Electroacupuncture attenuates ketamine-induced neuronal injury in the locus coeruleus of rats through modulation of the CAMK II/CREB pathway.

BACKGROUND: Ketamine, despite its efficacy in treating depression, raises concerns regarding safety due to potential abuse, cognitive impairment, and bladder toxicity. Ketamine can affect the locus coeruleus (LC) norepinephrine and attention networks. This study explored the protective effects of electroacupuncture (EA) on the LC of rats exposed to repeated administration of ketamine while investigating the potential role of the Calcium CaM-dependent protein kinase II (CAMK II)/ cAMP response element binding protein (CREB) pathway in mediating EA's impact on ketamine-induced neuronal injury in LC. METHODS: Rats were repeatedly injected intraperitoneally with ketamine hydrochloride (50 mg/kg) once daily for seven days. Subsequently, EA was performed at the acupoints "Zusanli" (ST36) and "Sanyinjiao" (SP-6) once daily following ketamine administration. The Morris water maze test was employed to assess behavioral changes in the rats. Neuronal injury was examined using Nissl staining, and the expression of CAMK II, CREB, and phospho-CREB (p-CREB) was evaluated through immunohistochemistry and western blotting. RESULTS: EA mitigated the cognitive and exploratory impairments and attenuated neuronal injury in the LC induced by repeated administration of ketamine. The expression of CAMK II and p-CREB proteins in the LC increased following 7 days of ketamine administration. However, EA treatment led to a downregulation of CAMK II and p-CREB expression. CONCLUSION: Repeated administration of ketamine in male rats can lead to neuronal injury and neurobehavioral dysfunction. However, EA was found to ameliorate neurodegeneration in the LC and enhance neurobehavioral symptoms. This therapeutic effect of EA may be attributed to its modulation of the CAMKII/CREB pathway, thereby mitigating the aforementioned adverse effects.

Prevention and reversal of ketamine-induced experimental psychosis in mice by the neuroactive flavonoid, hesperidin: The role of oxidative and cholinergic mechanisms.

Currently, prevailing evidence have identified cholinergic and oxidative pathways as important therapeutic targets for abating ketamine-induced schizophrenia-like behavior. Thus, this study evaluated the ability of hesperidin, a naturally occurring antioxidant and neuroprotective flavonoid, to prevent and reverse ketamine-induced schizophrenia-like behaviors and changes in cholinergic, oxidative and nitrergic status in mice. Forty-eight male Swiss mice were allotted into the preventive and reversal studies with 4 groups (n = 6) each. In the preventive study, groups 1 and 2 received vehicle (10 mL/kg/p.o./day), while groups 3 and 4 had hesperidin (100 mg/kg/p.o./day) for 14 days, but ketamine (20 mg/kg/i.p./day) was concurrently given to groups 2 and 4 from days 8-14. In the reversal study, groups 1 and 3 received vehicle, groups 2 and 4 were pretreated with ketamine for 14 days. Nevertheless, groups 3 and 4 additionally received hesperidin from days 8-14. Thereafter, schizophrenia-like behavior from exploratory activity, open-field (positive symptoms), Y-maze (cognitive symptoms) and social interaction (negative symptoms) tests were evaluated. Brain levels of oxidative/nitrergic (glutathione, superoxide-dismutase, malondialdehyde and nitrite levels) and cholinergic (acetylcholinesterase activity) markers were measured in the prefrontal-cortex, striatum and hippocampus. Hesperidin prevents and reverses ketamine-induced hyperactivities, social withdrawal and cognitive impairment. Also, hesperidin prevented and reversed ketamine-induced decrease in glutathione and superoxide-dismutase levels in the prefrontal-cortical, striatal and hippocampal brain regions in mice. Consequently, hesperidin attenuated ketamine-induced increase in malondialdehyde, nitrite levels and acetylcholinesterase activities in the prefrontal-cortex, striatum and hippocampus, respectively. The study showed that hesperidin prevents and reverses ketamine-induced schizophrenia-like behavior through inhibition of oxidative/nitrergic stress and acetylcholinesterase activity in mice brains. Therefore, these findings suggest that hesperidin dietary supplementation could provide natural nutritional intervention to protect against epigenetic-induced mental ill-health like schizophrenia, and thus serve as an important agent for nutritional psychiatry.

N, N-dimethylglycine Protects Behavioral Disturbances and Synaptic Deficits Induced by Repeated Ketamine Exposure in Mice.

