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Due to the recent legalization ofCannabisin many jurisdictions and the consistent trend of increasing THC content inCannabisproducts, there is an urgent need to understand the impact ofCannabisuse during pregnancy on fetal neurodevelopment and behavior. To this end, we repeatedly exposed female Sprague-Dawley rats toCannabissmoke from gestational days 6 to 20 (n=12; Aphria Mohawk; 19.51% THC, Cannabissmoke. A significant increase in the male-to-female ratio was noted in theCannabis-exposed litters. In adulthood, both male and femaleCannabissmoke-exposed offspring explored the inner zone of an open field significantly less than control offspring. GestationalCannabissmoke exposure did not affect behavior on the elevated plus maze test or social interaction test in the offspring.Cannabisoffspring 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 RNAseq 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-THCCannabissmoke during gestation alters maternal physiological parameters, sex ratio, and anxiety-like behaviors in the adulthood offspring.Significance statementCannabisuse by pregnant women has increased alongside increased THC content in recent years. As smokingCannabisis the most common method of use, we used a validated model ofCannabissmoke exposure to repeatedly expose pregnant rats to combusted high-THCCannabissmoke. Our results show alterations in litter sex ratio, anxiety-like behavior, and decision making in the offspring which may relate to subtle changes in expression of amygdala genes related to development, cellular function, and nervous system disease. Thus, we believe this gestationalCannabisexposure model may be useful in delineating long-term effects on the offspring.

There is significant interest in the use of cannabinoids for the treatment of many epilepsies including absence epilepsy (AE). Genetic Absence Epilepsy Rats from Strasbourg (GAERS) model many aspects of AE including the presence of spike-and-wave discharges (SWDs) on electroencephalogram (EEG) and behavioral comorbidities, such as elevated anxiety. However, the effects of cannabis plant-based phytocannabinoids have not been tested in GAERS. Therefore, we investigated how SWDs in GAERS are altered by the two most common phytocannabinoids, Δ9 -tetrahydrocannabinol (THC) and cannabidiol (CBD), and exposure to smoke from two different chemovars of cannabis. Animals were implanted with bipolar electrodes in the somatosensory cortex and EEGs were recorded for 2 hr. Injected THC (1-10 mg/kg, i.p.) dose-dependently increased SWDs to over 200% of baseline. In contrast, CBD (30-100 mg/kg, i.p.) produced a ~50% reduction in SWDs. Exposure to smoke from a commercially available chemovar of high-THC cannabis (Mohawk, Aphria Inc.) increased SWDs whereas a low-THC/high-CBD chemovar of cannabis (Treasure Island, Aphria Inc.) did not significantly affect SWDs in GAERS. Pre-treatment with a CB1R antagonist (SR141716A) did not prevent the high-THC cannabis smoke from increasing SWDs, suggesting that the THC-mediated increase may not be CB1R-dependent. Plasma concentrations of THC and CBD were similar to previously reported values following injection and smoke exposure. Compared to injected CBD, it appears Treasure Island did not increase plasma levels sufficiently to observe an anti-epileptic effect. Together these experiments provide initial evidence that acute phytocannabinoid administration exerts the biphasic modulation of SWDs and may differentially impact patients with AE.

Antipsychotics help alleviate the positive symptoms associated with schizophrenia; however, their debilitating side effects have spurred the search for better treatment options. Novel compounds can be screened for antipsychotic potential in neuronal cell cultures and following acute N-methyl-D-aspartate (NMDA) receptor blockade with non-competitive antagonists such as MK-801 in rodent behavioral models. Given the known interactions between NMDA receptors and type 1 cannabinoid receptors (CB1R), compounds that modulate CB1Rs may have therapeutic potential for schizophrenia. This study assessed whether the CB1R positive allosteric modulator GAT211, when compared to ∆9-tetrahydrocannabinol (THC), has potential to reduce psychiatric behavioral phenotypes following acute MK-801 treatment in rats, and block hyperdopaminergic signalling associated with those behaviors. The effects of GAT211 and THC on cellular signaling were compared in Neuro2a cells, and behavioral effects of GAT211 and THC on altered locomotor activity and prepulse inhibition of the acoustic startle response caused by acute MK-801 treatment were assessed in male, Long Evans rats. GAT211 limited dopamine D2 receptor-mediated extracellular regulated kinase (ERK) phosphorylation in Neuro2a cells, whereas THC did not. As expected, acute MK-801 (0.15 mg/kg) produced a significant increase in locomotor activity and impaired PPI. GAT211 treatment alone (0.3–3.0 mg/kg) dose-dependently reduced locomotor activity and the acoustic startle response. GAT211 (3.0 mg/kg) also prevented hyperlocomotion caused by MK-801 but did not significantly affect PPI impairments. Taken together, these findings support continued preclinical research regarding the usefulness of CB1R positive allosteric modulators as antipsychotics.

