Adolescent Alcohol Exposure Reduces Behavioral Flexibility, Promotes Disinhibition and Increases Resistance to Extinction of Ethanol Self-Administration in Adulthood

The prefrontal cortex (PFC) is a brain region that is critically involved in cognitive function and inhibitory control of behavior, and adolescence represents an important period of continued PFC development that parallels the maturation of these functions. Evidence suggests that this period of continued development of the PFC may render it especially vulnerable to environmental insults that impact PFC function in adulthood. Experimentation with alcohol typically begins during adolescence when binge-like consumption of large quantities is common. In the present study, we investigated the effects of repeated cycles of adolescent intermittent ethanol (AIE) exposure (postnatal days 28–42) by vapor inhalation on different aspects of executive functioning in the adult rat. In an operant set-shifting task, AIE-exposed rats exhibited deficits in their ability to shift their response strategy when the rules of the task changed, indicating reduced behavioral flexibility. There were no differences in progressive ratio response for the reinforcer suggesting that AIE did not alter reinforcer motivation. Examination of performance on the elevated plus maze under conditions designed to minimize stress revealed that AIE exposure enhanced the number of entries into the open arms, which may reflect either reduced anxiety and/or disinhibition of exploratory-like behavior. In rats that trained to self-administer ethanol in an operant paradigm, AIE increased resistance to extinction of ethanol-seeking behavior. This resistance to extinction was reversed by positive allosteric modulation of mGluR5 during extinction training, an effect that is thought to reflect promotion of extinction learning mechanisms within the medial PFC. Consistent with this, CDPPB was also observed to reverse the deficits in behavioral flexibility. Finally, diffusion tensor imaging with multivariate analysis of 32 brain areas revealed that while there were no differences in the total brain volume, the volume of a subgroup of regions (hippocampus, thalamus, dorsal striatum, neocortex, and hypothalamus) were significantly different in AIE-exposed adults compared with litter-matched Control rats. Taken together, these findings demonstrate that binge-like exposure to alcohol during early to middle adolescence results in deficits in PFC-mediated behavioral control in adulthood

Binge-Like Alcohol Exposure During Adolescence Disrupts Dopaminergic Neurotransmission in the Adult Prelimbic Cortex

Repeated binge-like exposure to alcohol during adolescence has been reported to perturb prefrontal cortical development, yet the mechanisms underlying these effects are unknown. Here we report that adolescent intermittent ethanol exposure induces cellular and dopaminergic abnormalities in the adult prelimbic cortex (PrL-C). Exposing rats to alcohol during early-mid adolescence (PD28–42) increased the density of long/thin dendritic spines of layer 5 pyramidal neurons in the adult PrL-C. Interestingly, although AIE exposure did not alter the expression of glutamatergic proteins in the adult PrL-C, there was a pronounced reduction in dopamine (DA) D1 receptor modulation of both intrinsic firing and evoked NMDA currents in pyramidal cells, whereas D2 receptor function was unaltered. Recordings from fast-spiking interneurons also revealed that AIE reduced intrinsic excitability, glutamatergic signaling, and D1 receptor modulation of these cells. Analysis of PrL-C tissue of AIE-exposed rats further revealed persistent changes in the expression of DA-related proteins, including reductions in the expression of tyrosine hydroxylase and catechol-O-methyltransferase (COMT). AIE exposure was associated with hypermethylation of the COMT promoter at a conserved CpG site in exon II. Taken together, these findings demonstrate that AIE exposure disrupts DA and GABAergic transmission in the adult medial prefrontal cortex (mPFC). As DA and GABA work in concert to shape and synchronize neuronal ensembles in the PFC, these alterations could contribute to deficits in behavioral control and decision-making in adults who abused alcohol during adolescence

Chronic Alcohol Exposure Alters Behavioral and Synaptic Plasticity of the Rodent Prefrontal Cortex