Ketamine, an N-methyl-d-aspartate receptor (NMDAR) blocker, is gaining ground as a treatment option for depression. The occurrence of persistent psychosis and cognitive impairment after repeated use of ketamine remains a concern. N, N-dimethylglycine (DMG) is a nutrient supplement and acts as an NMDAR glycine site partial agonist. The objective of this study was to assess whether DMG could potentially prevent the behavioral and synaptic deficits in mice after repeated ketamine exposure. Male ICR mice received ketamine (20 mg/kg) from postnatal day (PN) 33-46, twice daily, for 14 days. The locomotor activity, novel location recognition test (NLRT), novel object recognition test (NORT), social interaction test, head twitch response induced by serotonergic hallucinogen, and the basal synaptic transmission and long-term potentiation (LTP) in the hippocampal slices were monitored after repeated ketamine treatment. Furthermore, the protective effects of repeated combined administration of DMG (30 and 100 mg/kg) with ketamine on behavioral abnormalities and synaptic dysfunction were assessed. The results showed that mice exhibited memory impairments, social withdrawal, increased head twitch response, reduced excitatory synaptic transmission, and lower LTP after repeated ketamine exposure. The ketamine-induced behavioral and synaptic deficits were prevented by co-treatment with DMG. In conclusion, these findings may pave a new path forward to developing a combination formula with ketamine and DMG for the treatment of depression and other mood disorders.

AT1 -R is involved in the development of long-lasting, region-dependent and oxidative stress-independent astrocyte morphological alterations induced by Ketamine.

Astrocytes play an essential role in the genesis, maturation and regulation of the neurovascular unit. Multiple evidence support that astrocyte reactivity has a close relationship to neurovascular unit dysfunction, oxidative stress and inflammation, providing a suitable scenario for the development of mental disorders. Ketamine has been proposed as a single-use antidepressant treatment in major depression, and its antidepressant effects have been associated with anti-inflammatory properties. However, Ketamine long-lasting effects over the neurovascular unit components remain unclear. Angiotensin II AT1 receptor (AT1 -R) blockers have anti-inflammatory, antioxidant and neuroprotective effects. The present work aims to distinguish the acute and long-term Ketamine effects over astrocytes response extended to other neurovascular unit components, and the involvement of AT1 -R, in prefrontal cortex and ventral tegmental area. Male Wistar rats were administered with AT1 -R antagonist Candesartan/Vehicle (days 1-10) and Ketamine/Saline (days 6-10). After 14 days drug-free, at basal conditions or after Ketamine Challenge, the brains were processed for oxidative stress analysis, cresyl violet staining and immunohistochemistry for glial, neuronal activation and vascular markers. Repeated Ketamine administration induced long-lasting region-dependent astrocyte reactivity and morphological alterations, and neuroadaptative changes observed as exacerbated oxidative stress and neuronal activation, prevented by the AT1 -R blockade. Ketamine Challenge decreased microglial and astrocyte reactivity and augmented cellular apoptosis, independently of previous treatment. Overall, AT1 -R is involved in the development of neuroadaptative changes induced by repeated Ketamine administration but does not interfere with the acute effects supporting the potential use of AT1 -R blockers as a Ketamine complementary therapy in mental disorders.

Genistein attenuates cognitive deficits and neuroapoptosis in hippocampus induced by ketamine exposure in neonatal rats.

Ketamine is a frequently used anesthetic in pediatric patients that can cause cognitive impairment. Genistein, a bioactive component of soy products, has been shown to suppress neuronal death through regulating the expression of apoptosis related genes. In this study, we hypothesized that genistein could alleviate ketamine-induced cognitive impairment by ameliorating hippocampal neuronal loss and tested this hypothesis in rats. Neonatal rats were treated with ketamine and genistein. Hippocampal tissue was harvested for histological and biochemical analysis to determine neuronal apoptosis and proteins involved in the apoptotic pathways. Behavioral assays including contextual fear conditioning test and Morris water maze test were performed to assess cognitive functions, including learning and memory. We found that in fear conditioning test, genistein restored freezing time in ketamine treated rats in a dose dependent manner. Similarly, genistein attenuated impaired learning and memory in Morris water maze test in rats treated with ketamine. Additionally, ketamine-induced neuronal apoptosis in rat hippocampus was attenuated by genistein treatment. Finally, we found that genistein partially restored proteins associated with apoptosis, including Bax, Bcl-2, cleaved caspase 3, and phosphorylated GSK-3ß and Akt. Genistein suppresses hippocampal neuronal loss and cognitive disruption induced by ketamine in rats.

