Impact of S100B on local field potential patterns in anesthetized and kainic acid‐induced seizure conditions in vivo

Abstract

S100B is a calcium-binding protein predominantly expressed in astrocytes. Previous studies using gene-manipulated animals have suggested that the protein has a role in synaptic plasticity and learning. In order to assess the physiological roles of the protein in active neural circuitry, we recorded spontaneous neural activities from various layers of the neocortex and hippocampus in urethane-anesthetized S100B knockout (KO) and wildtype (WT) control mice. Typical local field oscillation patterns including the slow (0.5-2 Hz) oscillations in the neocortex, theta (3-8 Hz) and sharp wave-associated ripple (120-180 Hz) oscillations in the hippocampus were observed in both genotypes. Comparisons of the frequency, power and peak amplitude have shown that these oscillatory patterns were virtually indistinguishable between WT and KO. When seizure was induced by intraperitoneal injection of kainic acid, a difference between WT and KO appeared in the CA1 radiatum local field potential pattern, where seizure events were characterized by prominent appearance of hyper-synchronous gamma band (30-80 Hz) activity. Although both genotypes developed seizures within 40 min, the gamma amplitude was significantly smaller during the development of seizures in KO mice. Our results suggest that deficiency of S100B does not have a profound impact on spontaneous neural activity in normal conditions. However, when neural activity was sufficiently raised, activation of S100B-related pathways may take effect, resulting in modulation of neural activities.

Neural-Activity-Dependent Release of S100B from Astrocytes Enhances Kainate-Induced Gamma OscillationsIn Vivo

“…In agreement with our previous study (Sakatani et al, 2007), the gamma oscillations in hippocampal CA1 stratum radiatum started to develop in 10 min after the administration of KA. The amplitude of the gamma oscillations was significantly smaller in S100B(Ϫ/Ϫ) animals at 45 min after KA injection than that in WT mice [WT, n ϭ 9; S100B(Ϫ/Ϫ), n ϭ 11; gamma amplitude, PBS infusion period before KA injection, p ϭ 0.12; 45 min after KA injection, p Ͻ 0.01] (Fig.…”

“…As the gamma oscillation reduction is most pronounced in stratum radiatum (Sakatani et al, 2007), and glutamate is the major transmitter in stratum radiatum, we asked a possible influence of mGluR3 activation, which has been previously reported to play a role in S100B release in dissociated astrocyte culture (Ciccarelli et al, 1999). Our data further confirm the significant role of mGluR3 activation in S100B release in preserved neuronglia circuitry.…”

“…KA-induced gamma oscillation amplitude is attenuated in S100B(Ϫ/Ϫ) animals in vivo (Sakatani et al, 2007). In the current study, we explored factors that contribute to the reduced gamma oscillations.…”

“…Behavioral assessments using such animals show that hippocampusdependent memory is affected (Gerlai et al, 1995;Nishiyama et al, 2002). At the neural dynamics level, kainate (KA)-induced hippocampal CA1 gamma oscillations are attenuated in S100B(Ϫ/Ϫ) mice in vivo (Sakatani et al, 2007); however, the underling mechanism has been unclear. Here, we demonstrate that S100B is released to the extracellular space in a neural and synaptic-activity-dependent manner.…”

In VivoIntracellular Recording Suggests That Gray Matter Astrocytes in Mature Cerebral Cortex and Hippocampus Are Electrophysiologically Homogeneous

“…Astrocytic membrane potential traces were averaged based on LFP event triggers, which were detected as described by Sakatani et al (2007). Briefly, the raw wide-band extracellular recording data were first downsampled to 1.25 kHz.…”