Phenytoin and retinal spreading depression.
Several studies indicate that spreading depression is fundamentally related to seizure marches and to the aura of classical migraine. Moreover, recent investigations call attention to its possible relevance in clinical disturbances associated with brain ischemia, trauma, and hypoglycemia. The anticonvulsant phenytoin has been shown to protect the nervous tissue from the effects of anoxia and ischemia. These properties suggest that phenytoin should be able to counteract spreading depression. Therefore, we investigated its effect on spreading depression elicited by mechanical or chemical (KCl) stimulation, in isolated chick retinas. The results showed that phenytoin: (1) increases the threshold concentration of KCl to initiate the phenomenon; (2) decreases the velocity of propagation of spreading depression; (3) shortens considerably the duration of the slow potential, ionic (K+, Ca2+, Cl-), and volume changes of the extracellular compartment during spreading depression. Possible mechanisms underlying the observed effects are discussed.
Chebabo
S R
SR
Instituto de Biofísica Carlos Chagas Filho, Departamento de Neurobiologia, Cidade Universitária-Ilha do Fundão, Rio de Janeiro, Brazil.
Do Carmo
R J
RJ
D000818:Animals; D002645:Chickens; D013181:Cortical Spreading Depression / Q000187:drug effects* / Q000502:physiology; D004594:Electrophysiology; D009994:Osmolar Concentration; D010672:Phenytoin / Q000494:pharmacology*; D011189:Potassium Chloride / Q000494:pharmacology; D012160:Retina / Q000187:drug effects* / Q000502:physiology
D010672:Phenytoin; D011189:Potassium Chloride