We used voltage-sensitive dye imaging to visualize the distribution of initiation sites of the spontaneous interictal-like spikes (sISs) in @entity35 neocortex, in vivo, induced by @entity1027 or @entity5094 over the exposed cortex. The initiation site was small (approximately 200 microm diam). On average each initiation site initiated 2.0 +/- 0.8 sISs (9 animals, 499 sISs, 251 sites). This is significantly different from that in neocortical slices, where each initiation site initiated 30-100 sISs. The initiation sites were not randomly distributed. The distance between two consecutive sites tended to be either <800 or >1200 microm, suggesting a temporal "suppression annulus" surrounding each initiation site. Within the annulus, the likelihood for initiating the next sIS was reduced. Suppression annulus did not have a noticeable change in the presence of @entity1246 (b) antagonist, suggesting it did not depend on the @entity1246 (b) inhibition. We also applied @entity1027 locally to a spot of 800 x 800 microm(2) for approximately 45 min. During this period approximately 1000 sISs occurred within the spot. @entity1027 or @entity5094 was then applied to the entire craniotomy window. The pretreatment created an obvious cluster of initiation sites. Around this cluster, the suppression annulus became obvious in individual animals. Our results suggest that, in disinhibited cortex, @entity302 were initiated from small sites. The initiation sites may cluster in an area with increased local activity. Surrounding each initiation site there may be a temporal suppression annulus.

Initiation of spontaneous @entity302 in the XXXX neocortex in vivo.

@entity1246 :: ('MESH:D005680', 'Chemical') :: ['GABA'] @entity1027 :: ('MESH:D001640', 'Chemical') :: ['bicuculline', 'Bicuculline'] @entity302 :: ('MESH:D004827', 'Disease') :: ['epileptiform events'] @entity5094 :: ('MESH:D010852', 'Chemical') :: ['picrotoxin'] @entity35 :: ('10116', 'Species') :: ['rat']
@entity35 :: (10116,Species) :: ['rat']
