SUMMARY
An cctosylvian spiking focus, induced by topical application of mescaline, brought about changes in nitrogenous compounds not only in the focus but throughout the cerebral cortex.
Prior to the onset of the spiking focus, 2 min after mescaline application, ammonia levels increased significantly in all neocortical areas, especially at the focus and homolateral marginal gyrus; free amide nitrogen decreased and non‐protein nitrogen increased throughout the cortex.
During the development of the focus–at 30 min–the ammonia level still remained high, with a tendency to decrease, and free amide nitrogen was decreased in all neocortical areas.
A decrease in‘protein nitrogen’in marginal gyri, on either side and in lipid nitrogen in the epileptical focus as well as in both marginal gyri was also noted.
SUMMARY
The effects of phenobarbitone on free amino acid changes induced by an epileptogenic focus caused by topical application of mescaline to the neocortex of the cat have been investigated.
Rapid injection of phenobarbitone into the carotid artery after ligation of the common stem of the submaxillary and thyroid arteries suppressed the effect of a mescaline focus on alanine and GABA but not that on glutamic acid.
When the epileptogenic focus was induced in cats previously treated with phenobarbitone by i.m. injections on 4 consecutive days the glutamic acid level no longer decreased but alanine, arginine and GABA values were still low.
These alterations occurred throughout the whole neocortex.
Comparison of ECoG and neurochemical findings showed a concordance between the electrical alterations and the glutamic acid level in the neocortex.
The results indicate that one of the mechanisms of the action of phenobarbitone on the evolution of the focus appears to be an alteration in cortical excitability, manifested especially by preventing a decrease of the glutamic acid level.
RÉSUMÉ
On a étudié les effets de la phàenobarbitone sur les variations des acides aminés libres provoquées par un foyer épileptogàene du àa ľapplication locale de mescaline au néocortex du chat.
Ľinjection rapide de phénobarbitone dans ľartàere carotide apràes ligature du tronc commun des artàeres sous‐maxillaire et thyrodienne ont suppriméľeffet du foyer de mescaline sur ľalanine et GAB A mais non sur ľacide glutamique.
Lorsque le foyer était crée chez des chats préalablement traités, pendant 4 jours consécutifs, par la phénobarbitone en injections i.m., le taux ďacide glutamique ne s'abaissait plus, mais les chiffres ďalanine, ďarginine et de GABA restaient faibles.
Ces variations se produisaient dans tout ľensemble du néocortex.
La comparaison de 1'ECoG et des observations neurochimiques a fait ressortir une concordance entre les modifications électriques et le taux ďacide glutamique dans le néocortex.
Les résultats paraissent indiquer que Fun des mécanismes ďaction de la phénobarbitone sur ľévolution du foyer est un changement de ľexcitabilité corticale, dont la manifestation principale est de s'opposer àa la baisse du taux ďacide glutamique.
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