Traumatic brain injuries (TBI) remain one of the leading causes of death and disability world-wide. One emerging area of TBI research is the involvement of the endocannabinoid system (ECS) in response to TBI. Endogenous cannabinoids modulate inflammation, pain, anxiety, and neurotransmitter release through the activation of the cannabinoid receptors CB1R and CB2R. CB1R and CB2R are activated by exogenous cannabinoids such as Δ9-tetrahydrocannabinol (THC) found in Cannabis sativa. As public perceptions change in the wake of Cannabis legalization, research into the potential harmful and therapeutic effects of THC following TBI deserve exploration. In this preliminary study, we investigated sex differences in behavioral effects, CB1R abundance, and cytokine profiles in a rat model of moderate TBI treated with 1 mg·kg-1 THC (i.p.). Neither TBI nor THC treatment altered catalepsy, body temperature, nociception, or spontaneous alternation as measured in the y-maze. TBI reduced male rotarod performance in both vehicle and THC-treated groups, and THC treatment decreased performance in Sham-TBI rats when compared to vehicle controls. Female rats that received a TBI and THC exhibited lower relative CB1R density when compared to the Sham-TBI+THC group. TBI was associated with reduced interleukin-4 in males; THC increased interleukin-6 in TBI males compared to Sham-TBI. These preliminary results highlight fundamental sex differences in the response of the ECS following TBI. Our results indicate the need for further investigation of the ECS and phytocannabinoids post-TBI in both acute and chronic phases.Significance StatementThe endogenous cannabinoid system is a potential target in the pathophysiology and treatment of traumatic brain injury (TBI). In this study we observed TBI reduced rotarod performance in male rats only and performance was not affected by THC. Female rats the received THC and TBI displayed lower cortical cannabinoid receptor 1 levels. These early results showcase sex differences in rodent models of TBI and the endogenous cannabinoid system.

Executive functions including working memory (WM) and attention are altered following Cannabis exposure in humans. To test for similar effects in a rodent model, we exposed adult male rats to acute Cannabis smoke before testing them on touchscreen-based tasks that assess these executive processes. The trial-unique, delayed nonmatching-to-location (TUNL) task was used to evaluate WM, task performance at different spatial pattern separations, and response latencies. The five-choice serial reaction time task (5-CSRTT) was used to measure attention, impulsivity, perseveration, and response latencies. Rats were exposed acutely to high- Δ

The formation and retention of hippocampus-dependent memories is impacted by neurogenesis, a process that involves the production of new neurons in the dentate gyrus of the hippocampus. Recent studies demonstrate that increasing neurogenesis after memory formation induces forgetting of previously acquired memories. Neurogenesis-induced forgetting was originally demonstrated in mice, but a recent report suggests that the same effect may be absent in rats. Although a general species difference is possible, other potential explanations for these incongruent findings are that memories which are more strongly reinforced become resilient to forgetting or that perhaps only certain types of memories are affected. Here, we investigated whether neurogenesis-induced forgetting occurs in rats using several hippocampal dependent tasks including contextual fear conditioning (CFC), the Morris Water Task (MWT), and touchscreen paired associates learning (PAL). Neurogenesis was increased following training using voluntary exercise for 4 weeks before recall of the previous memory was assessed. We show that voluntary running causes forgetting of context fear memories in a neurogenesis-dependent manner, and that neurogenesis-induced forgetting is present in rats across behavioral tasks despite differences in complexity or reliance on spatial, context, or object memories. In addition, we asked whether stronger memories are less susceptible to forgetting by varying the strength of training. Even with a very strong training protocol in the CFC task, we still observed enhanced forgetting related to increased neurogenesis. These results suggest that forgetting due to neurogenesis is a conserved mechanism that aids in the clearance of memories.Significance StatementRecent evidence indicates that hippocampal neurogenesis mediates forgetting of older memories and enhances encoding of new memories free of proactive interference. This evidence comes from multiple rodent species, behavioral tasks, and methods of increasing neurogenesis. However, a recent paper by (Kodali et al. 2016) found that voluntary exercise-induced neurogenesis did not cause forgetting in the Morris Water Task in rats. The results call into question whether the phenomenon is a conserved function of neurogenesis across species. In the present study, we show that voluntary running causes robust forgetting in rats in a neurogenesis-dependent manner and that the effect is present across three different behavioral tasks, confirming the existence of the phenomenon in rats and adding to the growing evidence that forgetting is a conserved function of hippocampal neurogenesis.

