Hyper-Rigid Phasic Organization of Hippocampal Activity But Normal Spatial Properties of CA1 Place Cells in the Ts65Dn Mouse Model of Down Syndrome.

Down syndrome (DS) in humans is caused by trisomy of chromosome 21 and is marked by prominent difficulties in learning and memory. Decades of research have demonstrated that the hippocampus is a key structure in learning and memory, and recent work with mouse models of DS has suggested differences in hippocampal activity that may be the substrate of these differences. One of the primary functional differences in DS is thought to be an excess of GABAergic innervation from medial septum to the hippocampus. In these experiments, we probe in detail the activity of region CA1 of the hippocampus using in vivo electrophysiology in male Ts65Dn mice compared with their male nontrisomic 2N littermates. We find the spatial properties of place cells in CA1 are normal in Ts65Dn animals. However, we find that the phasic relationship of both CA1 place cells and gamma rhythms to theta rhythm in the hippocampus is profoundly altered in these mice. Since the phasic organization of place cell activity and gamma oscillations on the theta wave are thought to play a critical role in hippocampal function, the changes we observe agree with recent findings that organization of the hippocampal network is potentially of more relevance to its function than the spatial properties of place cells.SIGNIFICANCE STATEMENT Recent evidence has disrupted the view that spatial deficits are associated with place cell abnormalities. In these experiments, we record hippocampal place cells and local field potential from the Ts65Dn mouse model of Down syndrome, and find phenomenologically normal place cells, but profound changes in the association of place cells and gamma rhythms with theta rhythm, suggesting that the overall network state is critically important for hippocampal function. These findings also agree with evidence suggesting that excess inhibitory control is the cause of hippocampal dysfunction in Down syndrome. The findings also confirm new avenues for pharmacological treatment of Down syndrome.

Major disparities in patient-reported adherence compared to objective assessment of adherence using mass spectrometry: A prospective study in a tertiary-referral hypertension clinic.

AIM: Many challenges exist in determining true rates of adherence to antihypertensive medications among individuals in a clinic setting. For the first time, we aimed to compare patient-reported antihypertensive adherence with objective evidence using mass spectrometry spot urinalysis in a tertiary referral clinic setting. METHODS: A prospective observational single-centre cohort study was performed in a tertiary referral hypertension clinic, encompassing antihypertensive initiation and persistence. Patients were referred with apparent treatment-resistant hypertension or for suspected secondary causes. Participants completed a self-reported assessment of antihypertensive adherence and provided a spot urine sample. The presence of antihypertensive medications and/or their respective metabolites was evaluated using high-performance liquid chromatography tandem mass spectrometry. Patients were determined to be adherent if they demonstrated both self-reported adherence and objective mass spectrometry evidence. RESULTS: Of all 105 eligible participants initially recruited, 73 (69.5%) met the eligibility criteria. Only 27.4% (95% confidence interval 0.2-0.4) of participants demonstrated true adherence to their self-reported antihypertensives, despite 75.3% (0.6-0.8) reporting adherence. Greatest medication adherence was achieved with angiotensin II receptor blockers (61%), with calcium-channel blockers and mineralocorticoid antagonists demonstrating least adherence (38%). CONCLUSION: In patients attending a tertiary hypertension clinic, the combined use of spot urine mass spectrometry and self-reporting identifies higher rates of nonadherence when compared to either modality alone. Both techniques should be combined for more accurate detection of medication adherence.

Multi-dimensional relationships among dementia, depression and prescribed drugs in England and Wales hospitals.

