The T-type calcium channel antagonist, Z944, alters social behavior in Genetic Absence Epilepsy Rats from Strasbourg

Reticular Thalamic Hyperexcitability Drives Autism Spectrum Disorder Behaviors in the Cntnap2 Model of Autism

Autism spectrum disorders (ASDs) are a group of neurodevelopmental disorders characterized by social communication deficits, repetitive behaviors, and comorbidities such as sensory abnormalities, sleep disturbances, and seizures. Dysregulation of thalamocortical circuits has been implicated in these comorbid features, yet their precise roles in ASD pathophysiology remain elusive. This study focuses on the reticular thalamic nucleus (RT), a key regulator of thalamocortical interactions, to elucidate its contribution to ASD-related behavioral deficits using a Cntnap2 knockout (KO) mouse model. Our behavioral and EEG analyses comparing Cntnap2 +/+ and Cntnap2 -/- mice demonstrated that Cntnap2 knockout heightened seizure susceptibility, elevated locomotor activity, and produced hallmark ASD phenotypes, including social deficits, and repetitive behaviors. Electrophysiological recordings from thalamic brain slices revealed increased spontaneous and evoked network oscillations with increased RT excitability due to enhanced T-type calcium currents and burst firing. We observed behavior related heightened RT population activity in vivo with fiber photometry. Notably, suppressing RT activity via Z944, a T-type calcium channel blocker, and via C21 and the inhibitory DREADD hM4Di, improved ASD-related behavioral deficits. These findings identify RT hyperexcitability as a mechanistic driver of ASD behaviors and underscore RT as a potential therapeutic target for modulating thalamocortical circuit dysfunction in ASD.

Teaser

RT hyperexcitability drives ASD behaviors in Cntnap2-/- mice, highlighting RT as a therapeutic target for circuit dysfunction.

Differential effects of gestational Cannabis smoke and phytocannabinoid injections on male and female rat offspring behavior

Our understanding of the implications of gestational Cannabis exposure (GCE) remains unclear as Cannabis use increases worldwide. Much of the existing knowledge of the effects of GCE has been gained from preclinical experiments using injections of isolated Δ9-tetrahydrocannabinol (THC) at relatively high doses. Few investigations of the effects of GCE to smoke from the whole Cannabis flower have been conducted, despite this being the most common mode of human consumption. Here, we compared the effects of repeated gestational exposure to high-THC or high-cannabidiol (CBD) Cannabis smoke to i.p. THC or i.p. CBD to those of GCE to high-THC or high-CBD Cannabis smoke on litter health and the offspring. We found that injecting phytocannabinoids generally had a more severe impact on measures of maternal and litter health and produced distinct behavioral phenotypes when compared to offspring from dams treated with high-THC and high-CBD smoke during gestation. GCE to high-THC smoke decreased prepulse inhibition (PPI) and MK-801-induced locomotor activity in female adolescent offspring, which normalized in adulthood. GCE to i.p. THC increased exploratory behavior in the open field test in adolescent offspring of both sexes. GCE had a negative impact on offspring performance in the Identical Stimuli Test and Different Stimuli Test with odors regardless of gestational treatment, sex, or age. CBD (i.p) impaired PPI in both male and female offspring in adulthood and increased time spent in proximity during social interaction for male offspring. There were no effects of GCE in the 5 Choice Serial Reaction Time Task. These data establish distinct behavioral phenotypes in the offspring between smoked and injected GCE, further demonstrating that route and specific phytocannabinoid dose produce differential outcomes across offspring lifespan. Smoked Cannabis is still the most common means of consumption, and more preclinical investigation is needed to determine the effects of smoked Cannabis on developmental trajectories.

A quantitative and T-pattern analysis of anxiety-like behavior in male GAERS, NEC, and Wistar rats bred under the same conditions, against a commercially available Wistar control group in the hole board and elevated plus maze tests

AIM

The Genetic Absence Epilepsy Rats from Strasbourg (GAERS) are an inbred polygenic model of childhood absence epilepsy (CAE), which, as their non-epileptic control (NEC) rats, are derived from Wistar rats. While the validity of GAERS in reproducing absence seizures is well established, its use as a model for CAE psychiatric comorbidities has been subject to conflicting findings. Differences in colonies, experimental procedures, and the use of diverse controls from different breeders may account for these disparities. Therefore, in this study, we compared GAERS, NEC, and Wistar bred in the same animal facility with commercially available Wistar (Cm Wistar) as a third control.