Altered interactions between endocannabinoid and glutamate signaling may be involved in the pathophysiology of schizophrenia and acute psychosis. As cognitive disturbances are involved in schizophrenia, increased understanding of the roles of these neurotransmitter systems in cognition may lead to the development of novel therapeutics for disorder. In the present study, we examined the effects of a recently synthesized cannabinoid receptor 1 (CB1R) positive allosteric modulator GAT211 in a rodent model of acute psychosis induced by systemic treatment with MK-801. To assess cognitive function, we used the Five-Choice Serial Reaction Time (5CSRT) task, conducted in touchscreen-equipped operant conditioning chambers. Our measures of primary interest were accuracy – indicative of visual attentional capacity – and the number of premature responses – indicative of impulsivity. We also measured latencies, omissions, and perseverative responding during all test sessions. Thirteen adult male Long Evans rats were trained on the 5CSRT and were then tested using a repeated measures design with acute MK-801 (0 or 0.15 mg/kg, i.p.) and GAT211 (0, 3, or 10 mg/kg, i.p.) administration. Acute MK-801 severely impaired accuracy, increased omissions, and increased the number of premature responses. MK-801 also significantly increased correct response latencies, without significant effects on incorrect or reward correction latencies. GAT211 had no significant effects when administered alone, or in combination with acute MK-801. These data confirm the dramatic effects of acute MK-801 treatment on behavioral measures of attention and impulsivity. Continued investigation of CB1R positive allosteric modulators as potential treatments for the cognitive symptoms of schizophrenia and related disorders should be pursued in other rodent models.

Antipsychotics help alleviate the positive symptoms associated with schizophrenia; however, their debilitating side effects have spurred the search for better treatment options. Novel compounds can be screened for antipsychotic potential in neuronal cell cultures and following acute N-methyl-D-aspartate (NMDA) receptor blockade with non-competitive antagonists such as MK-801 in rodent behavioral models. Given the known interactions between NMDA receptors and type 1 cannabinoid receptors (CB1R), compounds that modulate CB1Rs may have therapeutic potential for schizophrenia.This study assessed whether the CB1R positive allosteric modulator GAT211, when compared to ∆The effects of GAT211 and THC on cellular signaling were compared in Neuro2a cells, and behavioral effects of GAT211 and THC on altered locomotor activity and prepulse inhibition of the acoustic startle response caused by acute MK-801 treatment were assessed in male, Long Evans rats.GAT211 limited dopamine D2 receptor-mediated extracellular regulated kinase (ERK) phosphorylation in Neuro2a cells, whereas THC did not. As expected, acute MK-801 (0.15 mg/kg) produced a significant increase in locomotor activity and impaired PPI. GAT211 treatment alone (0.3-3.0 mg/kg) dose-dependently reduced locomotor activity and the acoustic startle response. GAT211 (3.0 mg/kg) also prevented hyperlocomotion caused by MK-801 but did not significantly affect PPI impairments.Taken together, these findings support continued preclinical research regarding the usefulness of CB1R positive allosteric modulators as antipsychotics.

Acute stress influences learning and memory in humans and rodents, enhancing performance in some tasks while impairing it in others. Typically, subjects preferentially employ striatal-mediated stimulus-response strategies in spatial memory tasks following stress, making use of fewer hippocampal-based strategies which may be more cognitively demanding. Previous research demonstrated that the acquisition of rodent paired associates learning (PAL) relies primarily on the striatum, while task performance after extensive training is impaired by hippocampal disruption. Therefore, we sought to explore whether the acquisition of PAL, an operant conditioning task involving spatial stimuli, could be enhanced by acute stress. Male Long-Evans rats were trained to a predefined criterion in PAL and then subjected to either a single session of restraint stress (30 min) or injection of corticosterone (CORT; 3 mg/kg). Subsequent task performance was monitored for one week. We found that rats subjected to restraint stress, but not those rats injected with CORT, performed with higher accuracy and efficiency, when compared to untreated controls. These results suggest that while acute stress enhances the acquisition of PAL, CORT alone does not. This dissociation may be due to differences between these treatments and their ability to produce sufficient catecholamine release in the amygdala, a requirement for stress effects on memory.

