Prenatal MAM exposure raises kynurenic acid levels in the prefrontal cortex of adult rats.

BACKGROUND: Elevated brain levels of kynurenic acid (KYNA), a metabolite in the kynurenine pathway, are associated with cognitive dysfunctions, which are nowadays often considered as fundamental characteristics of several psychopathologies; however, the role of KYNA in mental illnesses, such as schizophrenia, is not fully elucidated. This study aimed to assess KYNA levels in the prefrontal cortex (PFC) of rats prenatally treated with methylazoxymethanol (MAM) acetate, i.e., a well-validated neurodevelopmental animal model of schizophrenia. The effects of an early pharmacological modulation of the endogenous cannabinoid system were also evaluated. METHODS: Pregnant Sprague-Dawley rats were treated with MAM (22 mg/kg, ip) or its vehicle at gestational day 17. Male offspring were treated with the cannabinoid CB1 receptor antagonist/inverse agonist AM251 (0.5 mg/kg/day, ip) or with the typical antipsychotic haloperidol (0.6 mg/kg/day, ip) from postnatal day (PND) 19 to PND39. The locomotor activity and cognitive performance were assessed in the novel object recognition test and the open field test in adulthood. KYNA levels in the PFC of prenatally MAM-treated rats were also assessed. RESULTS: A significant cognitive impairment was observed in prenatally MAM-treated rats (p < 0.01), which was associated with enhanced PFC KYNA levels (p < 0.05). The peripubertal AM251, but not haloperidol, treatment ameliorated the cognitive deficit (p < 0.05), by normalizing the PFC KYNA content in MAM rats. CONCLUSIONS: The present findings suggest that the cognitive deficit observed in MAM rats may be related to enhanced PFC KYNA levels which could be, in turn, mediated by the activation of cannabinoid CB1 receptor. These results further support the modulation of brain KYNA levels as a potential therapeutic strategy to ameliorate the cognitive dysfunctions in schizophrenia.

CNS autoimmune response in the MAM/pilocarpine rat model of epileptogenic cortical malformation.

The development of seizures in epilepsy syndromes associated with malformations of cortical development (MCDs) has traditionally been attributed to intrinsic cortical alterations resulting from abnormal network excitability. However, recent analyses at single-cell resolution of human brain samples from MCD patients have indicated the possible involvement of adaptive immunity in the pathogenesis of these disorders. By exploiting the MethylAzoxyMethanol (MAM)/pilocarpine (MP) rat model of drug-resistant epilepsy associated with MCD, we show here that the occurrence of status epilepticus and subsequent spontaneous recurrent seizures in the malformed, but not in the normal brain, are associated with the outbreak of a destructive autoimmune response with encephalitis-like features, involving components of both cell-mediated and humoral immune responses. The MP brain is characterized by blood-brain barrier dysfunction, marked and persisting CD8+ T cell invasion of the brain parenchyma, meningeal B cell accumulation, and complement-dependent cytotoxicity mediated by antineuronal antibodies. Furthermore, the therapeutic treatment of MP rats with the immunomodulatory drug fingolimod promotes both antiepileptogenic and neuroprotective effects. Collectively, these data show that the MP rat could serve as a translational model of epileptogenic cortical malformations associated with a central nervous system autoimmune response. This work indicates that a preexisting brain maldevelopment predisposes to a secondary autoimmune response, which acts as a precipitating factor for epilepsy and suggests immune intervention as a therapeutic option to be further explored in epileptic syndromes associated with MCDs.

Sex differences in neuronal oscillatory activity and memory in the methylazoxymethanol acetate model of schizophrenia.

The methylazoxymethanol acetate (MAM) rodent model is used to study aspects of schizophrenia. However, numerous studies that have employed this model have used only males, resulting in a dearth of knowledge on sex differences in brain function and behaviour. The purpose of this study was to determine whether differences exist between male and female MAM rats in neuronal oscillatory function within and between the prefrontal cortex (PFC), ventral hippocampus (vHIP) and thalamus, behaviour, and in proteins linked to schizophrenia neuropathology. We showed that female MAM animals exhibited region-specific alterations in theta power, elevated low and high gamma power in all regions, and elevated PFC-thalamus high gamma coherence. Male MAM rats had elevated beta and low gamma power in PFC, and elevated vHIP-thalamus coherence. MAM females displayed impaired reversal learning whereas MAM males showed impairments in spatial memory. Glycogen synthase kinase-3 (GSK-3) was altered in the thalamus, with female MAM rats displaying elevated GSK-3α phosphorylation. Male MAM rats showed higher expression and phosphorylation GSK-3α, and higher expression of GSK-ß. Sex-specific changes in phosphorylated Tau levels were observed in a region-specific manner. These findings demonstrate there are notable sex differences in behaviour, oscillatory network function, and GSK-3 signaling in MAM rats, thus highlighting the importance of inclusion of both sexes when using this model to study schizophrenia.

