Genetic inactivation of the sigma-1 chaperone protein results in decreased expression of the R2 subunit of the GABA-B receptor and increased susceptibility to seizures.

There is a growing body of evidence demonstrating the significant involvement of the sigma-1 chaperone protein in the modulation of seizures. Several sigma-1 receptor (Sig1R) ligands have been demonstrated to regulate the seizure threshold in acute and chronic seizure models. However, the mechanism by which Sig1R modulates the excitatory and inhibitory pathways in the brain has not been elucidated. The aim of this study was to compare the susceptibility to seizures of wild type (WT) and Sig1R knockout (Sig1R-/-) mice in intravenous pentylenetetrazol (PTZ) and (+)-bicuculline (BIC) infusion-induced acute seizure and Sig1R antagonist NE-100-induced seizure models. To determine possible molecular mechanisms, we used quantitative PCR, Western blotting and immunohistochemistry to assess the possible involvement of several seizure-related genes and proteins. Peripheral tissue contractile response of WT and Sig1R-/- mice was studied in an isolated vasa deferentia model. The most important finding was the significantly decreased expression of the R2 subunit of the GABA-B receptor in the hippocampus and habenula of Sig1R-/- mice. Our results demonstrated that Sig1R-/- mice have decreased thresholds for PTZ- and BIC-induced tonic seizures. In the NE-100-induced seizure model, Sig1R-/- animals demonstrated lower seizure scores, shorter durations and increased latency times of seizures compared to WT mice. Sig1R-independent activities of NE-100 included downregulation of the gene expression of iNOS and GABA-A γ2 and inhibition of KCl-induced depolarization in both WT and Sig1R-/- animals. In conclusion, the results of this study indicate that the lack of Sig1R resulted in decreased expression of the R2 subunit of the GABA-B receptor and increased susceptibility to seizures. Our results confirm that Sig1R is a significant molecular target for seizure modulation and warrants further investigation for the development of novel anti-seizure drugs.

Reduced GFAP Expression in Bergmann Glial Cells in the Cerebellum of Sigma-1 Receptor Knockout Mice Determines the Neurobehavioral Outcomes after Traumatic Brain Injury.

Neuroprotective effects of Sigma-1 receptor (S1R) ligands have been observed in multiple animal models of neurodegenerative diseases. Traumatic brain injury (TBI)-related neurodegeneration can induce long-lasting physical, cognitive, and behavioral disabilities. The aim of our study was to evaluate the role of S1R in the development of neurological deficits after TBI. Adult male wild-type CD-1 (WT) and S1R knockout (S1R-/-) mice were subjected to lateral fluid percussion injury, and behavioral and histological outcomes were assessed for up to 12 months postinjury. Neurological deficits and motor coordination impairment were less pronounced in S1R-/- mice with TBI than in WT mice with TBI 24 h after injury. TBI-induced short-term memory impairments were present in WT but not S1R-/- mice 7 months after injury. Compared to WT animals, S1R-/- mice exhibited better motor coordination and less pronounced despair behavior for up to 12 months postinjury. TBI induced astrocyte activation in the cortex of WT but not S1R-/- mice. S1R-/- mice presented a significantly reduced GFAP expression in Bergmann glial cells in the molecular layer of the cerebellum compared to WT mice. Our findings suggest that S1R deficiency reduces TBI-induced motor coordination impairments by reducing GFAP expression in Bergmann glial cells in the cerebellum.

Safety and Tolerability of the Anxiolytic and Nootropic Drug Phenibut: A Systematic Review of Clinical Trials and Case Reports.

Phenibut is a nootropic drug that exerts anxiolytic and antinociceptive effects by acting on the GABAB receptor and the α2-δ subunit of voltage-dependent calcium channels. An increased number of reports of dependence to and intoxication by phenibut purchased online on the one hand and the wide prescription of phenibut in Eastern Europe for more than half a century on the other hand have resulted in a number of controversies regarding its use. In this review, we have summarized currently available information from case reports of phenibut dependence and intoxication and safety data from clinical trials. We included 14 dependence and intoxication case reports (16 patients) and reviewed 11 phenibut clinical trials (583 patients). The clinical symptoms in the case reports included cardiovascular effects, insomnia, anxiety and agitation, hallucinations, and depressed level of consciousness. In addition, the doses used (0.5-100 g/day) were much higher than the recommended daily dose (0.25-2 g/day). An analysis of phenibut side effects described in the clinical trials showed adverse events in only 5.66% of patients, and the most reported side effect was somnolence (1.89%). There are discrepancies in the reported side effects of phenibut in clinical trials compared to those reported in cases of online-purchased phenibut dependence and intoxication. The current systematic review provides evidence that, at therapeutic doses, phenibut is safe and well tolerated with minor adverse effects, but questions regarding the quality of phenibut obtained online and the contribution of alcohol and other drug abuse to phenibut dependence and intoxication remain open.

