Maternal Separation Stress Affects Voluntary Ethanol Intake in a Sex Dependent Manner

Maternal separation (MS) stress is a predictive animal model for evaluating the effects of early stress exposure on alcohol use disorders (AUD). The extended amygdala (AMY) is a complex circuit involved in both stress- and ethanol-related responses. We hypothesized that MS stress may increase ethanol consumption in adulthood, as well as augment neuronal activity in extended AMY, in a sex-dependent manner. We aimed to investigate the influence of MS stress on the ethanol consumption of male and female mice, and the involvement of extended amygdala sub-nuclei in this process. The C57BL/6J pups were subjected to 180min of MS, from postnatal day (PND) 1 to 14. The control group was left undisturbed. On PND 45, mice (n=28) in cages were exposed to a bottle containing 20% ethanol (w/v) for 4h during the dark period of the light-dark cycle, for 3weeks. Afterward, mice underwent ethanol self-administration training in operant chambers under fixed ratio (FR) schedule. Then, subjects were tested under 2h sessions of a progressive-ratio (PR) schedule of reinforcement (the last ratio achieved was considered the breaking point), and at the end, a 4h session of FR schedule (binge-intake). An immunohistochemistry assay for Fos protein was performed in Nucleus Accumbens (NAcc), Bed Nucleus of Stria Terminalis (BNST), and AMY. Our results showed that in the third week of training, the female MS group consumed more ethanol than the respective control group. The MS group presented increased breakpoint parameters. Female control group and male MS group were more resistant to bitter quinine taste. Increased Fos-immunoreactive neurons (Fos-IR) were observed in the central nucleus of AMY, but not in NAcc nor BNST in male maternal-separated mice. Maternal separation stress may influence ethanol intake in adulthood, and it is dependent on the sex and reinforcement protocol.

Is Cannabidiol During Neurodevelopment a Promising Therapy for Schizophrenia and Autism Spectrum Disorders?

Schizophrenia and autism spectrum disorders (ASD) are psychiatric neurodevelopmental disorders that cause high levels of functional disabilities. Also, the currently available therapies for these disorders are limited. Therefore, the search for treatments that could be beneficial for the altered course of the neurodevelopment associated with these disorders is paramount. Preclinical and clinical evidence points to cannabidiol (CBD) as a promising strategy. In this review, we discuss clinical and preclinical studies on schizophrenia and ASD investigating the behavioral, molecular, and functional effects of chronic treatment with CBD (and with cannabidivarin for ASD) during neurodevelopment. In summary, the results point to CBD's beneficial potential for the progression of these disorders supporting further investigations to strengthen its use.

Blockade of GluN2B-containing NMDA receptors reduces short-term brain damage induced by early-life status epilepticus

Status epilepticus (SE) during developmental periods can cause short- and long-term consequences to the brain. Brain damage induced by SE is associated to NMDA receptors (NMDAR)-mediated excitotoxicity. This study aimed to investigate whether blockade of GluN2B-containing NMDAR is neuroprotective against SE-induced neurodegeneration and neuroinflammation in young rats. Forty-eight Wistar rats (16 days of life) were injected with pilocarpine (60 mg/kg; i.p.) 12-18 h after LiCl (3 mEq/kg; i.p.). Fifteen minutes after pilocarpine administration, animals received i.p. injections of saline solution (0.9% NaCl; SE + SAL group), ketamine (a non-selective and noncompetitive NMDAR antagonist; 25 mg/kg; SE + KET), CI-1041 (a GluN2B-containing NMDAR antagonist; 10 mg/kg; SE + CI group) or CP-101,606 (a NMDAR antagonist with great selectivity for NMDAR composed by GluN1/GluN2B diheteromers; 10 mg/kg; SE + CP group). Seven days after SE, brains were removed for Fluoro-Jade C staining and Iba1/ED1 immunolabeling. GluN2B-containing NMDAR blockade by CI-1041 or CP-101,606 did not terminate LiCl-pilocarpine-induced seizures. SE + SAL group presented intense neurodegeneration and Iba1⁺/ED1⁺ double-labeling in hippocampus (CA1 and dentate gyrus; DG) and amygdala (MePV nucleus). Administration of CP-101,606 did not alter this pattern. However, GluN2B-containing NMDAR blockade by CI-1041 reduced neurodegeneration and Iba1⁺/ED1⁺ double-labeling in hippocampus and amygdala similar to the reduction observed for SE + KET group. Our results indicate that GluN2B-containing NMDAR are involved in SE-induced neurodegeneration and microglial recruitment and activation, and suggest that stopping epileptic activity is not a condition required to prevent short-term brain damage in young animals.