BACKGROUND: Dementia is a group of symptoms that largely affects older people. The majority of patients face behavioural and psychological symptoms (BPSD) during the course of their illness. Alzheimer's disease (AD) and vascular dementia (VaD) are two of the most prevalent types of dementia. Available medications provide symptomatic benefits and provide relief from BPSD and associated health issues. However, it is unclear how specific dementia, antidepressant, antipsychotic, antianxiety, and mood stabiliser drugs, used in the treatment of depression and dementia subtypes are prescribed in hospital admission, during hospital stay, and at the time of discharge. To address this, we apply multi-dimensional data analytical approaches to understand drug prescribing practices within hospitals in England and Wales. METHODS: We made use of the UK National Audit of Dementia (NAD) dataset and pre-processed the dataset. We evaluated the pairwise Pearson correlation of the dataset and selected key data features which are highly correlated with dementia subtypes. After that, we selected drug prescribing behaviours (e.g. specific medications at the time of admission, during the hospital stay, and upon discharge), drugs and disorders. Then to shed light on the relations across multiple features or dimensions, we carried out multiple regression analyses, considering the number of dementia, antidepressant, antipsychotic, antianxiety, mood stabiliser, and antiepileptic/anticonvulsant drug prescriptions as dependent variables, and the prescription of other drugs, number of patients with dementia subtypes (AD/VaD), and depression as independent variables. RESULTS: In terms of antidepressant drugs prescribed in hospital admission, during stay and discharge, the number of sertraline and venlafaxine prescriptions were associated with the number of VaD patients whilst the number of mirtazapine prescriptions was associated with frontotemporal dementia patients. During admission, the number of lamotrigine prescriptions was associated with frontotemporal dementia patients, and with the number of valproate and dosulepin prescriptions. During discharge, the number of mirtazapine prescriptions was associated with the number of donepezil prescriptions in conjunction with frontotemporal dementia patients. Finally, the number of prescriptions of donepezil/memantine at admission, during hospital stay and at discharge exhibited positive association with AD patients. CONCLUSION: Our analyses reveal a complex, multifaceted set of interactions among prescribed drug types, dementia subtypes, and depression.

Effects of Intra-BLA Administration of PPAR Antagonists on Formalin-Evoked Nociceptive Behaviour, Fear-Conditioned Analgesia, and Conditioned Fear in the Presence or Absence of Nociceptive Tone in Rats.

There is evidence for the involvement of peroxisome proliferator-activated receptors (PPARs) in pain, cognition, and anxiety. However, their role in pain-fear interactions is unknown. The amygdala plays a key role in pain, conditioned fear, and fear-conditioned analgesia (FCA). We investigated the effects of intra-basolateral amygdala (BLA) administration of PPARα, PPARß/δ, and PPARγ antagonists on nociceptive behaviour, FCA, and conditioned fear in the presence or absence of nociceptive tone. Male Sprague-Dawley (SD) rats received footshock (FC) or no footshock (NFC) in a conditioning arena. Twenty-three and a half hours later, rats received an intraplantar injection of formalin or saline and, 15 min later, intra-BLA microinjections of vehicle, PPARα (GW6471) PPARß/δ (GSK0660), or PPARγ (GW9662) antagonists before arena re-exposure. Pain and fear-related behaviour were assessed, and neurotransmitters/endocannabinoids measured post-mortem. Intra-BLA administration of PPARα or PPARγ antagonists potentiated freezing in the presence of nociceptive tone. Blockade of all PPAR subtypes in the BLA increased freezing and BLA dopamine levels in NFC rats in the absence of nociceptive tone. Administration of intra-BLA PPARα and PPARγ antagonists increased levels of dopamine in the BLA compared with the vehicle-treated counterparts. In conclusion, PPARα and PPARγ in the BLA play a role in the expression or extinction of conditioned fear in the presence or absence of nociceptive tone.

In Vitro Model to Investigate Communication between Dorsal Root Ganglion and Spinal Cord Glia.

Chronic discogenic back pain is associated with increased inflammatory cytokine levels that can influence the proximal peripheral nervous system, namely the dorsal root ganglion (DRG). However, transition to chronic pain is widely thought to involve glial activation in the spinal cord. In this study, an in vitro model was used to evaluate the communication between DRG and spinal cord glia. Primary neonatal rat DRG cells were treated with/without inflammatory cytokines (TNF-α, IL-1ß, and IL-6). The conditioned media were collected at two time points (12 and 24 h) and applied to spinal cord mixed glial culture (MGC) for 24 h. Adult bovine DRG and spinal cord cell cultures were also tested, as an alternative large animal model, and results were compared with the neonatal rat findings. Compared with untreated DRG-conditioned medium, the second cytokine-treated DRG-conditioned medium (following medium change, thus containing solely DRG-derived molecules) elevated CD11b expression and calcium signal in neonatal rat microglia and enhanced Iba1 expression in adult bovine microglia. Cytokine treatment induced a DRG-mediated microgliosis. The described in vitro model allows the use of cells from large species and may represent an alternative to animal pain models (3R principles).