Neuroprotective and anti-inflammatory activity of DAT inhibitor R-phenylpiracetam in experimental models of inflammation in male mice.

R-phenylpiracetam (R-PhP, (4R)-2-(4-phenyl-2-oxopyrrolidin-1-yl)acetamide) is an optical isomer of phenotropil, a clinically-used nootropic drug that improves physical condition and cognition. Recently, R-PhP was shown to bind to the dopamine transporter (DAT). Since growing evidence suggests that dysfunction of the dopaminergic system is associated with persistent neuroinflammation, the aim of this study was to determine whether R-PhP, an inhibitor of DAT, has neuroprotective and anti-inflammatory effects in male mice. The pharmacokinetic profiles of R-PhP in mouse plasma and its bioavailability in brain tissue were assessed. To study possible molecular mechanisms involved in the anti-inflammatory activity of R-PhP, target profiling was performed using radioligand binding and enzymatic activity assays. To clarify the neuroprotective and anti-inflammatory effects of R-PhP, we used a lipopolysaccharide (LPS)-induced endotoxaemia model characterized by reduced body temperature and overexpression of inflammatory genes in the brain. In addition, the antinociceptive and anti-inflammatory effects of R-PhP were tested using carrageenan-induced paw oedema and formalin-induced paw-licking tests. R-PhP (50 mg/kg) reached the brain tissue 15 min after intraperitoneal (ip) and peroral (po) injections. The maximal concentration of R-PhP in the brain tissues was 28 µg/g and 18 µg/g tissue after ip and po administration, respectively. In radioligand binding assays, DAT was the only significant molecular target found for R-PhP. A single ip injection of R-PhP significantly attenuated the LPS-induced body temperature reduction and the overexpression of inflammatory genes, such as tumour necrosis factor-α (TNF-α), interleukin 1 beta (IL-1ß) and inducible nitric oxide synthase (iNOS). Seven-day po pretreatment with R-PhP dose-dependently reduced paw oedema and the antinociceptive response, as shown by the carrageenan-induced paw oedema test. In addition, R-PhP decreased the nociceptive response during the inflammatory phase in the formalin-induced paw-licking test. Our study showed that R-PhP possesses neuroprotective and anti-inflammatory effects, demonstrating the potential of DAT inhibitors as effective therapeutics.

Knockout of Tmlhe in mice is not associated with autism spectrum disorder phenotypes or motor dysfunction despite low carnitine levels.

Deletion of exon 2 of the trimethyllysine hydroxylase epsilon (TMLHE) gene was identified in probands with autism spectrum disorder (ASD). TMLHE encodes the first enzyme in carnitine biosynthesis, N6-trimethyllysine dioxygenase (TMLD). Researchers have suggested that carnitine depletion could be important for the development of ASD and cognitive, locomotor and social dysfunctions, but previous findings have been inconclusive regarding the specific role of endogenous carnitine. We developed a mouse knockout model with constitutive TMLD enzyme inactivation that exhibited a significant decrease in the carnitine by more than 90% compared to wild-type (WT) mice. However, we did not observe any significant social, cognitive, or repetitive-behavior changes associated with ASD in the knockout mice; muscle strength and coordination were also not affected. In addition, the life expectancy of knockout mice was similar to that of WT mice. In conclusion, knockout of Tmlh in mice does not induce an ASD phenotype or motor dysfunction despite extremely low carnitine and gamma-butyrobetaine concentrations. Moreover, inactivation of TMLD does not induce a phenotype similar to previously described primary carnitine deficiency; indeed, our results showed that low levels of carnitine sustained adequate energy production, muscle function and social behavior in mice.

Moderate traumatic brain injury triggers long-term risks for the development of peripheral pain sensitivity and depressive-like behavior in mice.

As traumatic brain injury (TBI) is one of the major causes of permanent disability, there is increasing interest in the long-term outcome of TBI. While motor deficits, cognitive impairment and longer-term risks of neurodegenerative disease are well-established consequences in animal models of TBI, pain is discussed less often despite its high prevalence. The current study addresses the need to characterize the extent of chronic pain and long-term behavioral impairments induced by moderate lateral fluid percussion injury (latFPI) in mice up to 12 months post-TBI and evaluates the validity of the model. Adult male BALB/c mice were subjected to latFPI, and the results were compared with outcomes in sham-operated mice. Mouse behavior was assessed at 1 and 7 days and 1, 3, 6, 9, and 12 months post-injury using sensory-motor (neurological severity score, NSS), cold (acetone) and mechanical sensitivity (von Frey), depressive-like behavior (tail suspension), locomotor (open field), motor coordination (rotarod) and cognitive (Morris water maze, y-maze, passive avoidance) tests. Animals with TBI demonstrated significantly higher NSS than the sham-operated group for up to 9 months after the injury. Cold sensitization was significantly increased in the contralateral hind paw in the TBI group compared to that of the sham group at 3, 6, and 9 months after TBI. In the von Frey test, the withdrawal threshold of the contralateral and ipsilateral hind paws was reduced at 6 months after TBI and lasted for up to 12 months post-injury. latFPI induced progressive depressive-like behavior starting at 6 months post-injury. No significant deficits were observed in memory, motor coordination or locomotion over the 12-month assessment period. The present study demonstrates that moderate TBI in mice elicits long-lasting impairment of sensory-motor function, results in progressive depression and potentiates peripheral pain. Hence, the latFPI model provides a relevant preclinical setting for the study of the link between brain injury and chronic sequelae such as depression and peripheral pain.

