and voltage of spike discharges 100 min following subcutaneous administration. Intraperitoneal injection of either valproate (200 mg/kg) or phenytoin (25 mg/kg), after the completion of the spike discharges, showed no effect. These findings suggest that neurotransmission or neuromodulatory effects of taurine participate in GES-induced seizure activity, and that GABAA and DZP receptors may play a role in the mechanism that suppresses GES-induced seizures.
Yokoi
I
I
Department of Neuroscience, Okayama University Medical School, Japan.
Kabuto
H
H
Mori
A
A
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects / Q000502:physiology*; D003975:Diazepam / Q000494:pharmacology; D004569:Electroencephalography; D008297:Male; D009118:Muscimol / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013654:Taurine / Q000031:analogs & derivatives* / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D013654:Taurine; D009118:Muscimol; C009558:taurocyamine; D005680:gamma-Aminobutyric Acid; D003975:Diazepam