CHARACTERISTICS OF GAMMA OSCILLATIONS INDUCED BY KAINATE PRESSURE EJECTION ON CA1 HIPPOCAMPUS OF MICE BRAIN SLICES IN SUBMERGED CHAMBERS.

Aim - mostly, gamma oscillations are studied in interface-type chambers. The purpose of the presented investigation is to describe the characteristics of gamma oscillations induced in submerged chambers by kainite pressure ejection. Horizontal combined entorhynal-hippocampal slices 300-350 µm were prepared from young mice (P18-28). Gamma oscillations were induced by 1 mM kainite pressure ejection at the boundary of stratum radiatum and lacunosum-moleculare of area CA1. Field potential recordings were registered from the vicinity of kainite application. Induced CA1 local field potential (LFP) oscillations were brief (7.55±3.77 sec.) and had heterogeneous nature; they could be divided into three epochs: well developed initial part of oscillation, middle part with reduced gamma power and last part of the rhythm with sporadic immergence of sparse (3 to 5) gamma cycles. Generally, initial parts of oscillations had higher amplitude and frequency than the middle part of it. Induction of consecutive gamma oscillations did not depend on the duration of the time intervals between oscillations. Their amplitude was affected by the order of induction but not by time intervals between oscillations. Neither the frequency was affected by the order of induced activities in the same slice. However, comparatively lower frequency oscillations were recorded after long time intervals between gamma activities. Induction of CA1 gamma oscillations in submerged conditions will offer significant experimental advantage, like using patch-clamp techniques to study the mechanism of this activity.