Shinichi Kogure

Ih blockers have a potential of antiepileptic effects.

Summary:  Purpose: The h current (Ih) is an inwardly mixed cationic conductance activated by membrane hyperpolarization and distributed predominantly in the apical dendrites of hippocampal pyramidal neurons. To verify a hypothesis that an anomalous hyperpolarization generates an abnormal excitation by way of Ih channels, we examined the effects of Ih blockers (CsCl and ZD7288) on electrically induced paroxysmal discharges (PADs).

Fast Fourier transformation analysis of kindling-induced afterdischarge in the rabbit hippocampus

Kindling is a widely used animal model of intractable temporal lobe epilepsy. In the present study, we performed fast Fourier transformation (FFT) analysis of kindling-induced afterdischarge (AD) in the rabbit hippocampus. Ten adult rabbits were used. Kindling stimulation to the right hippocampus was delivered as a train of biphasic pulses (1 ms duration each) of 50 Hz for 1s, with suprathreshold intensity for AD. Motor responses were classified into five stages according to the conventional criteria. Of 10 animals, five developed stage 5 convulsions with a mean of 21 stimulations (kindled (K) group), while the remaining five animals did not (incomplete kindling (IK) group). We standardized each ratio of power spectral density of lower frequency band component (LFB: 0-9 Hz) and the higher frequency band (HFB: 12-30 Hz) in the initial stage as 1.0. The IK group exhibited small decrements (0.99 and 0.94 times) in LFB and HFB components at the final stage. In contrast, the K group exhibited a significantly (p<0.05) large decrement (0.49 times) in the LFB component and a very large increment (4.45 times) of HFB component at the final stage. Correlation analyses were performed between alteration of power spectral density ratio of the HFB component and AD duration, interictal discharge frequency, and behavioral stage during kindling progression. Fairly strong positive correlations were found in all cases in the K group. FFT analysis of kindling-induced AD demonstrated an important role of the HFB component: enhancement of the HFB component is associated with kindled stage, while decrement of it is associated with incomplete kindling stage. These findings suggest that FFT analysis of stimulus-induced and spontaneous seizure discharges is useful for examination of the progression of epileptic disorders.

532 nm low-power laser irradiation recovers γ-secretase inhibitor-mediated cell growth suppression and promotes cell proliferation via Akt signaling.

Background and Objective The γ-secretase inhibitor (GSI) has been shown to inhibit expression of amyloid beta (Aβ), but GSI also has a side effect of reducing cell survival. Since low-power laser irradiation (LLI) has been known to promote cell survival, we examined whether 532 nm LLI can rescue the GSI side effect or not. Study Design/Materials and Methods The human-derived glioblastoma cells (A-172) were cultured in 35 mm culture dishes or 96-well plate. The center of dish or selected wells was irradiated with 532 nm laser (Nd:YVO4, CW, 60 mW) for 20, 40 and 60 min, respectively. The irradiated cells were photographed at immediately after, 24 and 48 h later and counted. GSI was supplemented in medium 3 h before LLI. The MTT assay was also used to estimate viable cells at 48 h after irradiation. The expression of phosphorylated Akt (p-Akt) or phosphorylated PTEN (p-PTEN) was examined by immunofluorescent staining and measured by fluorescence intensity using the software (BZ-9000, KEYENCE, Japan). Results GSI application depressed cell proliferation as well as cell survival compared to control. GSI down-regulated Aβ but up-regulated p-PTEN and suppressed p-Akt. Application of 532 nm LLI in the presence of GSI significantly recovered the GSI-mediated effects, i.e., LLI could decrease elevated p-PTEN, while increased p-Akt expression with keeping Aβ suppression. The LLI effects had a dose-dependency. Conclusion We confirmed that GSI potently suppressed intracellular Aβ and decreased cell survival. We conclude that a combination of GSI application and 532 nm LLI can increase cell proliferation via Akt activation while keeping PTEN and Aβ suppressed.

Properties of interictal discharges induced by hippocampal kindling.

The present experiment was designed to reveal the characteristics of interictal discharges (IIDs) induced by kindling of the rabbit hippocampus. Out of 21 animals, 13 developed stage 5 convulsions with a mean of 18 stimulations (Kindled (K) group), whereas the remaining eight animals did not (incomplete kindling (IK) group). A correlation between the duration of the afterdischarge and the behavioral stages was found in the K group. However, changes in frequency of total IIDs during kindling did not differ between the two groups. In the acute experiments performed after kindling, IIDs were classified into two types: simple and complex IIDs. The former was further classified into two subtypes (A and B) according to the laminar profile in the CA1 region. The A type of simple IIDs showed a negative polarity in the apical dendritic layer, while the B type showed a negative polarity in the basal dendritic layer. Complex IIDs basically consisted of two to three simple IIDs and were often followed by large irregular activity. Retrospective analysis was done, based on the classification of IIDs in the acute experiments (n = 12). Consequently, in the K group (n = 7), the frequency of complex IIDs rather than that of simple ones was closely related to the enhancement of behavioral responses during kindling. On the other hand, in the IK group (n = 5), simple IIDs occurred at a higher frequency, and did not parallel the changes in seizure behavior. It is concluded that complex IIDs play an important role in the propagation as well as the evolution of kindling effects.

