[P3-14] Deregulated tonic inhibition in the hippocampus of mice model of Angelman syndrome
[Introduction] Angelman syndrome is a neurodevelopmental disorder caused by loss of function of the UBE3A gene encoding a ubiquitin E3 ligase. The authors have recently shown that tonic form of GABAergic inhibition (tonic inhibition) is significantly decreased in the cerebellar granule cells of Ube3a knockout mice, mice model of Angelman syndrome. As a mechanism, we have also illustrated that Ube3a deficiency induces increased expression of the neuronal GABA transporter 1 (GAT1) and decreased GABA levels in the extrasynaptic space. As GAT1 expression is not restricted to the cerebellum, these data suggest that deregulation of tonic inhibition plays an important role in the various symptoms of Angelman syndrome including memory deficits. In this study, we investigated GABAergic function in the hippocampus of Ube3a knockout mice to elucidate the mechanism of memory deficits in Angelman syndrome.
[Methodology] Synaptic and tonic form of GABAergic inhibitions of CA1 hippocampal pyramidal neurons are evaluated using patch-clamp recording in an acutely prepared brain slice of Ube3a knockout mice.
[Results] Strength of tonic inhibition of CA1 hippocampal pyramidal neurons were significantly decreased in Ube3a knockout mice. In contrast, any parameter for synaptic inhibition including amplitude or frequency of Inhibitory post synaptic currents, paired pulse ratio or intracellular Cl- concentration were comparable to those of wild type.
[Conclusions] Tonic inhibition is specifically deregulated in CA1 pyramidal neurons of Angelman syndrome models, which may contribute to the memory impairment of this syndrome. We will seek this possibility by analyzing the effects of hippocampus-specific enhancer for tonic inhibition.
[Methodology] Synaptic and tonic form of GABAergic inhibitions of CA1 hippocampal pyramidal neurons are evaluated using patch-clamp recording in an acutely prepared brain slice of Ube3a knockout mice.
[Results] Strength of tonic inhibition of CA1 hippocampal pyramidal neurons were significantly decreased in Ube3a knockout mice. In contrast, any parameter for synaptic inhibition including amplitude or frequency of Inhibitory post synaptic currents, paired pulse ratio or intracellular Cl- concentration were comparable to those of wild type.
[Conclusions] Tonic inhibition is specifically deregulated in CA1 pyramidal neurons of Angelman syndrome models, which may contribute to the memory impairment of this syndrome. We will seek this possibility by analyzing the effects of hippocampus-specific enhancer for tonic inhibition.