Dietary zinc supplement militates against ketamine-induced behaviours by age-dependent modulation of oxidative stress and acetylcholinesterase activity in mice.

BACKGROUND: The potential differential modulatory effects of zinc-supplemented diet on ketamine-induced changes in behaviours, brain oxidative stress, acetylcholinesterase activity, and zinc (ZN) levels were examined in prepubertal and aged mice. METHODS: Aged and prepubertal mice were divided into 2 groups consisting of 80 aged and 80 prepubertal mice, each having 8 treatment groups of 10 animals each. The treatment groups are: vehicle control group (fed standard diet and given intraperitoneal {ip} normal saline), three groups fed ZN-supplemented diet (at 25, 50 and 100 mg/kg of feed) and given ip normal saline, ketamine control group (fed standard diet and given ip ketamine), and finally another three groups fed ZN-supplemented diet (at 25, 50 and 100 mg/kg of feed) and given ip ketamine. Intraperitoneal normal saline (at 2 ml/kg/day) or ketamine (at 30 mg/kg/day) were administered during the last 10 days of study. On day 60, animals were exposed to the open-field, Y-maze, radial-arm maze, and elevated plus maze following which they were euthanised; blood and brain homogenate were used for assessment of biochemical parameters. RESULTS: Zinc supplementation was associated with an increase in food intake and body weight (in both age groups), a reduction in ketamine-induced increase in locomotion, rearing and grooming, and significantly higher working-memory scores (compared to ketamine control). Also, there was a decrease in anxiety-related behaviours, enhanced antioxidant status, reduced lipid peroxidation, and reduced acetylcholinesterase activity. CONCLUSION: In conclusion, dietary ZN supplementation was associated with variable degrees of prevention of ketamine-induced changes, depending on the age of animals.

Modulations in the ATPases during ketamine-induced schizophrenia and regulatory effect of "3-(3, 4-dimethoxy phenyl) -1- (4-methoxyphenyl) prop-2-en-1-one": an in vivo and in silico studies.

Schizophrenia is a devastating illness and displays a wide range of psychotic symptoms. Accumulating evidence indicate impairment of bioenergetic pathways including energy storage and usage in the pathogenesis of schizophrenia. Although well-established synthetic drugs are being used for the management of schizophrenia, most of them have several adverse effects. Hence, natural products derived from medicinal plants represent a continuous major source for ethnomedicine-derived pharmaceuticals for different neurological disorders including schizophrenia. In the present study, we have investigated the neuroprotective effect of the novel bioactive compound i.e. "3-(3,4-dimethoxy phenyl) -1- (4-methoxyphenyl) prop-2-en-1-one" of Celastrus paniculata against ketamine-induced schizophrenia with particular reference to the activities of ATPase using in vivo and in silico methods. Ketamine-induced schizophrenia caused significant reduction in the activities of all three ATPases (Na+/K+, Ca2+ and Mg2+) in different regions of brain which reflects the decreased turnover of ATP, presumably due to the inhibition of oxidoreductase system and uncoupling of the same from the electron transport system. On par with the reference compound, clozapine, the activity levels of all three ATPases were restored to normal after pretreatment with the compound suggesting recovery of energy loss that was occurred during ketamine-induced schizophrenia. Besides, the compound has shown strong interaction and exhibited highest binding energies against all the three ATPases with a lowest inhibition constant value than the clozapine. The results of the present study clearly imply that the compound exhibit significant neuroprotective and antischizophrenic effect by modulating bioenergietic pathways that were altered during induced schizophrenia.

Blackberry extract improves behavioral and neurochemical dysfunctions in a ketamine-induced rat model of mania.