Early developmental changes in a rat model of malformations of cortical development: Abnormal neuronal migration and altered response to NMDA-induced excitotoxic injury.

Malformations of cortical development (MCDs) are caused by abnormal neuronal migration processes during the fetal period and are a major cause of intractable epilepsy in infancy. However, the timing of hyperexcitability or epileptogenesis in MCDs remains unclear. To identify the early developmental changes in the brain of the MCD rat model, which exhibits increased seizure susceptibility during infancy (P12-15), we analyzed the pathological changes in the brains of MCD model rats during the neonatal period and tested NMDA-induced seizure susceptibility. Pregnant rats were injected with two doses of methylazoxymethanol acetate (MAM, 15 mg/kg, i.p.) to induce MCD, while controls were administered normal saline. The cortical development of the offspring was measured by performing magnetic resonance imaging (MRI) on postnatal days (P) 1, 5, and 8. At P8, some rats were sacrificed for immunofluorescence, Golgi staining, and Western analysis. In another set of rats, the number and latency to onset of spasms were monitored for 90 min after the NMDA (5 mg/kg i.p.) injection at P8. In MCD rats, in vivo MR imaging showed smaller brain volume and thinner cortex from day 1 after birth (p < 0.001). Golgi staining and immunofluorescence revealed abnormal neuronal migration, with a reduced number of neuronal cell populations and less dendritic arborization at P8. Furthermore, MCD rats exhibited a significant reduction in the expression of NMDA receptors and AMPAR4, along with an increase in AMPAR3 expression (p < 0.05). Although there was no difference in the latency to seizure onset between MCD rats and controls, the MCD rats survived significantly longer than the controls. These results provide insights into the early developmental changes in the cortex of a MCD rat model and suggest that delayed and abnormal neuronal development in the immature brain is associated with a blunted response to NMDA-induced excitotoxic injury. These developmental changes may be involved in the sudden onset of epilepsy in patients with MCD or prenatal brain injury.

Olanzapine, but not haloperidol, exerts pronounced acute metabolic effects in the methylazoxymethanol rat model.

AIM: Widely used second-generation antipsychotics are associated with adverse metabolic effects, contributing to increased cardiovascular mortality. To develop strategies to prevent or treat adverse metabolic effects, preclinical models have a clear role in uncovering underlying molecular mechanisms. However, with few exceptions, preclinical studies have been performed in healthy animals, neglecting the contribution of dysmetabolic features inherent to psychotic disorders. METHODS: In this study, methylazoxymethanol acetate (MAM) was prenatally administered to pregnant Sprague-Dawley rats at gestational day 17 to induce a well-validated neurodevelopmental model of schizophrenia mimicking its assumed pathogenesis with persistent phenotype. Against this background, the dysmetabolic effects of acute treatment with olanzapine and haloperidol were examined in female rats. RESULTS: Prenatally MAM-exposed animals exhibited several metabolic features, including lipid disturbances. Half of the MAM rats exposed to olanzapine had pronounced serum lipid profile alteration compared to non-MAM controls, interpreted as a reflection of a delicate MAM-induced metabolic balance disrupted by olanzapine. In accordance with the drugs' clinical metabolic profiles, olanzapine-associated dysmetabolic effects were more pronounced than haloperidol-associated dysmetabolic effects in non-MAM rats and rats exposed to MAM. CONCLUSION: Our results demonstrate metabolic vulnerability in female prenatally MAM-exposed rats, indicating that findings from healthy animals likely provide an underestimated impression of metabolic dysfunction associated with antipsychotics. In the context of metabolic disturbances, neurodevelopmental models possess a relevant background, and the search for adequate animal models should receive more attention within the field of experimental psychopharmacology.

Aberrant Hippocampal Development in Early-onset Mental Disorders and Promising Interventions: Evidence from a Translational Study.