Influence of environmental enrichment vs. time-of-day on behavioral repertoire of male albino Swiss mice

Environmental enrichment (EE) is a non-pharmacological manipulation that promotes diverse forms of benefits in the central nervous system of captive animals. It is thought that EE influences animal behavior in a specie-(strain)-specific manner. Since rodents in general present different behaviors during distinct periods of the day, in this study we aimed to investigate the influence of time-of-day on behavioral repertoire of Swiss mice that reared in EE. Forty male Swiss mice (21days old) were housed in standard (SC) or enriched conditions (EC) for 60days. Behavioral assessments were conducted during the light phase (in presence of light) or dark phase (in absence of light) in the following tasks: open field, object recognition and elevated plus maze. First, we observed that the locomotor and exploratory activities are distinct between SC and EC groups only during the light phase. Second, we observed that "self-protective behaviors" were increased in EC group only when mice were tested during the light phase. However, "less defensive behaviors" were not affected by both housing conditions and time-of-day. Third, we showed that the performance of EE animals in object recognition task was improved in both light and dark conditions. Our findings highlight that EE-induced alterations in exploratory and emotional behaviors are just evident during light conditions. However, EE-induced cognitive benefits are remarkable even during dark conditions, when exploratory and emotional behaviors were similar between groups.

Adenosine A(2A) receptors are necessary and sufficient to trigger memory impairment in adult mice

BACKGROUND AND PURPOSE

Caffeine (a non-selective adenosine receptor antagonist) prevents memory deficits in aging and Alzheimer's disease, an effect mimicked by adenosine A2 A receptor, but not A1 receptor, antagonists. Hence, we investigated the effects of adenosine receptor agonists and antagonists on memory performance and scopolamine-induced memory impairment in mice.

EXPERIMENTAL APPROACH

We determined whether A2 A receptors are necessary for the emergence of memory impairments induced by scopolamine and whether A2 A receptor activation triggers memory deficits in naïve mice, using three tests to assess short-term memory, namely the object recognition task, inhibitory avoidance and modified Y-maze.

KEY RESULTS

Scopolamine (1.0 mg·kg(-1) , i.p.) impaired short-term memory performance in all three tests and this scopolamine-induced amnesia was prevented by the A2 A receptor antagonist (SCH 58261, 0.1-1.0 mg·kg(-1) , i.p.) and by the A1 receptor antagonist (DPCPX, 0.2-5.0 mg·kg(-1) , i.p.), except in the modified Y-maze where only SCH58261 was effective. Both antagonists were devoid of effects on memory or locomotion in naïve rats. Notably, the activation of A2 A receptors with CGS 21680 (0.1-0.5 mg·kg(-1) , i.p.) before the training session was sufficient to trigger memory impairment in the three tests in naïve mice, and this effect was prevented by SCH 58261 (1.0 mg·kg(-1) , i.p.). Furthermore, i.c.v. administration of CGS 21680 (50 nmol) also impaired recognition memory in the object recognition task.

CONCLUSIONS AND IMPLICATIONS

These results show that A2 A receptors are necessary and sufficient to trigger memory impairment and further suggest that A1 receptors might also be selectively engaged to control the cholinergic-driven memory impairment.

Ketamine reduces neuronal degeneration and anxiety levels when administered during early life-induced status epilepticus in rats

Status epilepticus (SE) when occurred during brain development can cause short- and long-term consequences, which are frequently associated with NMDA-mediated glutamatergic excitotoxicity. In the present work, we investigated the putative neuroprotective role of ketamine, an NMDA receptor antagonist, on early life SE-induced acute neuronal death and long-term behavioral abnormalities. Male Wistar rats (16 postnatal days) were induced to SE by LiCl-pilocarpine i.p. administration (3 mEq/kg; 60 mg/kg, respectively). Fifteen or 60min after pilocarpine injection, animals received a ketamine administration (22.5mg/kg i.p.). Neuronal degeneration was assessed 24h after SE induction. Another subset of animals was destined to behavioral tasks in adulthood (75-80 postnatal days). Fluoro-Jade C labeling revealed a marked neuronal death on CA1 hippocampal subfield, habenula, thalamus and amygdala in SE animals. Ketamine post-SE onset treatment prevented neuronal death in all regions assessed. In the elevated plus maze, SE induced an increase in anxiety-like behaviors whereas ketamine administration during seizures was able to prevent this alteration. Ketamine administration in non-SE animals resulted in high anxiety levels. There were no observed differences among groups in the open field task in all parameters analyzed. Our results suggest that ketamine post-SE onset treatment was effective in preventing acute and long-standing alterations caused by SE early in life, which indicates a putative role of glutamatergic system on SE-induced brain damage as well as long-lasting behavioral consequences.