METHODS

We performed hole board (HB) and elevated plus maze (EPM) tests that were analyzed with standard quantitative and T-pattern analysis in male, age-matched Cm Wistar and GAERS, NEC, and Wistar, bred under the same conditions, to rule out the influence of different housing factors and provide extra information on the structure of anxiety-like behavior of GAERS rats.

RESULTS

Quantitative analysis showed that GAERS and NEC had similar low anxiety-like behavior when compared to Cm Wistar but not to Wistar rats, although a higher hole-focused exploration was revealed in NEC. T-pattern analysis showed that GAERS, NEC, and Wistar had a similar anxiety status, whereas GAERS and NEC exhibited major differences with Cm Wistar but not Wistar rats. EPM results indicated that GAERS and NEC also have similar low anxiety compared to Cm Wistar and/or Wistar rats. Nevertheless, the analysis of the T-pattern containing open-arm entry showed GAERS and Wistar to be less anxious than NEC and Cm Wistar rats.

CONCLUSION

To summarize, comorbid anxiety may not be present in male GAERS rats. This study also highlighted the importance of including a control Wistar group bred under the same conditions when evaluating their behavior, as using Wistar rats from commercial breeders can lead to misleading results.

Repeated Exposure to High-THC Cannabis Smoke during Gestation Alters Sex Ratio, Behavior, and Amygdala Gene Expression of Sprague Dawley Rat Offspring

Because of the legalization of Cannabis in many jurisdictions and the trend of increasing Δ9-tetrahydrocannabinol (THC) content in Cannabis products, an urgent need exists to understand the impact of Cannabis use during pregnancy on fetal neurodevelopment and behavior. To this end, we exposed female Sprague Dawley rats to Cannabis smoke daily from gestational day 6 to 20 or room air. Maternal reproductive parameters, offspring behavior, and gene expression in the offspring amygdala were assessed. Body temperature was decreased in dams following smoke exposure and more fecal boli were observed in the chambers before and after smoke exposure in dams exposed to smoke. Maternal weight gain, food intake, gestational length, litter number, and litter weight were not altered by exposure to Cannabis smoke. A significant increase in the male-to-female ratio was noted in the Cannabis-exposed litters. In adulthood, male and female Cannabis smoke-exposed offspring explored the inner zone of an open field significantly less than control offspring. Gestational Cannabis smoke exposure did not affect behavior on the elevated plus maze test or social interaction test in the offspring. Cannabis offspring were better at visual pairwise discrimination and reversal learning tasks conducted in touchscreen-equipped operant conditioning chambers. Analysis of gene expression in the adult amygdala using RNA sequencing revealed subtle changes in genes related to development, cellular function, and nervous system disease in a subset of the male offspring. These results demonstrate that repeated exposure to high-THC Cannabis smoke during gestation alters maternal physiological parameters, sex ratio, and anxiety-like behaviors in the adulthood offspring.

Under or Absent Reporting of Light Stimuli in Testing of Anxiety-Like Behaviors in Rodents: The Need for Standardization

Behavioral neuroscience tests such as the Light/Dark Test, the Open Field Test, the Elevated Plus Maze Test, and the Three Chamber Social Interaction Test have become both essential and widely used behavioral tests for transgenic and pre-clinical models for drug screening and testing. However, as fast as the field has evolved and the contemporaneous involvement of technology, little assessment of the literature has been done to ensure that these behavioral neuroscience tests that are crucial to pre-clinical testing have well-controlled ethological motivation by the use of lighting (i.e., Lux). In the present review paper, N = 420 manuscripts were examined from 2015 to 2019 as a sample set (i.e., n = ~20–22 publications per year) and it was found that only a meager n = 50 publications (i.e., 11.9% of the publications sampled) met the criteria for proper anxiogenic and anxiolytic Lux reported. These findings illustrate a serious concern that behavioral neuroscience papers are not being vetted properly at the journal review level and are being released into the literature and public domain making it difficult to assess the quality of the science being reported. This creates a real need for standardizing the use of Lux in all publications on behavioral neuroscience techniques within the field to ensure that contributions are meaningful, avoid unnecessary duplication, and ultimately would serve to create a more efficient process within the pre-clinical screening/testing for drugs that serve as anxiolytic compounds that would prove more useful than what prior decades of work have produced. It is suggested that improving the standardization of the use and reporting of Lux in behavioral neuroscience tests and the standardization of peer-review processes overseeing the proper documentation of these methodological approaches in manuscripts could serve to advance pre-clinical testing for effective anxiolytic drugs. This report serves to highlight this concern and proposes strategies to proactively remedy them as the field moves forward for decades to come.