In the present study, we used a mouse model of chronic intermittent ethanol (CIE) exposure to examine how CIE alters the plasticity of the medial prefrontal cortex (mPFC). In acute slices obtained either immediately or 1-week after the last episode of alcohol exposure, voltage-clamp recording of excitatory post-synaptic currents (EPSCs) in mPFC layer V pyramidal neurons revealed that CIE exposure resulted in an increase in the NMDA/AMPA current ratio. This increase appeared to result from a selective increase in the NMDA component of the EPSC. Consistent with this, Western blot analysis of the postsynaptic density fraction showed that while there was no change in expression of the AMPA GluR1 subunit, NMDA NR1 and NRB subunits were significantly increased in CIE exposed mice when examined immediately after the last episode of alcohol exposure. Unexpectedly, this increase in NR1 and NR2B was no longer observed after 1-week of withdrawal in spite of a persistent increase in synaptic NMDA currents. Analysis of spines on the basal dendrites of layer V neurons revealed that while the total density of spines was not altered, there was a selective increase in the density of mushroom-type spines following CIE exposure. Examination of NMDA-receptor mediated spike-timing-dependent plasticity (STDP) showed that CIE exposure was associated with altered expression of long-term potentiation (LTP). Lastly, behavioral studies using an attentional set-shifting task that depends upon the mPFC for optimal performance revealed deficits in cognitive flexibility in CIE exposed mice when tested up to 1-week after the last episode of alcohol exposure. Taken together, these observations are consistent with those in human alcoholics showing protracted deficits in executive function, and suggest these deficits may be associated with alterations in synaptic plasticity in the mPFC

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Adolescent Alcohol Exposure Results in Sex-specific Alterations in Conditioned Fear Learning and Memory in Adulthood

The present study used auditory fear conditioning to assess the impact of repeated binge-like episodes of alcohol exposure during adolescence on conditioned fear in adulthood. Male and female Long-Evans rats were subjected to adolescent intermittent ethanol (AIE) exposure by vapor inhalation between post-natal day 28 and 44. After aging into adulthood, rats then underwent fear conditioning by exposure to a series of tone-shock pairings. This was followed by cued-tone extinction training, and then testing of fear recovery. In male rats, AIE exposure enhanced conditioned freezing but did not alter the time-course of extinction of cued-tone freezing. During subsequent assessment of fear recovery, AIE exposed rats exhibited less freezing during contextual fear renewal, but greater freezing during extinction recall and spontaneous recovery. Compared to males, female rats exhibited significantly lower levels of freezing during fear conditioning, more rapid extinction of freezing behavior, and significantly lower levels of freezing during the tests of fear recovery. Unlike males that were all classified as high conditioners; female rats could be parsed into either a high or low conditioning group. However, irrespective of their level of conditioned freezing, both the high and low conditioning groups of female rats exhibited rapid extinction of conditioned freezing behavior and comparatively low levels of freezing in tests of fear recovery. Regardless of group classification, AIE had no effect on freezing behavior in female rats during acquisition, extinction, or fear recovery. Lastly, exposure of male rats to the mGlu5 positive allosteric modulator CDPPB prevented AIE-induced alterations in freezing. Taken together, these observations demonstrate sex-specific changes in conditioned fear behaviors that are reversible by pharmacological interventions that target mGlu5 receptor activation

Ontogenetic Quinpirole Treatments Produce Spatial Memory Deficits and Enhance Skilled Reaching in Adult Rats