Bipolar disorder is a chronic mood disorder characterized by episodes of mania and depression. The aim of this study was to investigate the effects of blackberry extract on behavioral parameters, oxidative stress and inflammatory markers in a ketamine-induced model of mania. Animals were pretreated with extract (200 mg/kg, once a day for 14 days), lithium chloride (45 mg/kg, twice a day for 14 days), or vehicle. Between the 8th and 14th days, the animals received an injection of ketamine (25 mg/kg) or vehicle. On the 15th day, thirty minutes after ketamine administration, the animals' locomotion was assessed using open-field apparatus. After the experiments, the animals were euthanized and cerebral structures were removed for neurochemical analyses. The results showed that ketamine treatment induced hyperlocomotion and oxidative damage in the cerebral cortex, hippocampus and striatum. In contrast, pretreatment with the extract or lithium was able to prevent hyperlocomotion and oxidative damage in the cerebral cortex, hippocampus, and striatum. In addition, IL-6 and IL-10 levels were increased by ketamine, while the extract prevented these effects in the cerebral cortex. Pretreatment with the extract was also effective in decreasing IL-6 and increasing the level of IL-10 in the striatum. In summary, our findings suggest that blackberry consumption could help prevent or reduce manic episodes, since this extract have demonstrated neuroprotective properties as well as antioxidant and anti-inflammatory effects in the ketamine-induced mania model.

Traditional Chinese medicine, Kami-Shoyo-San protects ketamine-induced neurotoxicity in human embryonic stem cell-differentiated neurons through activation of brain-derived neurotrophic factor.

BACKGROUND: Anesthesia-induced neurotoxicity may cause permanent dysfunctions in human brains. In this work, we used a cell-based in-vitro model to demonstrate that traditional Chinese medicine, Kami-Shoyo-San may protect ketamine-induced neuronal apoptosis in human embryonic stem cell-differentiated neurons. METHODS: Human embryonic stem cell-differentiated neurons were cultured in vitro and treated with high-concentration ketamine to induce neuronal apoptosis. Pre-incubation of Kami-Shoyo-San was conducted to evaluate its neuroprotection on ketamine-injured neurons. Quantitative real-time PCR and western blot assays were used to assess brain-derived neurotrophic factor and its receptor, tropomyosin receptor kinase B, in response to Kami-Shoyo-San and ketamine treatment. Brain-derived neurotrophic factor/tropomyosin receptor kinase B signaling pathway was then deactivated, by siRNA application, to further explore its functional role in Kami-Shoyo-San-mediated protection on ketamine-induced apoptosis among human embryonic stem cell-differentiated neurons. RESULTS: High concentration of ketamine-induced significant apoptosis, whereas pre-incubation of Kami-Shoyo-San markedly rescued ketamine-induced apoptosis, in human embryonic stem cell-differentiated neurons. Kami-Shoyo-San activated brain-derived neurotrophic factor/tropomyosin receptor kinase B signaling pathway by upregulating brain-derived neurotrophic factor and inducing tropomyosin receptor kinase B phosphorylation. Conversely, siRNA-mediated brain-derived neurotrophic factor/tropomyosin receptor kinase B signaling pathway deactivation reversed the neuroprotection of Kami-Shoyo-San in ketamine-injured human embryonic stem cell-differentiated neurons. CONCLUSION: Kami-Shoyo-San could protect ketamine-induced neurotoxicity, and the underlying mechanism may involve brain-derived neurotrophic factor/tropomyosin receptor kinase B signaling pathway.

Evaluation of the Memory Enhancing Activity of Dichloromethane Fraction of the Methanolic Extract of Pycnanthus angolensis Stem Bark on Experimental Models of Memory Impairment.

Pycnanthus angolensis (Welw) Warb., Myristicaceae, is used extensively in ethnomedicine. Numerous health benefits have been ascribed to the use of different parts of P. angolensis including its role in cognitive function and inflammatory conditions. Hence, this study was undertaken to investigate the effect of stem bark of the plant on memory function in mice.The plant material was pulverized into powder and extracted by maceration with 80% methanol at room temperature for 48 h. This was subsequently fractionated using N-hexane, Dichloromethane (DCM) and Ethyl acetate. The Dichloromethane fraction which is the most potent fraction (25, 50 and 100 mg/kg) was evaluated for memory enhancing activity using the Y-maze (YMT), morris water maze (MWM) and the elevated plus maze (EPM) on D-galactose plus scopolamine and ketamine induced amnesia. The antioxidant markers and acetylcholinesterase (AChE) inhibiting effect of DCM were also investigated.The results obtained from the behavioural study indicates that the DCM fraction significantly (p<0.05) increased alternation behaviour of mice in the YMT, decreased the escape latency in the MWM paradigm and decreased the transfer latency in the EPM. Biochemically, DCM increased glutathione, and superoxide dismutase, but decreased malondialdehyde and AChE activity in the brain.The findings therefore suggests that the DCM possesses significant memory enhancing activity, which may be due to enhancement of antioxidant activity and cholinergic transmission. The attenuation of the effect of ketamine by the DCM may possibly result from an increase in NMDA receptor mediated neurotransmission and attenuation of oxidative stress.