Antidepressive-like Behavior-Related Metabolomic Signatures of Sigma-1 Receptor Knockout Mice.

Sigma-1 receptor (Sig1R) has been proposed as a therapeutic target for neurological, neurodegenerative, and psychiatric disorders, including depression and anxiety. Identifying metabolites that are affected by Sig1R absence and cross-referencing them with specific mood-related behaviors would be helpful for the development of new therapies for Sig1R-associated disorders. Here, we examined metabolic profiles in the blood and brains of male CD-1 background Sig1R knockout (KO) mice in adulthood and old age and correlated them with the assessment of depression- and anxiety-related behaviors. The most pronounced changes in the metabolic profile were observed in the plasma of adult Sig1R KO mice. In adult mice, the absence of Sig1R significantly influenced the amino acid, sphingolipid (sphingomyelin and ceramide (18:1)), and serotonin metabolic pathways. There were higher serotonin levels in plasma and brain tissue and higher histamine levels in the plasma of Sig1R KO mice than in their age-matched wild-type counterparts. This increase correlated with the reduced behavioral despair in the tail suspension test and lack of anhedonia in the sucrose preference test. Overall, these results suggest that Sig1R regulates behavior by altering serotonergic and histaminergic systems and the sphingolipid metabolic pathway.

Low cardiac content of long-chain acylcarnitines in TMLHE knockout mice prevents ischaemia-reperfusion-induced mitochondrial and cardiac damage.

Increased tissue content of long-chain acylcarnitines may induce mitochondrial and cardiac damage by stimulating ROS production. N6-trimethyllysine dioxygenase (TMLD) is the first enzyme in the carnitine/acylcarnitine biosynthesis pathway. Inactivation of the TMLHE gene (TMLHE KO) in mice is expected to limit long-chain acylcarnitine synthesis and thus induce a cardio- and mitochondria-protective phenotype. TMLHE gene deletion in male mice lowered acylcarnitine concentrations in blood and cardiac tissues by up to 85% and decreased fatty acid oxidation by 30% but did not affect muscle and heart function in mice. Metabolome profile analysis revealed increased levels of polyunsaturated fatty acids (PUFAs) and a global shift in fatty acid content from saturated to unsaturated lipids. In the risk area of ischemic hearts in TMLHE KO mouse, the OXPHOS-dependent respiration rate and OXPHOS coupling efficiency were fully preserved. Additionally, the decreased long-chain acylcarnitine synthesis rate in TMLHE KO mice prevented ischaemia-reperfusion-induced ROS production in cardiac mitochondria. This was associated with a 39% smaller infarct size in the TMLHE KO mice. The arrest of the acylcarnitine biosynthesis pathway in TMLHE KO mice prevents ischaemia-reperfusion-induced damage in cardiac mitochondria and decreases infarct size. These results confirm that the decreased accumulation of ROS-increasing fatty acid metabolism intermediates prevents mitochondrial and cardiac damage during ischaemia-reperfusion.

Mitochondrial-Protective Effects of R-Phenibut after Experimental Traumatic Brain Injury.

Altered neuronal Ca2+ homeostasis and mitochondrial dysfunction play a central role in the pathogenesis of traumatic brain injury (TBI). R-Phenibut ((3R)-phenyl-4-aminobutyric acid) is an antagonist of the α 2 δ subunit of voltage-dependent calcium channels (VDCC) and an agonist of gamma-aminobutyric acid B (GABA-B) receptors. The aim of this study was to evaluate the potential therapeutic effects of R-phenibut following the lateral fluid percussion injury (latFPI) model of TBI in mice and the impact of R- and S-phenibut on mitochondrial functionality in vitro. By determining the bioavailability of R-phenibut in the mouse brain tissue and plasma, we found that R-phenibut (50 mg/kg) reached the brain tissue 15 min after intraperitoneal (i.p.) and peroral (p.o.) injections. The maximal concentration of R-phenibut in the brain tissues was 0.6 µg/g and 0.2 µg/g tissue after i.p. and p.o. administration, respectively. Male Swiss-Webster mice received i.p. injections of R-phenibut at doses of 10 or 50 mg/kg 2 h after TBI and then once daily for 7 days. R-Phenibut treatment at the dose of 50 mg/kg significantly ameliorated functional deficits after TBI on postinjury days 1, 4, and 7. Seven days after TBI, the number of Nissl-stained dark neurons (N-DNs) and interleukin-1beta (IL-1ß) expression in the cerebral neocortex in the area of cortical impact were reduced. Moreover, the addition of R- and S-phenibut at a concentration of 0.5 µg/ml inhibited calcium-induced mitochondrial swelling in the brain homogenate and prevented anoxia-reoxygenation-induced increases in mitochondrial H2O2 production and the H2O2/O ratio. Taken together, these results suggest that R-phenibut could serve as a neuroprotective agent and promising drug candidate for treating TBI.