Early-onset mental disorders are associated with disrupted neurodevelopmental processes during adolescence. The methylazoxymethanol acetate (MAM) animal model, in which disruption in neurodevelopmental processes is induced, mimics the abnormal neurodevelopment associated with early-onset mental disorders from an etiological perspective. We conducted longitudinal structural magnetic resonance imaging (MRI) scans during childhood, adolescence, and adulthood in MAM rats to identify specific brain regions and critical windows for intervention. Then, the effect of repetitive transcranial magnetic stimulation (rTMS) intervention on the target brain region during the critical window was investigated. In addition, the efficacy of this intervention paradigm was tested in a group of adolescent patients with early-onset mental disorders (diagnosed with major depressive disorder or bipolar disorder) to evaluate its clinical translational potential. The results demonstrated that, compared to the control group, the MAM rats exhibited significantly lower striatal volume from childhood to adulthood (all P <0.001). In contrast, the volume of the hippocampus did not show significant differences during childhood (P >0.05) but was significantly lower than the control group from adolescence to adulthood (both P <0.001). Subsequently, rTMS was applied to the occipital cortex, which is anatomically connected to the hippocampus, in the MAM models during adolescence. The MAM-rTMS group showed a significant increase in hippocampal volume compared to the MAM-sham group (P <0.01), while the volume of the striatum remained unchanged (P >0.05). In the clinical trial, adolescents with early-onset mental disorders showed a significant increase in hippocampal volume after rTMS treatment compared to baseline (P <0.01), and these volumetric changes were associated with improvement in depressive symptoms (r = - 0.524, P = 0.018). These findings highlight the potential of targeting aberrant hippocampal development during adolescence as a viable intervention for early-onset mental disorders with neurodevelopmental etiology as well as the promise of rTMS as a therapeutic approach for mitigating aberrant neurodevelopmental processes and alleviating clinical symptoms.

Las cícadas y su relación con algunas enfermedades neurodegenerativas / Cycads and their association with certain neurodegenerative diseases

Introducción: Las cícadas son plantas que en algunas partes del mundo son empleadas como alimento fresco o materia prima para la elaboración de harina con alto valor nutricional. Sin embargo, contienen principios activos como metilazoximetanol, β-metilamino-L-alanina, β-oxalilamino-L-alanina y cicasina, entre otros, que pueden producir efectos neurotóxicos. El consumo de cícadas y sus derivados se ha asociado con enfermedades neurodegenerativas, como el complejo demencia-parkinsonismo-esclerosis-lateral amiotrófica y otras enfermedades caracterizadas por alteraciones en la motricidad. Por lo tanto, no debemos perder de vista que todo producto, aunque sea de origen natural, puede ser benéfico o perjudicial para la salud, lo cual dependerá de sus componentes químicos y de la vulnerabilidad de quienes los consumen. Desarrollo: Se realizó un análisis de la literatura sobre las propiedades neurotóxicas de las cícadas y su asociación con enfermedades neurológicas, con el fin de proporcionar información estructurada a la población para contribuir a la prevención de problemas de salud en quienes interactúan con estas plantas. Conclusión: Las cícadas contienen neurotóxicos que contribuyen al desarrollo de enfermedades neurológicas cuando son ingeridas inadecuadamente, por lo que debemos considerar que si bien algunos vegetales pueden tener un alto valor nutricional y subsanar el déficit alimentario en las poblaciones vulnerables, también pueden ser tóxicos e impactar negativamente sobre la salud

Introduction: Cycads are ornamental plants that in some parts of the world are used as fresh food or raw material for producing flour with a high nutritional value. However, they also contain active compounds, including methylazoxymethanol, β-methylamino-L-alanine, β-alanine-L-oxalylamino and cycasin, which may produce neurotoxic effects. Some studies have associated consuming cycads and their derivatives with neurodegenerative diseases such as amyotrophic lateral sclerosis/Parkinsonism dementia complex, and other diseases characterised by motor impairment. Therefore, we must not forget that any product, no matter how natural, may present health risks or benefits depending on the chemical compounds it contains and the susceptibility of those who consume it. Development: We completed a literature analysis to evaluate the neurotoxic properties of cycads and their association with neurological diseases in order to provide structured scientific information that may contribute to preventing health problems in people who use these plants. Conclusion: Cycads contain neurotoxic compounds that may contribute to the development of neurological diseases when ingested improperly. We must be mindful of the fact that while some plants have a high nutritional value and may fill the food gap for vulnerable populations, they can also be toxic and have a negative impact on health

El tratamiento con progesterona previene las alteraciones motoras inducidas por la intoxicación con semillas de cícada (Dioon spinulosum) en la rata macho / Treatment with progesterone prevented the motor impairment induced by poisoning with seeds of Cicada (Dioon spinulosum) in the male rat

El consumo crónico de semillas de cícadas ha sido asociado con enfermedades neurodegenerativas, las cuales predominan en el género masculino. En México, las semillas decícada (Dioon spinulosum) son usadas como sustituto de maíz y a nivel experimental producen un déficit motor; probablemente causado por sus componentes neurotóxicos. En este sentido, la progesterona ejerce efectos neuroprotectores contra traumatismo cerebral, hipoxia, así como la muerte neuronal inducida por colchicina en el SNC; por lo que podría prevenir los efectos neurotóxicos producidos por el consumo crónico de semillas de Dioon spinulosum en ratas, una posibilidad explorada en el presente estudio. Se emplearon 32 ratas macho de la cepa Wistar distribuidas en cuatro grupos: a) un grupo control recibió 1 ml de agua purificada (v.o.) y 0,2 ml de aceite de maíz (s.c.); b) un grupo cícada recibió 5g/kg de la semilla de cícada (v.o.) y 0,2 ml de aceite de maíz (s.c.); c) un grupo más recibió 1 ml de agua purificada (v.o.) y 3 mg/kg de progesterona (s.c.); y d) el último grupo recibió semilla de cícada y progesterona. Los tratamientos fueron administrados diariamente durante 40 días y el efecto fue evaluado en las pruebas de actividad locomotora y nado forzado a los 20, 30 y 40 días de tratamiento. El grupo cícada redujo el número de cuadros cruzados en la prueba de actividad locomotora. En la prueba de nado forzado, los animales tratados con la semilla de cícada fueron los únicos que presentaron la conducta de giro, un efecto que fue prevenido por el tratamiento previo con progesterona. La administración de vehículo y progesterona no produjo per se la conducta de giro. En conclusión, la progesterona previene las alteraciones motoras inducidas por el consumo crónico de semillas de cícada en ratas forzadas a nadar (AU)