Increasing Endocannabinoid Tone Alters Anxiety-Like and Stress Coping Behaviour in Female Rats Prenatally Exposed to Valproic Acid.

Given the sex differences evident in the prevalence of autism, there is an increased awareness of the importance of including females in autism research to determine sexual dimorphism and sex-specific treatments. Cannabinoids and endocannabinoid modulators have been proposed as potential novel treatments for autism-related symptoms; however, few studies to date have examined if these pharmacological agents elicit sex-specific effects. The aim of the present study was to use the valproic acid (VPA) model of autism to compare the behavioural responses of male and female rats and examine the effects of increasing endocannabinoid tone on the behavioural responses of VPA-exposed female rats. These data revealed that VPA-exposed male, but not female, rats exhibit reduced social responding in the three-chamber and olfactory habituation/dishabituation (OHD) test during adolescence. In comparison, VPA-exposed female, but not male, adolescent rats exhibited anxiety-like behaviour in the elevated plus maze (EPM) and open field test (OFT). In VPA-exposed female rats, increasing 2-AG levels augmented anxiety-like behaviour in the EPM and OFT, while increasing AEA levels reduced stress coping behaviour in the swim stress test. These data highlight sexual dimorphic behaviours in the VPA model and indicate that enhancing endocannabinoid levels may exacerbate negative affective behaviour in VPA-exposed females. Thus, considerations should be paid to the possible sex-specific effects of cannabinoids for the treatment of symptoms associated with autism.

Shaping a data-driven era in dementia care pathway through computational neurology approaches.

BACKGROUND: Dementia is caused by a variety of neurodegenerative diseases and is associated with a decline in memory and other cognitive abilities, while inflicting an enormous socioeconomic burden. The complexity of dementia and its associated comorbidities presents immense challenges for dementia research and care, particularly in clinical decision-making. MAIN BODY: Despite the lack of disease-modifying therapies, there is an increasing and urgent need to make timely and accurate clinical decisions in dementia diagnosis and prognosis to allow appropriate care and treatment. However, the dementia care pathway is currently suboptimal. We propose that through computational approaches, understanding of dementia aetiology could be improved, and dementia assessments could be more standardised, objective and efficient. In particular, we suggest that these will involve appropriate data infrastructure, the use of data-driven computational neurology approaches and the development of practical clinical decision support systems. We also discuss the technical, structural, economic, political and policy-making challenges that accompany such implementations. CONCLUSION: The data-driven era for dementia research has arrived with the potential to transform the healthcare system, creating a more efficient, transparent and personalised service for dementia.

Pharmacological Blockade of PPAR Isoforms Increases Conditioned Fear Responding in the Presence of Nociceptive Tone.

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors with three isoforms (PPARα, PPARß/δ, PPARγ) and can regulate pain, anxiety, and cognition. However, their role in conditioned fear and pain-fear interactions has not yet been investigated. Here, we investigated the effects of systemically administered PPAR antagonists on formalin-evoked nociceptive behaviour, fear-conditioned analgesia (FCA), and conditioned fear in the presence of nociceptive tone in rats. Twenty-three and a half hours following fear conditioning to context, male Sprague-Dawley rats received an intraplantar injection of formalin and intraperitoneal administration of vehicle, PPARα (GW6471), PPARß/δ (GSK0660) or PPARγ (GW9662) antagonists, and 30 min later were re-exposed to the conditioning arena for 15 min. The PPAR antagonists did not alter nociceptive behaviour or fear-conditioned analgesia. The PPARα and PPARß/δ antagonists prolonged context-induced freezing in the presence of nociceptive tone without affecting its initial expression. The PPARγ antagonist potentiated freezing over the entire trial. In conclusion, pharmacological blockade of PPARα and PPARß/δ in the presence of formalin-evoked nociceptive tone, impaired short-term, within-trial fear-extinction in rats without affecting pain response, while blockade of PPARγ potentiated conditioned fear responding. These results suggest that endogenous signalling through these three PPAR isoforms may reduce the expression of conditioned fear in the presence of nociceptive tone.

