Atipamezole, a specific alpha(2A) antagonist, suppresses spike-and-wave discharges and alters Ca2+/calmodulin-dependent protein kinase II in the thalamus of genetic absence epilepsy rats

Objective The role of alpha(2A) adrenergic receptors (alpha(2A)ARs) in absence epilepsy is not well characterized. Therefore, we investigated the outcomes of the specific antagonism of alpha(2A)ARs on the spike-and-wave discharges (SWDs) in genetic absence epilepsy rats from Strasbourg (GAERSs), together with its influence on the behavior and second messenger systems, which may point to the mechanisms to which a possible SWD modulation can be related. Methods Atipamezole, an alpha(2A)AR antagonist, was administered intracerebroventricularly to the adult GAERSs, and electroencephalography (EEG) was conducted. The cumulative duration and number of SWDs, and the mean duration of each SWD complex were counted. The relative power of the EEG frequency bands and behavioral activity after the acute application of two doses (12 and 31 mu g/5 mu L) of atipamezole were evaluated. The levels of cyclic adenosine monophosphate and calcium/calmodulin-dependent kinase II (CaMKII) were measured in the cortex, thalamus, and hippocampus of naive Wistar rats and GAERSs, administered with artificial cerebrospinal fluid (aCSF) as a vehicle, or either acute or chronic atipamezole (12 mu g), the latter being administered for 5 consecutive days. Results Atipamezole significantly suppressed SWDs dose-dependently, without affecting the relative power values of EEG frequency spectrum. The stereotypic activity was significantly lower in both naive Wistar rats and GAERSs receiving the highest dose (31 mu g) of atipamezole compared to GAERSs receiving aCSF. In GAERSs, CaMKII levels were found to be higher in the thalamus after the acute and chronic application of SWD-suppressing doses of atipamezole (12 and 31 mu g) compared to aCSF. Significance This study emphasizes the alpha(2)AR-related modulation of absence epilepsy and particularly the significance of alpha(2)AR antagonism in suppressing SWDs. Atipamezole's SWD-suppressive actions may be through CaMKII-mediated second messenger systems in the thalamus

Experimental modal analysis of graphene nanoparticle-reinforced adhesively bonded double strap joints

ACAR, VOLKAN/0000-0001-7412-301X; Akbulut, Hamit/0000-0003-0061-5067; UNAL, HASAN YAVUZ/0000-0003-1934-7445; Aydin, Onur Ahmet/0000-0001-6403-7951; AYDIN, Muhammet Raci/0000-0002-4120-1816; Hulagu, Burak/0000-0001-8381-578XWOS: 000518272600001This study performed an experimental modal analysis and investigated the mechanical properties of graphene nanoparticle (GNP)-reinforced, adhesively bonded double strap joints (DSJs). the DP270 structural adhesive was reinforced with graphene nanoparticles by using five different manufacturing methods and bulk specimens were prepared with 1%, 2% and 3% reinforcement by weight. the dispersion of graphene was observed by using scanning electron microscopy (SEM) because its efficient distribution in the adhesive is directly affected by the mechanical and modal properties of the modified polymer. Furthermore, the damping ratios and natural frequencies of the bulk specimens were also determined. Based on the dynamic characteristics and SEM observations, the most appropriate method to manufacture the joints was selected, and DSJs were prepared by using AA 2024-T3 aluminum alloy as the adherend. After that, the modal and tensile properties of the graphene-reinforced DSJs were determined. Consequently, it was observed that a graphene reinforcement ratio of 2% by weight showed a 36% increase in the damping ratio of the adhesive and a 23% increase in the damping ratio of the joint. in addition, it was observed that graphene reinforcement resulted in up to an 81% increase in the failure strength of the modified DSJs.Ataturk University Scientific Research Projects FundAtaturk University [FBA-2017-6243]This work was supported by Ataturk University Scientific Research Projects Fund [FBA-2017-6243

Low-velocity impact and bending response of graphene nanoparticle-reinforced adhesively bonded double strap joints

