title: Blockage of cortical spreading depression by picrotoxin foci of paroxysmal activity.
abstract: 1 per cent Picrotoxin placed on cortex of rat caused paroxysmal ECoG discharges with concomitant increase in [Ke"] from 3 to 6.7 mM with oscillations corresponding to ictal (maximum) and interictal (minimum) spiking. Invasion of the epileptogenic focus by spreading depression was blocked when the amplitude of oscillations of [Ke+] reached 2.6 mM. Epileptogenic activity induced by topical 10 per cent pentazol caused a less marked increase in [Ke+] (4.6 mM) and did not prevent depression from invading the focal area, but did diminish [Ke+] from the normal of 60 to 70 mM to 39 mM. It is concluded that seizure-induced depolarization  of neural elements in deep cortical layers, though inadequate to trigger spreading depression, does prevent it from spreading, in part by activating the sodium pump.
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism*; D013181:Cortical Spreading Depression / Q000187:drug effects*; D004569:Electroencephalography; D010433:Pentylenetetrazole; D010852:Picrotoxin / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism*; D011189:Potassium Chloride; D051381:Rats; D012640:Seizures / Q000139:chemically induced / Q000378:metabolism*; D014403:Tubocurarine
chemical_list: D010433:Pentylenetetrazole; D010852:Picrotoxin; D011188:Potassium; D011189:Potassium Chloride; D014403:Tubocurarine