Measuring the middle-ear reflex: A quantitative method to assess effects of industrial solvents on central auditory pathways.

Volatile organic solvents are frequently present in industrial atmospheres. Their lipophilic properties mean they quickly reach the brain following inhalation. Acute exposure to some solvents perturbs the middle ear reflex, which could jeopardize cochlear protection against loud noises. As the physiological mechanisms involved in this protective reflex are highly complex, in vivo rodent models are required to allow rapid and reliable identification of any adverse effects of solvents on the middle ear reflex (MER). In this study, MER amplitude was measured in anesthetized Brown-Norway rats by monitoring the decrease in distortion product otoacoustic emissions (DPOAEs) caused by a contralateral stimulation. Our screening test consisted in measuring the impact of inhalation of solvent vapors at 3000 ppm for 15 min on the MER amplitude. We had previously studied a selection of aromatic solvents with this model; here, we extended the analysis to volatile compounds from other chemical families. The results obtained shed light on the mechanisms involved in the interactions between solvents and their neuronal targets. Thus, benzene and chlorobenzene had the greatest effect on MER (≥ + 1.8 dB), followed by a group composed of toluene, styrene, p-xylene, m-xylene, tetrachloroethylene and cyclohexane, which had a moderate effect on the MER (between + 0.3 and + 0.7 dB). Finally, trichloroethylene, n-hexane, methyl-ethyl-ketone, acetone, o-xylene, and ethylbenzene had no effect on the MER. Thus, the effect of solvents on the MER is not simply linked to their lipophilicity, rather it depends on specific interactions with neuronal targets. These interactions appear to be governed by the compound's chemical structure, e.g. the presence of an aromatic ring and its steric hindrance. In addition, perturbation of the MER by a solvent is independent of its toxic effects on cochlear cells. As the MER plays a protective role against exposure to high-intensity noises, these findings could have a significant impact in terms of prevention for subjects exposed to both noise and solvents.

Long-Term Neurobehavioral Consequences of a Single Ketamine Neonatal Exposure in Rats: Effects on Cellular Viability and Glutamate Transport in Frontal Cortex and Hippocampus.

The neonatal exposure to general anesthetics has been associated with neuronal apoptosis and dendritic spines morphologic changes in the developing brain. Ketamine, a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist, is widely used in pediatric patients to induce general anesthesia, analgesia, and perioperative sedation. In the present study, we investigated short- and long-term effects of a single ketamine (20 mg/kg, s.c.) neonatal exposure at postnatal day 7 in rats on the hippocampal and frontal cortical cellular viability. Additionally, putative neurochemical alterations and neurobehavioral impairments were evaluated in the adulthood. Ketamine neonatal administration selectively decreased cellular viability in the hippocampus, but not in the frontal cortex, 24 h after the treatment. Interestingly, a single ketamine neonatal exposure prevented the vulnerability to glutamate-induced neurotoxicity in the frontal cortex of adult rats. No short- or long-term damage to cellular membranes, as an indicative of cell death, was observed in hippocampal or cortical slices. However, ketamine induced a long-term increase in hippocampal glutamate uptake. Regarding behavioral analysis, neonatal ketamine exposure did not alter locomotor activity and anxiety-related parameters evaluated in the open-field test. However, ketamine administration disrupted the hippocampal-dependent object recognition ability of adult rats, while improved the motor coordination addressed on the rotarod. These findings indicate that a single neonatal ketamine exposure induces a short-term reduction in the hippocampal, but not in cortical, cellular viability, and long-term alterations in hippocampal glutamate transport, improvement on motor performance, and short-term recognition memory impairment.

Protective effects of Spinacia oleracea seeds extract in an experimental model of schizophrenia: Possible behavior, biochemical, neurochemical and cellular alterations.