The chronic consumption of cycad seeds has been associated with neurodegenerative diseases, which are predominant in masculine gender. In Mexico, the cycad seeds (Dioon spinulosum) are used as a maize substitute and at experimental level produce a motor deficit; probably caused by its neurotoxic compounds. Progesterone could prevent the neurotoxic effects against traumatic brain injury, hypoxia and neuronal death induced by colchicine in the CNS. In addition, progesterone could prevent these neurotoxic effects produced by the chronic administration of cycad seeds (Dioon spinulosum) in rats, a possibility explored in the present study. Male wistar rats were randomly divided in 4 groups: a) a control group received 1 ml purified water (PO) and oil (0.2 ml, s.c.);b) a cycad group received a cycad seed 5g/kg (PO) and oil (0.2 ml,s.c.); c) another group received 1 ml of purified water (PO) and progesterone (3mg/kg, s.c.) and d) the last group received cycad seed and progesterone. All treatments were administered daily during 40 days and the effect was evaluated in behavioral tests (open filed and forced swim) were conducted on 20, 30 and 40 days of treatment. The cycad group decreased the number of squares crossed in the open field whereas, in the forced swim test, rotational behavior was only observed in the group administered with cycad seeds, this effect was prevented by previous progesterone treatment. The vehicle and progesterone administration did not produce the rotational behavior per se. In conclusion, progesterone prevents the motor deficit induced by the chronic consumption of cycad seeds in forced swim rats (AU)

Determination of macrozamin in Rhizoma Heterosmilacis Japonicae by RP-HPLC / 中国中药杂志

<p><b>OBJECTIVE</b>To develop a RP-HPLC method for the determination of the content of macrozamin in Rhizoma Heterosmilacis Japonicae.</p><p><b>METHOD</b>A Century C18 AQ column (4.6 mm x 250 mm, 5 microm) was used with the mobile phase consisted of water (4:96). The flow rate was 1.0 mL x min(-1). The detection wavelength was set at 215 nm, and the column temperature was 35 degrees C.</p><p><b>RESULT</b>The calibration curve was linear (r = 0.999 8) in the range of 19.12 - 382.4 microg x mL(-1) for macrozamin, the average recovery of the method was 99.5%, with RSD 2.1% (n = 9).</p><p><b>CONCLUSION</b>This method can be used for the quality study of Rhizoma Heterosmilacis Japonicae.</p>

Effects of Ethosuximide on the Pilocarpine Induced Seizure in Rat Model of Neuronal Migration Disorder

Cortical malformation-associated epileptic seizures are resistant to conventional anticonvulsant drugs. Relatively little research has been conducted on the effects of antiepileptic drugs (AEDs) on seizure activity in a rat model of dysplasia. We have used rats exposed to methylazoxymethanol acetate (MAM) in utero, an animal model featuring nodular heterotopia, to investigate the effects of ethosuximide (ETX) in the dysplastic brain. Pilocarpine was used to induce acute seizure in MAM-exposed and age-matched vehicle-injected control animals. Field potential recordings were used to monitor the amplitude and number of population spikes, and paired pulse inhibition in response to stimulation of the commissural pathway. Pharmaco-resistance was tested by measuring seizure latencies after pilocarpine administration (320 mg/kg, i.p.) with and without pre-treatment with ETX. Pre-treatment with 300 mg of ETX significantly prolonged the latency to the status epilepticus (SE) in both control and MAM-treated groups. Pre-treatment with ETX 100mg and ETX 200 mg had little effect in MAM-exposed rats. However, ETX 200 mg prolonged the latency to the SE in control groups. Spontaneous field potential and secondary after-discharges were higher for MAM-treated rat in comparison with control rats injects with ETX. The main findings of this study are that acute seizures initiated in MAM-exposed rats are relatively resistant to standard ETX assessed in vivo. These data suggest that ETX do not prolong seizure latencies in MAM-rats exposed to pilocarpine.