Skull Fractures Induce Neuroinflammation and Worsen Outcomes after Closed Head Injury in Mice.

The weight-drop model is used widely to replicate closed-head injuries in mice; however, the histopathological and functional outcomes may vary significantly between laboratories. Because skull fractures are reported to occur in this model, we aimed to evaluate whether these breaks may influence the variability of the weight-drop (WD) model. Male Swiss Webster mice underwent WD injury with either a 2 or 5 mm cone tip, and behavior was assessed at 2 h and 24 h thereafter using the neurological severity score. The expression of interleukin (IL)-6, IL-1ß, tumor necrosis factor-α, matrix metalloproteinase-9, and tissue inhibitor of metalloproteinase-1 genes was measured at 12 h and 1, 3, and 14 days after injury. Before the injury, micro-computed tomography (micro-CT) was performed to quantify skull thickness at the impact site. With a conventional tip diameter of 2 mm, 33% of mice showed fractures of the parietal bone; the 5 mm tip produced only 10% fractures. Compared with mice without fractures, mice with fractures had a severity-dependent worse functional outcome and a more pronounced upregulation of inflammatory genes in the brain. Older mice were associated with thicker parietal bones and were less prone to skull fractures. In addition, mice that underwent traumatic brain injury (TBI) with skull fracture had macroscopic brain damage because of skull depression. Skull fractures explain a considerable proportion of the variability observed in the WD model in mice-i.e., mice with skull fractures have a much stronger inflammatory response than do mice without fractures. Using older mice with thicker skull bones and an impact cone with a larger diameter reduces the rate of skull fractures and the variability in this very useful closed-head TBI model.

Data on analysis of MK-801 bioavailability in mouse plasma and brain tissue by ultra-performance liquid chromatography-tandem mass spectrometry.

MK-801, a N-methyl-d-aspartate receptor antagonist, is widely used in animal preclinical experiments to induce memory and learning impairments and schizophrenia-like behavior. In the present study, we compared the plasma and brain tissue concentrations of MK-801 after intraperitoneal (i.p.) or subcutaneous (s.c.) administration at a dose of 0.1 mg/kg in male ICR mice. Moreover, these data present the optimization of ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) for the analysis of MK-801 in biological samples. Procedures for the preparation of brain tissue and plasma samples and instrumental analysis are described. This article is related to a research article entitled "Effects of the N-methyl-d-aspartate receptor antagonist, MK-801, on spatial memory and influence of the route of administration" [1].

Effects of the N-methyl-d-aspartate receptor antagonist, MK-801, on spatial memory and influence of the route of administration.

The N-methyl-d-aspartate receptor antagonist, MK-801, is widely used to induce memory and learning impairments in preclinical studies. MK-801 is mainly injected intraperitoneally (i.p.) at doses that result in cognitive impairment and induction of motor or sensory disturbances. The aim of this study was to compare the behavioral outcomes when different administration routes (subcutaneous (s.c.) and i.p.) and MK-801 doses (0.01, 0.05, and 0.1 mg/kg) are employed in the Morris water maze (MWM) task. We also assessed the pharmacokinetics of MK-801 in rat blood plasma and its bioavailability in brain tissue. The concentrations of MK-801 in brain tissue and blood plasma were significantly higher after s.c. than i.p. administration. MK-801 administered via the s.c. route at doses of 0.1 and 0.05 mg/kg significantly impaired learning on all training days in the MWM task compared to i.p. administration at the same doses. Memory in the probe trial was significantly impaired after MK-801 administration via both routes at all doses. MK-801 also induced locomotor disturbances after i.p. and s.c. administration at the highest dose (0.1 mg/kg). Our data suggest that s.c. administration leads to higher MK-801 concentrations in brain tissue and blood plasma and evidently impairs spatial learning and memory compared to i.p. administration at the same dose. Knowledge of MK-801 concentrations in the brain and blood and the effects of the compound on memory processes and locomotor activity enable the choice of more targeted routes and doses of administration in preclinical studies.