Schizophrenia is one of the psychotic mental disorders characterized by symptoms of thought, behavior, and social problems. Newer biomedicine and pharmacotherapy has been investigated for the treatment of various neuropsychiatric disorders in the past few decades. Spinacia oleracea is one of these, reported to have beneficial effect against several neurodegenerative disorders. The present study was carried to explore the protective effects of Spinacia oleracea seed extract (SOEE) in an experimental model of ketamine-induced schizophrenia in mice. Ketamine (50 mg/kg, i.p.) was used to induce stereotyped psychotic behavioural symptoms in mice. Behavioral studies (locomotor activity, stereotype behaviors, immobility duration and memory retention) were carried out to investigate the protective of SOEE on ketamine-induced psychotic symptoms, followed by biochemical, neurochemical and cellular alterations in the brain. Treatment with SOEE for 15 consecutive days significantly attenuated stereotyped behavioral symptoms in mice. Biochemical estimations revealed that SOEE reduced lipid peroxidation and restored total brain proteins. Furthermore, SOEE remarkably reduced dopamine levels, AChE activity & inflammatory surge (serum TNF-α) and increased the levels of GABA and reduced glutathione in mice. The outcomes of the study suggested that SOEE could ameliorate ketamine-induced psychotic symptoms in mice, indicating a protective effect in the treatment of schizophrenia.

The Evaluation of Folic Acid-Deficient or Folic Acid-Supplemented Diet in the Gestational Phase of Female Rats and in Their Adult Offspring Subjected to an Animal Model of Schizophrenia.

Although folic acid (FA) supplementation is known to influence numerous physiological functions, especially during pregnancy, little is known about its direct effects on the mothers' health. However, this vitamin is essential for the health of the mother and for the normal growth and development of the fetus. Thus, the aim of this study was (1) to evaluate the cognitive effects and biochemical markers produced by the AIN-93 diet (control), the AIN-93 diet supplemented with different doses of FA (5, 10, and 50 mg/kg), and a FA-deficient diet during pregnancy and lactation in female mother rats (dams) and (2) to evaluate the effect of maternal diets on inflammatory parameters in the adult offspring which were subjected to an animal model of schizophrenia (SZ) induced by ketamine (Ket). Our study demonstrated through the Y-maze test that rats subjected to the FA-deficient diet showed significant deficits in spatial memory, while animals supplemented with FA (5 and 10 mg/kg) showed no deficit in spatial memory. Our results also suggest that the rats subjected to the FA-deficient diet had increased levels of carbonylated proteins in the frontal cortex and hippocampus and also increased plasma levels of homocysteine (Hcy). Folate was able to prevent cognitive impairments in the rats supplemented with FA (5 and 10 mg/kg), data which may be attributed to the antioxidant effect of the vitamin. Moreover, FA prevented protein damage and elevations in Hcy levels in the rats subjected to different doses of this vitamin (5, 10, and 50 mg/kg). We verified a significant increase of the anti-inflammatory cytokine (interleukin-4 (IL-4)) and a reduction in the plasma levels of proinflammatory cytokines (interleukin-6 (IL-6)) and TNF-α) in the dams that were subjected to the diets supplemented with FA (5, 10, and 50 mg/kg), showing the possible anti-inflammatory effects of FA during pregnancy and lactation. In general, we also found that in the adult offspring that were subjected to an animal model of SZ, FA had a protective effect in relation to the levels of IL-4, IL-6, and TNF-α, which indicates that the action of FA persisted in the adult offspring, since FA showed a lasting effect on the inflammatory response, which was similar in both the dams and their offspring. In conclusion, the importance of supplementation with FA during pregnancy and lactation should be emphasized, not only for the benefit of the offspring but also for the health of the mother. All this is due to the considerable protective effect of this vitamin against oxidative damage, cognitive impairment, hyperhomocysteinemia, immune function, and also its ability in preventing common processes in post-pregnancy stages, as well as in reducing the risks of neurodevelopmental disorders and enhancing fetal immune development.

Development of a Functional Observational Battery in the Minipig for Regulatory Neurotoxicity Assessments.