Research in asymmetrical visuospatial attention has identified a leftward bias in the general population across a variety of measures including visual attention and line-bisection tasks. In addition, increases in rightward collisions, or bumping, during visuospatial navigation tasks have been demonstrated in real world and virtual environments. However, little research has investigated these biases beyond the laboratory. The present study uses a semi-naturalistic approach and the online video game streaming service Twitch to examine navigational errors and assaults as skilled action video game players (n = 60) compete in Counter Strike: Global Offensive. This study showed a significant rightward bias in both fatal assaults and navigational errors. Analysis using the in-game ranking system as a measure of skill failed to show a relationship between bias and skill. These results suggest that a leftward visuospatial bias may exist in skilled players during online video game play. However, the present study was unable to account for some factors such as environmental symmetry and player handedness. In conclusion, video game streaming is a promising method for behavioural research in the future, however further study is required before one can determine whether these results are an artefact of the method applied, or representative of a genuine rightward bias.

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.

Absence Epilepsy (AE) is associated with recurrent losses of awareness and synchronous bilateral spike-wave discharges (SWDs). While seizures do not generally continue into adulthood, cognitive and behavioral comorbidities persist. One preclinical model used to investigate AE is the Genetic Absence Epilepsy Rats from Strasbourg (GAERS) which consistently have bilateral SWDs and similar behavioral profiles. In this experiment, we characterized discrimination learning and behavioral flexibility in female and male GAERS (n = 7 per sex) and Non-Epileptic Controls (NEC; n = 8 per sex) in a touchscreen-based version of visual discrimination (VD) and reversal learning (RL). We found that, on average, female GAERS required more sessions (12.3) to complete pretraining compared to female and male NEC (8.2 and 7.3, respectively) and male GAERS (9.4). In contrast, there was a sex-specific impairment during VD with male GAERS requiring more sessions on average (12.3) than male and female NEC (both 7.5) and female GAERS (8.3). Additionally, male GAERS completed >30% more selection and correction trials during VD and made >30% more errors. Both female and male GAERS required more sessions on average (9.1 and 10.7, respectively) of RL compared to female and male NEC (6.4 and 6.0 sessions, respectively). Accordingly, GAERS performed ∼30% more selection trials and correction trials compared to NEC, although only male GAERS made significantly more errors (>40%). Deficits in VD and RL were not associated with differences in correct or incorrect response latency, or reward collection latency, suggesting impairments are not due to alterations in locomotor activity or motivation. Together, these data suggest that GAERS have impaired behavioral flexibility and identify some sex-dependent differences. Thus, GAERS may be suitable for assessing the potential benefit of antiepileptic drugs on comorbid behavioral and cognitive deficits.

Childhood Absence Epilepsy (CAE) accounts for approximately 10% of all pediatric epilepsies. Current treatments for CAE are ineffective in approximately 1/3 of patients and can be associated with severe side effects such as hepatotoxicity. Certain cannabinoids, such as cannabidiol (CBD), have shown promise in the treatment of pediatric epilepsies. However, CBD remains limited or prohibited in many jurisdictions, and has not been shown to have efficacy in CAE. Modulation of the type 1 cannabinoid receptor (CB1R) may provide more desirable pharmacological treatments. Genetic Absence Epilepsy Rats from Strasbourg (GAERS) model many aspects of CAE, including cortical spike and wave discharges (SWDs). We have recently demonstrated that Δ9-tetrahydrocannabinol (THC) increases SWDs in GAERS whereas CBD decreases these events. Here, we characterized aspects of the endocannabinoid system in brain areas relevant to seizures in GAERS and tested whether positive allosteric modulators (PAMs) of CB1R reduced SWDs. Both female and male GAERS had reduced (>50%) expression of CB1R and elevated levels of the endocannabinoid 2-AG in cortex compared to non-epileptic controls (NEC). We then administered the CB1R PAMs GAT211 and GAT229 to GAERS implanted with cortical electrodes. Systemic administration of GAT211 to male GAERS reduced SWDs by 40%. Systemic GAT229 administration reduced SWDs in female and male GAERS. Intracerebral infusion of GAT229 into the cortex of male GAERS reduced SWDs by >60% in a CB1R-dependent manner that was blocked by SR141716A. Together, these experiments identify altered endocannabinoid tone in GAERS and suggest that CB1R PAMs should be explored for treatment of absence seizures.