Cannabinoid 1/2 Receptor Activation Induces Strain-Dependent Behavioral and Neurochemical Changes in Genetic Absence Epilepsy Rats From Strasbourg and Non-epileptic Control Rats

Childhood absence epilepsy (CAE) is characterized by absence seizures, which are episodes of lack of consciousness accompanied by electrographic spike-wave discharges. About 60% of children and adolescents with absence seizures are affected by major neuropsychological comorbidities, including anxiety. Endocannabinoids and monoamines are likely involved in the pathophysiology of these CAE psychiatric comorbidities. Here, we show that the synthetic cannabinoid receptor type 1/2 (CB1/2R) agonist WIN 55,212-2 (2 mg/kg) has a strain-dependent effect on anxiety-like and motor behavior when assess in the hole board test and cerebral monoaminergic levels in Genetic Absence Epilepsy Rats from Strasbourg (GAERS) and their non-epileptic control (NEC) rat strain. Using quantitative and Temporal pattern (T-pattern) analyses, we found that WIN 55,212-2 did not affect the emotional status of GAERS, but it was anxiolytic in NEC. Conversely, WIN 55,212-2 had a sedative effect in GAERS but was ineffective in NEC. Moreover, vehicle-treated GAERS more motivated to explore by implementing more complex and articulated strategies. These behavioral changes correlate with the reduction of 5-HT in the hippocampus and substantia nigra (SN) and noradrenaline (NA) in the entopeduncular nucleus (EPN) in vehicle-treated GAERS compared to NEC rats, which could contribute to their low anxiety status and hypermotility, respectively. On the other hand, the increased level of NA in the EPN and 5-HT in the SN is consistent with an activation of the basal ganglia output-mediated motor suppression observed in WIN 55,212-2-treated GAERS rats. These data support the view of a strain-dependent alteration of the endocannabinoid system in absence epilepsy by adding evidence of a lower emotional responsiveness and a basal ganglia hypersensitivity to cannabinoids in GAERS compared to NEC rats.

Cerebellar contribution to absence epilepsy

The new aggregate data analyses revealed the earlier missing role of cerebellum long-term electrical stimulation in the absence epilepsy. Neurophysiologic data gained by authors favor that cerebellar serial deep brain stimulation (DBS) (100 Hz) causes the transformation of penicillin-induced cortical focal discharges into prolonged 3,5-3,75 sec oscillations resembling spike-wave discharges (SWD) in cats. Such SWDs were not organized in the form of bursts and persisted continuously after stimulation. Therefore, the appearance of prolonged periods of SWD is regarded as a tonic cerebellar influence upon pacemaker of SWD and might be caused by the long-lasting DBS-induced increase of GABA-ergic extrasynaptic inhibition in the forebrain networks. The absence seizure facilitation caused by cerebellar DBS was discussed with the reviewed data on optogenetic stimulation, neuronal activity of cerebellar structures, and imaging data.

The interictal activities load and cognitive performance of children with typical absence epilepsy

Background

The description of childhood absence epilepsy (CAE) a benign self-limited generalized epilepsy has become a matter of debate. The objectives of this work were to evaluate the existence of psychiatric and cognitive impairments among patients with typical CAE and to correlate their possible relation to seizure frequency, duration of epilepsy, IISL, and valproate therapy.

Methods

The study was conducted on 19 typical CAE patients receiving valproate therapy, 11 newly diagnosed CAE patients not receiving AEDs, and 30 healthy control subjects (HCS). Participants were subjected to medical history taking, EEG monitoring, child behavior checklist (CBCL), Stanford Binet Intelligence Scale 5th edition, and computerized psychometric tests that assess cognitive domains and executive functions.

Results

The study revealed a high rate of cognitive and psychiatric dysfunctions in CAE patients. 53.3% of patients had psychiatric problems versus 16.6% in HCS. Attention deficit hyperactive disorder (ADHD) (26.6%), anxiety (16.6%), and depression (6.6%) were the most common psychiatric disorders in the patient group. Withdrawn/depressed symptoms, thought problems, social problems, and attention problems in CAE patients were significantly increased compared to HCS. At the same time, CAE patients perform worse in cognitive scales than HCS with comparable intelligent quotient (IQ) scores.

Conclusion

Cognitive and psychiatric impairments in typical CAE patients appear multifactorial in origin with epilepsy-related factors including the duration of epilepsy and interictal spike load (IISL).