A functional observational battery (FOB) is recommended as the first-tier neurotoxicity screening in the preclinical safety pharmacology testing guidelines. Minipigs have increasingly been used in regulatory toxicology studies; however, no current FOB protocol is available for neurotoxicity testing in these species. Hence, a minipig FOB instrument was developed. A complete crossover study with Sinclair minipigs was performed to evaluate physiologic, neurologic, and behavioral effects of amphetamine, ketamine, and diazepam. The treated minipigs were first observed in their home cage, were video-recorded for 10 minutes in an open field, and then went through a complete neurologic examination. Both ketamine and diazepam were shown to reduce the freezing and behavior shifts of treated minipigs, while increasing their exploratory behaviors. Both drugs also caused muscular and gait impairment. The effects of ketamine and diazepam were consistent with their roles as central nervous system (CNS) suppressants. Unique effects were also observed with ketamine and diazepam treatments, which may reflect their unique mechanisms of action. Consistent with its role as a CNS stimulant, amphetamine caused the treated minipigs to be hyperactive and to display increased freezing and behavior shifts and reduced exploring activities. These effects of amphetamine were opposite to those observed with ketamine and diazepam. Amphetamine also increased locomotion in the treated minipigs. The present effects of amphetamine, ketamine, and diazepam are in agreement with observations by others. In conclusion, the minipig is a suitable species for FOB evaluation of pharmaceuticals in preclinical safety pharmacology testing.

Decreased Thalamocortical Connectivity in Chronic Ketamine Users.

Disintegration in thalamocortical integration suggests its role in the mechanistic 'switch' from recreational to dysregulated drug seeking/addiction. In this study, we aimed to address whether thalamic nuclear groups show altered functional connectivity within the cerebral cortex in chronic ketamine users. One hundred and thirty subjects (41 ketamine users and 89 control subjects) underwent rsfMRI (resting-state functional Magnetic Resonance Imaging). Based on partial correlation functional connectivity analysis we partitioned the thalamus into six nuclear groups that correspond well with human histology. Then, in the area of each nuclear group, the functional connectivity differences between the chronic ketamine user group and normal control group were investigated. We found that the ketamine user group showed significantly less connectivity between the thalamic nuclear groups and the cortical regions-of-interest, including the prefrontal cortex, the motor cortex /supplementary motor area, and the posterior parietal cortex. However, no increased thalamic connectivity was observed for these regions as compared with controls. This study provides the first evidence of abnormal thalamocortical connectivity of resting state brain activity in chronic ketamine users. Further understanding of pathophysiological mechanisms of the thalamus in addiction (ketamine addiction) may facilitate the evaluation of much-needed novel pharmacological agents for improved therapy of this complex disease.

Effect of folic acid on oxidative stress and behavioral changes in the animal model of schizophrenia induced by ketamine.

Recent studies have shown benefits for the supplementation of folic acid in schizophrenic patients. The aim of this study was to evaluate the effects of folic acid addition on adult rats, over a period of 7 or 14 days. It also sets out to verify any potential protective action using an animal model of schizophrenia induced by ketamine, in behavioral and biochemical parameters. This study used two protocols (acute and chronic) for the administration of ketamine at a dose of 25 mg/kg (i.p.). The folic acid was given by oral route in doses of 5, 10 and 50 mg/kg, once daily, for 7 and/or 14 days in order to compare the protective effects of folic acid. Thirty minutes after the last administration of ketamine, the locomotor and social interaction activities were evaluated, and immediately the brain structure were removed for biochemical analysis. In this study, ketamine was administered in a single dose or in doses over the course of 7 days increasing the animal's locomotion. This study showed that the administration of folic acid over 7 days was unable to prevent hyper locomotion. In contrast, folic acid (10 and 50 mg/kg) administrated over a period of 14 days, was able to partially prevent the hyper locomotion. Our data indicates that both acute and chronic administrations of ketamine increased the time to first contact between the animals, while the increased latency for social contact was completely prevented by folic acid (5, 10 and 50 mg/kg). Chronic and acute administrations of ketamine also increased lipid peroxidation and protein carbonylation in brain. Folic acid (10 and 50 mg/kg) supplements showed protective effects on the oxidative damage found in the different brain structures evaluated. All together, the results indicate that nutritional supplementation with folic acid provides promising results in an animal model of schizophrenia induced by ketamine.

Neuroprotective effects of the ethanol stem bark extracts of Terminalia ivorensis in ketamine-induced schizophrenia-like behaviors and oxidative damage in mice.