Influenza during pregnancy is associated with the development of psychopathology in the offspring. We sought to determine whether maternal cytokines produced following administration of viral mimetic polyinosinic-polycytidylic acid (polyI:C) to pregnant rats were predictive of behavioral abnormalities in the adult offspring. Timed-pregnant Sprague Dawley rats received a single intravenous injection of 4-mg/kg polyI:C or saline on gestational day (GD)15. Blood was collected 3 h later for serum analysis of cytokine levels with ELISA. Male offspring were tested in a battery of behavioral tests during adulthood and behavior was correlated with maternal cytokine levels. Maternal serum levels of CXCL1 and interleukin (IL)-6, but not tumor necrosis factor (TNF)-α or CXCL2, were elevated in polyI:C-treated dams. PolyI:C-treated dams experienced post-treatment weight loss and polyI:C pups were smaller than controls at postnatal day (PND)1. Various behavior alterations were seen in the polyI:C-treated offspring. Male polyI:C offspring had enhanced MK-801-induced locomotion, and reduced sociability. PolyI:C offspring failed to display crossmodal and visual memory, and oddity preference was also impaired. Set-shifting, assessed with a lever-based operant conditioning task, was facilitated while touchscreen-based reversal learning was impaired. Correlations were found between maternal serum concentrations of CXCL1, acute maternal temperature and body weight changes, neonatal pup mass, and odd object discrimination and social behavior. Overall, while the offspring of polyI:C-treated rats displayed behavior abnormalities, maternal serum cytokines were not related to the long-term behavior changes in the offspring. Maternal sickness effects and neonatal pup size may be better indicators of later effects of maternal inflammation in the offspring.

Currently available antipsychotics are unsatisfactory given their side effects and limited efficacy for the cognitive symptoms of schizophrenia. Many currently available drugs, such as haloperidol, are T-type calcium channel antagonists in addition to their well-established antagonism of dopamine D2 receptors. Thus, preclinical research into the effects of T-type calcium channel antagonists/blockers in behavioral assays related to schizophrenia may inform novel therapeutic strategies. We explored the effects of a recently developed highly selective T-type calcium channel antagonist, Z944 (2.5, 5.0, 10.0 mg/kg), on the MK-801 (0.15 mg/kg) model of acute psychosis. To examine the effects of Z944 on behaviors relevant to schizophrenia, we tested touchscreen-based paired associates learning given its relevance to the cognitive symptoms of the disorder and locomotor activity given its relevance to the positive symptoms. Acute treatment with Z944 failed to reverse the visuospatial associative memory impairments caused by MK-801 in paired associates learning. The highest dose of drug (10.0 mg/kg) given alone produced subtle impairments on paired associates learning. In contrast, Z944 (5.0 mg/kg) blocked the expected increase in locomotion following MK-801 treatment in a locomotor assay. These experiments provide support that Z944 may reduce behaviors relevant to positive symptoms of schizophrenia, although additional study of its effects on cognition is required. These findings and other research suggest T-type calcium channel antagonists may be an alternative to currently available antipsychotics with less serious side effects.

Medial prefrontal cortex (mPFC) activity is fundamental for working memory (WM), attention, and behavioral inhibition; however, a comprehensive understanding of the neural computations underlying these processes is still forthcoming. Towards this goal, neural recordings were obtained from the mPFC of awake, behaving rats performing an odor span task of WM capacity. Neural populations were observed to encode distinct task epochs and the transitions between epochs were accompanied by abrupt shifts in neural activity patterns. Putative pyramidal neuron activity increased significantly earlier in the delay for sessions where rats achieved higher spans. Furthermore, increased putative interneuron activity was only observed at the termination of the delay thus indicating that local processing in inhibitory networks was a unique feature to initiate foraging. During foraging, changes in neural activity patterns associated with the approach to a novel odor, but not familiar odors, were robust. Collectively, these data suggest that distinct mPFC activity states underlie the delay, foraging, and reward epochs of the odor span task. Transitions between these states enable successful performance in dynamic environments placing strong demands on the substrates of working memory.