Region-dependent regulation of acute ethanol on γ oscillation in the rat hippocampal slices.

Abstract

Ethanol use disorders are a serious medical and public health problem in the world today. Acute ethanol intoxication can lead to cognitive dysfunction such as learning and memory impairment. Gamma oscillations (γ, 30-80Hz) are synchronized rhythmic activity generated by population of neurons within local network, and closely related to learning and memory function. The hippocampus is a critical anatomic structure that supports learning and memory. On the grounds of structure and function, hippocampus can be divided into the intermediate (IH), the dorsal (DH), and ventral hippocampus (VH). The current study is the first to investigate the effects of acute ethanol on γ oscillations in these sub-regions of rat hippocampal slices. The sustained γ oscillations were induced by 200nM kainate (KA) in the CA3c of IH, DH, and VH. When KA-induced γ oscillation reached the steady state, ethanol (50mM or 100mM) was applied and the effects of ethanol on γ oscillation power was measured in the slices sequentially sectioned from ventral to dorsal hippocampus of adult rats. In the intermediate hippocampal slices, compared with control (KA only), ethanol (50mM) caused 36.1 ± 3.9% decrease in γ power (p < 0.05, n = 10), while ethanol (100mM) caused 55.3 ± 5.5% decrease in γ power (p < 0.001, n = 14). In the dorsal hippocampus, only ethanol (100mM) caused 18.1 ± 8.6% decrease in γ power (p < 0.05, n = 12). However, in the ventral hippocampus, neither 50mM nor 100mM ethanol affected γ oscillation. Our results demonstrate that ethanol may produce the differential suppression of γ oscillations in a dose-dependent manner in different sub-regions of hippocampus, suggesting that the modulation of ethanol on hippocampal γ oscillation is region-dependent.