There is a paucity of data on neurochemical abnormalities and associated effects on cognition and motor performance in rats ontogenetically treated with quinpirole, a rodent model of dopaminergic hyperfunction. The objective of the current study was to analyze the cognitive and motor effects produced by ontogenetic administration of quinpirole, a dopamine D2/D3 receptor agonist. Past research from this laboratory has shown that ontogenetic quinpirole treatment sensitizes D2 receptors and produces a variety of characteristic stereotypic behaviors in adult rats. In the current study, rats received quinpirole HCl (1 mg/kg/day) or saline from postnatal day (PD) 1 to PD 11 and went otherwise untreated until adulthood (PD 60). In Experiment 1, cognitive performance was assessed on the standard and matching-to-place versions of the Morris water task (MWT). In Experiment 2, skilled motor performance was assessed on the Whishaw reaching task and locomotor activity was also analyzed. We found that ontogenetically quinpirole-treated rats displayed a deficit on the probe trial given at the end of training of the standard version of the MWT but that there were no significant differences from control on the matching-to-place task. Additionally, rats treated in ontogeny with quinpirole showed significant enhancement in reaching accuracy on the Whishaw reaching task as well as increased locomotor activity relative to saline controls. These findings demonstrate that ontogenetic quinpirole treatments produce cognitive deficits, enhanced skilled reaching and hyperlocomotion. The behavioral changes produced by ontogenetic quinpirole treatment are consistent with dopaminergic hyperfunction, and possible mechanisms are discussed

Behavioral and Neuroinflammatory Sex Differences in Comorbid Posttraumatic Stress Disorder and Alcohol Use Disorder

Post-traumatic stress disorder (PTSD) is a debilitating disorder with a prevalence rate of approximately 5%. Unfortunately, this disorder is commonly associated with another debilitating disorder, alcohol use disorder (AUD). Of the 5% of people diagnosed with PTSD, 30%-59% also suffer from AUD. Currently, there are limited effective treatment options for those suffering from comorbid PTSD/AUD. Previous research has suggested that biological sex differentially impacts PTSD comorbid with AUD, however, the underlying mechanisms are enigmatic. The goal of this study was to better understand the underlying mechanisms that mediate sex differences in a rodent model of comorbid PTSD/AUD by analyzing specific behavioral tasks and changes in neuronal function of specific brain regions. Chronic inflammation has been implicated in PTSD and AUD respectively, with differences between sexes being observed. Females tend to express elevated levels of inflammation in both disorders compared to males in brain regions such as, the hippocampus, amygdala, and prefrontal cortex. Tumor necrosis factor α (TNF-α) is a proinflammatory cytokine that is released during neuronal inflammation. To further examine these sex differences, a comorbid PTSD/AUD rodent model was implemented using restraint stress (RS) and chronic intermittent ethanol use (CIE). Following the exposure to RS and CIE a fear conditioning procedure was implemented to assess changes in future stress sensitivity. The fear conditioning paradigm was accomplished by conditioning the animal to pair a tone with a foot shock, followed by extinction of that behavior in a different context where the animal received the tone but no foot shock. Thereafter, the animal was placed back in the context they received the foot shock, known as context renewal, but acquired no tone or foot shock. The behavior in these different contexts was analyzed to test memory and stress sensitivity. Brain tissue was collected to analyze TNF-α protein expression in regions associated with learning, memory, and addiction such as, the prelimbic cortex (PrL), infralimbic cortex (IfL), and the hippocampus. The results of the fear conditioning revealed that the females froze more altogether compared to the males, and there was more freezing of the females with RS and CIE during context renewal. It is expected that TNF-α protein expression will be significantly elevated in females when compared to males, regardless of treatment group. Females exposed to RS and CIE will have significantly higher TNF-α levels when compared to all other treatment groups. Finally, increases in TNF-α protein expression will be region specific with the PrL and IfL regions exhibiting significantly greater expression than the hippocampus. This study will aid in better understanding the sex differences and lead to better treatment options that are sex-dependent for those diagnosed with comorbid PTSD/AUD