Endocannabinoid modulation of inflammatory hyperalgesia in the IFN-α mouse model of depression.

Depression is a well-recognised effect of long-term treatment with interferon-alpha (IFN-α), a widely used treatment for chronic viral hepatitis and malignancy. In addition to the emotional disturbances, high incidences of painful symptoms such as headache and joint pain have also been reported following IFN-α treatment. The endocannabinoid system plays an important role in emotional and nociceptive processing, however it is unknown whether repeated IFN-α administration induces alterations in this system. The present study investigated nociceptive responding in the IFN-α-induced mouse model of depression and associated changes in the endocannabinoid system. Furthermore, the effects of modulating peripheral endocannabinoid tone on inflammatory pain-related behaviour in the IFN-α model was examined. Repeated IFN-α administration (8000 IU/g/day) to male C57/Bl6 mice increased immobility in the forced swim test and reduced sucrose preference, without altering body weight gain or locomotor activity, confirming development of the depressive-like phenotype. There was no effect of repeated IFN-α administration on latency to respond in the hot plate test on day 4 or 7 of treatment, however, formalin-evoked nociceptive behaviour was significantly increased in IFN-α treated mice following 8 days of IFN-α administration. 2-Arachidonoyl glycerol (2-AG) levels in the periaqueductal grey (PAG) and rostroventromedial medulla (RVM), and anandamide (AEA) levels in the RVM, were significantly increased in IFN-α-, but not saline-, treated mice following formalin administration. There was no change in endocannabinoid levels in the prefrontal cortex, spinal cord or paw tissue between saline- or IFNα-treated mice in the presence or absence of formalin. Furthermore, repeated IFN-α and/or formalin administration did not alter mRNA expression of genes encoding the endocannabinoid catabolic enzymes (fatty acid amide hydrolase or monoacylglycerol lipase) or endocannabinoid receptor targets (CB1, CB2 or PPARs) in the brain, spinal cord or paw tissue. Intra plantar administration of PF3845 (1 µg/10 µl) or MJN110 (1 µg/10 µl), inhibitors of AEA and 2-AG catabolism respectively, attenuated formalin-evoked hyperalgesia in IFN-α, but not saline-, treated mice. In summary, increasing peripheral endocannabinoid tone attenuates inflammatory hyperalgesia induced following repeated IFN-α administration. These data provide support for the endocannabinoid system in mediating and modulating heightened pain responding associated with IFNα-induced depression.

A practical computerized decision support system for predicting the severity of Alzheimer's disease of an individual.

Computerized clinical decision support systems can help to provide objective, standardized, and timely dementia diagnosis. However, current computerized systems are mainly based on group analysis, discrete classification of disease stages, or expensive and not readily accessible biomarkers, while current clinical practice relies relatively heavily on cognitive and functional assessments (CFA). In this study, we developed a computational framework using a suite of machine learning tools for identifying key markers in predicting the severity of Alzheimer's disease (AD) from a large set of biological and clinical measures. Six machine learning approaches, namely Kernel Ridge Regression (KRR), Support Vector Regression, and k-Nearest Neighbor for regression and Support Vector Machine (SVM), Random Forest, and k-Nearest Neighbor for classification, were used for the development of predictive models. We demonstrated high predictive power of CFA. Predictive performance of models incorporating CFA was shown to consistently have higher accuracy than those based solely on biomarker modalities. We found that KRR and SVM were the best performing regression and classification methods respectively. The optimal SVM performance was observed for a set of four CFA test scores (FAQ, ADAS13, MoCA, MMSE) with multi-class classification accuracy of 83.0%, 95%CI = (72.1%, 93.8%) while the best performance of the KRR model was reported with combined CFA and MRI neuroimaging data, i.e., R 2 = 0.874, 95%CI = (0.827, 0.922). Given the high predictive power of CFA and their widespread use in clinical practice, we then designed a data-driven and self-adaptive computerized clinical decision support system (CDSS) prototype for evaluating the severity of AD of an individual on a continuous spectrum. The system implemented an automated computational approach for data pre-processing, modelling, and validation and used exclusively the scores of selected cognitive measures as data entries. Taken together, we have developed an objective and practical CDSS to aid AD diagnosis.