CONTEXT: Schizophrenia is a heterogenous neurological disorder, which has been hypothetically linked to oxidative imbalance and associated behavioral perturbations. Preliminary evidence from animal models predictive of human psychosis suggests that Terminalia ivorensis A. Chev. (Combretaceae) has antipsychotic-like activity in mice. OBJECTIVE: This study investigates the neuroprotective property of the ethanol stem bark extracts of T. ivorensis (EETI) in reversal treatment of ketamine-induced schizophrenia-like behaviors and oxidative alteration in adult male Swiss albino mice. MATERIALS AND METHODS: Animals were divided into six treatment groups (n = 5). Animals received distilled water or ketamine (20 mg/kg) once daily intraperitoneally (i.p.) for 14 days, and from the 8th to the 14th day, they were treated with EETI (125, 250 or 500 mg/kg), risperidone (RIS) or vehicle orally once daily. Behaviors related to positive (locomotor activity) and cognitive (Y maze) symptoms of schizophrenia were assessed. Glutathione (GSH) levels, superoxide dismutase (SOD) and catalase (CAT) activities, including malondialdehyde (MDA) concentration were measured in mice whole brains. RESULT: The LD50 of EETI was 2236.06 mg/kg, p.o. body weight. EETI (125, 250 or 500 mg/kg, p.o.) demonstrated significant (p < 0.05) inhibition of ketamine-induced hyperlocomotion and cognitive dysfunction. The extract decreased MDA concentration (39.0, 62.6 and 67.5%) in a dose-dependent manner. Moreover, EETI significantly (p < 0.05) reversed the depletion of GSH, and increased activities of SOD and CAT in brain tissues. DISCUSSION AND CONCLUSION: These findings suggest that EETI probably exert its antipsychotic-like activity, via a neuroprotective compensatory mechanism of action, and as such, could be relevant in the management of schizophrenia.

Electrophysiological alterations in a complex rat model of schizophrenia.

BACKGROUND: Psychiatric disorders are frequently accompanied by changes in brain electrical oscillations and abnormal auditory event related potentials. The goal of this study was to characterize these parameters of a new rat substrain showing several alterations related to schizophrenia. METHODS: Male rats of the new substrain, developed by selective breeding after combined subchronic ketamine treatment and postweaning social isolation, and naive Wistar ones group-housed without any interventions were involved in the present study. At the age of 3 months, animals were implanted with cortical electroencephalography electrodes. Auditory evoked potentials during paired-click stimuli and power of oscillation in different frequency bands were determined with and without acute ketamine (20mg/kg) treatment. RESULTS: Regarding the auditory evoked potentials, the latency of P2 was delayed and the amplitude of N1 peak was lower in the new substrain. The new substrain showed increased power of oscillations in the theta, alpha and beta bands, while decreased power was detected in delta and gamma2 bands (52-70Hz) compared with control animals. Acute ketamine treatment increased the gamma1 band (30-48Hz) power in both groups, while it elicited significant changes only in the new substrain in the total power and in alpha, beta and gamma2 bands. CONCLUSIONS: The validation of the translational utility of this new rat substrain by electrophysiological investigations revealed that these rats show abnormalities that may model a part of the neurophysiological deficits observed in schizophrenia.

Only extra-high dose of ketamine affects l-glutamate-induced intracellular Ca(2+) elevation and neurotoxicity.

The neurotoxic effects of anesthetics on the developing brain are a concern. Although most of the anesthetics are GABAA agonists or NMDA antagonists, the differences in these effects on prospective glutamate-neurotoxicity in the brain is not fully understood. We examined the degree of L-glutamate-induced intracellular calcium ([Ca(2+)]i) elevation and neurotoxicity in neurons exposed to anesthetics. Primary cortical neurons from E17 rats were preincubated with 1-100 µM of ketamine or thiopental sodium (TPS) for the first 72 h of culturing. Two weeks later, the neurons were exposed to L-glutamate. The extent of glutamate toxicity was evaluated using Ca(2+)-imaging and morphological experiments. Preincubation with 100 µM ketamine but not with other concentrations of ketamine and TPS for the first 72 h in culture significantly enhanced L-glutamate-induced [Ca(2+)]i elevation 2 weeks later. Morphology experiments showed that vulnerability to L-glutamate-mediated neurotoxicity was only altered in neurons preincubated with 100 µM ketamine but not with TPS. Although preincubation with high concentration of ketamine showed enhancement of L-glutamate-induced [Ca(2+)]i elevation 2 weeks later, long-term exposure to TPS or ketamine at clinical doses during developmental periods may not result in a dose-related potentiation of exogenous glutamate-induced neurotoxicity, once the intravenous anesthetics are discontinued.