AYDIN, Muhammet Raci/0000-0002-4120-1816; Akbulut, Hamit/0000-0003-0061-5067; UNAL, HASAN YAVUZ/0000-0003-1934-7445WOS:000620526200001The low-velocity impact and bending performance of adhesive joints are critically important for their reliable use in multiple industrial applications. Enhancements of adhesive joints' mechanical properties are significantly valuable for the long-term safe use and overall life of structural components. This study investigated the low-velocity impact and bending properties of double strap joints (DSJs) reinforced with graphene nanoplatelets (GNPs). in this context, GNP-reinforced adhesives with 1%, 2%, and 3% reinforcement by weight were prepared, and the dispersion quality of graphene was examined using scanning electron microscopy. Subsequently, graphene-modified DSJs were manufactured and mechanical tests were carried out. Low-velocity impact tests were performed at 5 J and 10 J energies in a single impact configuration. Tests of the nonperforated specimens showed that the contact force increased with graphene reinforcement. The absorbed energy and the contact time of the specimens with the impactor tip decreased with nano reinforcement by 5% and 4%, respectively. Additionally, a significant decrease in the displacement was observed with 2% and 3% graphene reinforcements. Significant improvements of up to 58% were observed in the flexural strength of the joints with graphene reinforcement.Ataturk University Research GrantAtaturk University [FBA-2017-6243]This research was supported by Ataturk University Research Grant (Grant Number: FBA-2017-6243). The authors would like to thank Mr. Murat Top and Mr. Fatih Tutar for their technical assistance

Atipamezole, a specific alpha(2A) antagonist, suppresses spike-and-wave discharges and alters Ca2+/calmodulin-dependent protein kinase II in the thalamus of genetic absence epilepsy rats

AYDIN, BANU/0000-0002-3267-8620WOS: 000583280100001PubMed: 33098125Objective the role of alpha(2A) adrenergic receptors (alpha(2A)ARs) in absence epilepsy is not well characterized. Therefore, we investigated the outcomes of the specific antagonism of alpha(2A)ARs on the spike-and-wave discharges (SWDs) in genetic absence epilepsy rats from Strasbourg (GAERSs), together with its influence on the behavior and second messenger systems, which may point to the mechanisms to which a possible SWD modulation can be related. Methods Atipamezole, an alpha(2A)AR antagonist, was administered intracerebroventricularly to the adult GAERSs, and electroencephalography (EEG) was conducted. the cumulative duration and number of SWDs, and the mean duration of each SWD complex were counted. the relative power of the EEG frequency bands and behavioral activity after the acute application of two doses (12 and 31 mu g/5 mu L) of atipamezole were evaluated. the levels of cyclic adenosine monophosphate and calcium/calmodulin-dependent kinase II (CaMKII) were measured in the cortex, thalamus, and hippocampus of naive Wistar rats and GAERSs, administered with artificial cerebrospinal fluid (aCSF) as a vehicle, or either acute or chronic atipamezole (12 mu g), the latter being administered for 5 consecutive days. Results Atipamezole significantly suppressed SWDs dose-dependently, without affecting the relative power values of EEG frequency spectrum. the stereotypic activity was significantly lower in both naive Wistar rats and GAERSs receiving the highest dose (31 mu g) of atipamezole compared to GAERSs receiving aCSF. in GAERSs, CaMKII levels were found to be higher in the thalamus after the acute and chronic application of SWD-suppressing doses of atipamezole (12 and 31 mu g) compared to aCSF. Significance This study emphasizes the alpha(2)AR-related modulation of absence epilepsy and particularly the significance of alpha(2)AR antagonism in suppressing SWDs. Atipamezole's SWD-suppressive actions may be through CaMKII-mediated second messenger systems in the thalamus.Marmara UniversitesiMarmara University [BAPKO-SAG-C-BRP-131016-0435, SAG-P-150218-0047]; Marmara UniversityMarmara University [2018]Marmara Universitesi, Grant/Award Number: BAPKO-SAG-C-BRP-131016-0435 and SAG-P-150218-0047; Marmara University, Grant/Award Number: 201