Absence seizures and their relationship to depression and anxiety: Evidence for bidirectionality

Absence seizures (AS), presenting as short losses of consciousness with staring spells, are a common manifestation of childhood epilepsy that is associated with behavioral, emotional, and social impairments. It has also been suggested that patients with AS are more likely to suffer from mood disorders such as depression and anxiety. This systematic review and meta-analysis synthesizes human and animal models that investigated mood disorders and AS. Of the 1019 scientific publications identified, 35 articles met the inclusion criteria for this review. We found that patients with AS had greater odds of developing depression and anxiety when compared to controls (odds ratio = 4.93, 95% confidence interval = 2.91-8.35, p < .01). The included studies further suggest a strong correlation between AS and depression and anxiety in the form of a bidirectional relationship. The current literature emphasizes that these conditions likely share underlying mechanisms, such as genetic predisposition, neurophysiology, and anatomical pathways. Further research will clarify this relationship and ensure more effective treatment for AS and mood disorders.

Atipamezole, a specific α2A 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 α_2A adrenergic receptors (α_2A ARs) in absence epilepsy is not well characterized. Therefore, we investigated the outcomes of the specific antagonism of α_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 α_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 μg/5 μL) 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 μg), 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 μg) 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 μg) compared to aCSF.

SIGNIFICANCE

This study emphasizes the α₂ AR-related modulation of absence epilepsy and particularly the significance of α₂ AR antagonism in suppressing SWDs. Atipamezole's SWD-suppressive actions may be through CaMKII-mediated second messenger systems in the thalamus.

T-type calcium channels regulate the acquisition and recall of conditioned fear in male, Wistar rats

The T-type calcium channel blocker, Z944, has been used as a pharmacological tool to assess T-type calcium channel function and examined for use as an anti-epileptic. As Z944 affects fear learning and memory in a rodent model of absence epilepsy, it is important to determine the effect of Z944 on learning and memory in a non-disease outbred rodent strain. This study examined the dose-dependent effects (5 mg/kg, 10 mg/kg, i.p.) of acute systemic treatment with Z944 on the learning and memory of fear conditioning and extinction in male Wistar rats. Z944 administered prior to the acquisition of fear conditioning significantly increased freezing prior to acquisition and extinction, during acquisition, and impaired recall of fear memory 24 h later. These findings suggest that T-type calcium channel activity may be required during associative learning for intact long-term memory. Enhanced fear behaviour observed prior to acquisition and extinction, and during acquisition could reflect an increase in anxiety, however, further testing is needed to determine the effect of Z944 on anxiety during fear conditioning and extinction. The use of Z944 for therapeutic purposes should consider the potential effects of Z944 on learning and memory in clinical populations.

Implementation of ezTrack open-source pipeline for quantifying rat locomotor behavior: Comparison to commercially available software

Animal tracking software is an important tool to record and analyze locomotor activity during behavioral assays that provides considerable advantages over traditional manual scoring approaches (e.g., counting line crosses on a grid overlay or using a stopwatch to score time spent in regions of interest). Although several options are available to researchers, tracking software is often costly or requires advanced technical knowledge to operate efficiently. In this study, a free open-source behavioral tracking pipeline called ezTrack was compared to commercially available software for assessing rat locomotor behavior and time spent in regions of interest during elevated plus maze (EPM) and open field test (OFT) assays. ezTrack produced nearly identical results to the commercial software. Overall, these results suggest that ezTrack is a cost-effective approach to quantify some aspects of behavior in these tasks.

Cognitive impairment in the WAG/Rij rat absence model is secondary to absence seizures and depressive-like behavior

Neuropsychiatric comorbidities are common in patients with epilepsy, remaining still an urgent unmet clinical need. Therefore, the management of epileptic disorders should not only be restricted to the achievement of seizure-freedom but must also be able to counteract its related comorbidities. Experimental animal models of epilepsy represent a valid tool not only to study epilepsy but also its associated comorbidities. The WAG/Rij rat is a well-established genetically-based model of absence epilepsy with depressive-like comorbidity, in which learning and memory impairment was also recently reported. Aim of this study was to clarify whether this cognitive decline is secondary or not to absence seizures and/or depressive-like behavior. The behavioral performance of untreated and ethosuximide-treated (300 mg/kg/day; 17 days) WAG/Rij rats at 6 and 12 months of age were assessed in several tests: forced swimming test, objects recognition test, social recognition test, Morris water maze and passive avoidance. According to our results, it seems that cognitive impairment in this strain, similarly to depressive-like behavior, is secondary to the occurrence of absence seizures, which might be necessary for the expression of cognitive impairment. Furthermore, our results suggest an age-dependent impairment of cognitive performance in WAG/Rij rats, which could be linked to the age-dependent increase of spike wave discharges. Consistently, it is possible that absence seizures, depressive-like behavior and cognitive deficit may arise independently and separately in lifetime from the same underlying network disease, as previously suggested for the behavioral features associated with other epileptic syndromes.