Simultaneous Kindling of the Bilateral Hippocampi: An Advanced Model for Epilepsy Research

Summary: Purpose: To examine whether simultaneous kindling of bilateral hippocampi [bilateral kindling (BK)] could accelerate the achievement of seizures by the breakdown of kindling antagonism or decelerate the achievement of seizures by its enhancement.

Simultaneous recordings from two types of hippocampal nonpyramidal cells during electrically induced paroxysmal discharges

To reveal the relationship between hippocampal nonpyramidal cells and seizure activity, single-unit activities of nonpyramidal cells were studied during electrically induced paroxysmal discharges in the hippocampal CA1 region of lightly anesthetized rabbits. Type I nonpyramidal cells (N = 21) that were located in or near the pyramidal cell layer tended to cease firing during the early part of paroxysmal discharges, but refired during the late part. In contrast, type II nonpyramidal cells (N = 14) which were found in the inferior subzone of the stratum oriens continued to fire during the entire course of the paroxysmal discharge.

Epileptogenesis Induced by Alternate-site Kindling in Bilateral Hippocampi

Summary:  Purpose: Alternate‐site kindling (AK), which has been known to induce so‐called kindling antagonism, was performed in the bilateral hippocampi to reveal neural mechanisms underlying hippocampal kindling.

The extracellular current blocking effect of cesium chloride on the theta wave in the rabbit hippocampal CA1 region

We studied the extracellular effects of cesium chloride (CsCl), a blocker of the hyperpolarization-activated cationic current (I(h)), on the hippocampal theta wave in pentobarbital-anesthetized rabbits. We recorded spontaneous field potentials at the hippocampal CA1 region before and at three time periods after CsCl or saline injections. We found that CsCl injected into the apical dendritic layer attenuated the theta wave amplitude. CsCl affected neither the frequency nor the phase reversal of the theta wave between the apical and basal dendritic layers. Our findings indicate that I(h) in pyramidal neurons contributes to current generation of the limbic theta wave in vivo.

Spectral analysis of bilateral or alternate-site kindling-induced afterdischarges in the rabbit hippocampi

Kindling is one of the popular animal models of temporal lobe epilepsy. In the present study following the previous results obtained using unilateral hippocampal kindling (UK), we performed spectral analysis of bilateral or alternate-site kindling-induced afterdischarges (ADs) in the rabbit hippocampi. Eight and ten adult rabbits were used for bilateral kindling (BK) and alternate-site kindling (AK), respectively. Kindling stimuli consisted of a train of biphasic pulses (1ms duration each) of 50Hz for 1s, with suprathreshold intensity for AD. The stimulations were applied simultaneously to the bilateral hippocampi in the BK and were delivered to the right and left hippocampus once every 24h in the AK. Motor responses were classified into five stages according to the conventional criteria. All animals in BK as well as AK developed stage 5 convulsions. This contrasts to the result of UK (kindled: 50%; incomplete: 50%). We normalized power spectral density (PSD) and monitored the changes in the proportion of lower frequency band component (LFB: 0-9Hz) and the higher frequency band (HFB: 12-30Hz). BK animals showed a significantly large decrement (0.5 times, p<0.01) in LFB component at the final stage compared to the initial stage, but a very large increment (4.7 times) in HFB component. Likewise, AK animals exhibited a significantly large decrement (0.6 times, p<0.01) in LFB component at the final stage, but a very large increment (3.6 times) in HFB component. Correlation analyses were performed between the HFB component and AD duration, interictal discharge frequency, and behavioral stages during kindling progression. Very strong positive correlations were found in both kindling animals. Chronological spectral analysis of seizure discharges, resulting in a pattern of LFB decrement accompanied by HFB increment, is a convenient tool to investigate epileptic disorders and diagnose epileptic states.

Effects of 808 nm low-power laser irradiation on the muscle contraction of frog gastrocnemius

The efficacy of low‐power laser irradiation (LLI) on muscle fibers remains unclear; therefore, we examined the effect of LLI (808 nm: 60 or 100 mW) on muscle contraction and conducted waveform analyses of the twitch curve, including alterations in the peak amplitudes of tension (AMP), latency (LAT), contraction period (CP), and relaxation period (RP).