CDPPB attenuates risky behavior in a rodent model of PTSD/AUD comorbidity

Alcohol use disorder (AUD) is the leading cause of substance use disorders among Veterans and 55 to 75% of the population that are diagnosed with PTSD also receive a comorbid diagnosis of AUD. The co-diagnosis of PTSD/AUD is associated with neurocognitive changes such as increased impulsivity and risk-taking behavior, especially among individuals with combat-related trauma. Furthermore, increased neuroinflammation in subregions of the prefrontal cortex (PFC) are suggested to contribute to these neurocognitive changes. To better understand the cognitive deficits associated with co-occurring PTSD/AUD we incorporated a probabilistic discounting task (PDT) to model risk-based decision-making in male and female Wistar rats that were exposed to restraint stress (RS) and chronic intermittent ethanol exposure (CIE). Following RS and CIE, rats underwent lever press training through a series of different training phases, in which one lever delivered a small reward 100% of the time, and the other a large reward, delivered with descending probability each trial block. Pressing the large-reward lever during the final two trial blocks when it is disadvantageous to do so is considered “risky” behavior. A week prior to PDT, rats were treated prophylactically with CDPPB, a positive allosteric modulator of the metabotropic glutamate type 5 (mGlu5) receptor, to determine if the cognitive deficits caused by stress and alcohol exposure could be prevented. Additionally, to determine if our model mimicked the neuroinflammatory mechanism seen in the human condition and the therapeutic effects of CDPPB, we assessed TNF-⍺ protein expression in a subset of rats. Our results indicated that male rats exposed to RS and CIE had significantly greater responding during the 3rd, 4th, and 5th risk blocks compared to all other groups. However, the administration of CDPPB reversed this effect. Females exposed to RS and CIE only displayed increased risky behavior at the highest risk block and this was also blocked with the administration of CDPPB. We also determined that RS and CIE significantly increased TNF-⍺ levels in the IfL cortex compared to either RS or CIE alone and the prophylactic administration of CDPPB reduced TNF-⍺ protein expression to control animal levels. In the present study, we demonstrate that exposure to stress and chronic alcohol leads to significant neurocognitive deficits resulting in increased risky decision-making, but these deficits can be attenuated through modulation of the mGlu5 receptor prior to behavioral testing. Additionally, these deficits could be due to deleterious neuroinflammation in subregions of the PFC

Modulation of mGlu5 Improves Sensorimotor Gating Deficits in Rats Neonatally Treated With Quinpirole Through Changes in Dopamine D2 Signaling

This study analyzed whether the positive allosteric modulator of metabotropic glutamate receptor type 5 (mGlu5) 3-Cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl) benzamide (CDPPB) would alleviate deficits in prepulse inhibition (PPI) and affect dopamine (DA) D2 signaling in the dorsal striatum and prefrontal cortex (PFC) in the neonatal quinpirole (NQ) model of schizophrenia (SZ). Male and female Sprague-Dawley rats were neonatally treated with either saline (NS) or quinpirole HCL (1 mg/kg; NQ), a DAD2 receptor agonist, from postnatal days (P) 1–21. Rats were raised to P44 and behaviorally tested on PPI from P44-P48. Before each trial, rats were subcutaneous (sc) administered saline or CDPPB (10 mg/kg or 30 mg/kg). On P50, rats were given a spontaneous locomotor activity test after CDPPB or saline administration. On P51, the dorsal striatum and PFC were evaluated for both arrestin-2 (βA-2) and phospho-AKT protein levels. NQ-treated rats demonstrated a significant deficit in PPI, which was alleviated to control levels by the 30 mg/kg dose of CDPPB. There were no significant effects of CDPPB on locomotor activity. NQ treatment increased βA-2 and decreased phospho-AKT in both the dorsal striatum and PFC, consistent with an increase DAD2 signaling. The 30 mg/kg dose of CDPPB significantly reversed changes in βA-2 in the dorsal striatum and PFC and phospho-AKT in the PFC equivalent to controls. Both doses of CDPPB produced a decrease of phospho-AKT in the PFC compared to controls. This study revealed that a mGlu5 positive allosteric modulator was effective to alleviate PPI deficits and striatal DAD2 signaling in the NQ model of SZ