FAAH, but not MAGL, inhibition modulates acute TLR3-induced neuroimmune signaling in the rat, independent of sex.

Toll-like receptor (TLR)3 is a key component of the innate immune response to viral infection. The present study firstly examined whether sex differences exist in TLR3-induced inflammatory, endocrine, and sickness responses. The data revealed that TLR3-induced expression of interferon- or NFkB-inducible genes (IFN-α/ß, IP-10, or TNF-α), either peripherally (spleen) or centrally (hypothalamus), did not differ between male and female rats, with the exception of TLR3-induced IFN-α expression in the spleen of female, but not male, rats 8 hr post TLR3 activation. Furthermore, TLR3 activation increased plasma corticosterone levels, induced fever, and reduced locomotor activity and body weight - effects independent of sex. Thus, the acute-phase inflammatory, endocrine, and sickness responses to TLR3 activation exhibit minimal sex-related differences. A further aim of this study was to examine whether enhancing endocannabinoid tone - namely, 2-arachidonylglycerol (2-AG) or N-arachidonoylethanolamine (AEA), exhibited similar effects on TLR3-induced inflammatory responses in male versus female rats. Systemic administration of the monoacylglycerol lipase (MAGL) inhibitor MJN110 and subsequent increases in 2-AG levels did not alter the TLR3-induced increase in IP-10, IRF7, or TNF-α expression in the spleen or the hypothalamus of male or female rats. In contrast, the fatty acid amide hydrolase (FAAH) inhibitor URB597 increased levels of AEA and related N-acylethanolamines, an effect associated with the attenuation of TLR3-induced inflammatory responses in the hypothalamus, but not the spleen, of male and female rats. These data support a role for FAAH, but not MAGL, substrates in the modulation of TLR3-induced neuroinflammatory responses, effects independent of sex.

Plasma N-acylethanolamine and endocannabinoid levels in burning mouth syndrome: Potential role in disease pathogenesis.

OBJECTIVE: The objective was to measure endocannabinoid (eCB) ligands and non-cannabinoid N-acylethanolamine (NAE) molecules in plasma from individuals with burning mouth syndrome (BMS) and to determine whether plasma eCB/NAE levels correlated with pain, inflammation and depressive symptomatology in this cohort. STUDY DESIGN: Plasma content of the eCBs, anandamide (AEA) and 2-arachidonoyl-glycerol (2-AG), and the NAE molecules, palmitoylethanolamide (PEA) and oleoylethanolamide (OEA) were assessed in healthy subjects (n = 8) and in a cohort of newly diagnosed BMS patients (n = 9) using liquid chromatography-tandem mass spectrometry. Plasma eCBs and NAE profiles were correlated with self-rated oral cavity pain intensities, depressive symptomatology and plasma IL-8 levels. RESULTS: Plasma levels of PEA, but not OEA, AEA or 2-AG, were significantly elevated in patients with BMS, when compared to plasma from healthy individuals. Plasma PEA, OEA and AEA levels correlated with depressive symptomatology. CONCLUSIONS: This is the first evidence to indicate that circulating eCB/NAE levels are altered in BMS.

Psychological stress in early life as a predisposing factor for the development of chronic pain: Clinical and preclinical evidence and neurobiological mechanisms.

A wealth of research over the past 2 decades has expanded our understanding of the impact of early-life adversity on physiological function and, consequently, health and wellbeing in later life. Early-life adversity increases the risk of developing a number of disorders, such as chronic pain, fibromyalgia, and irritable bowel syndrome. Although much of the research has examined the impact of physical maltreatment, an increasing number of studies have been published over the past few years examining the effect of childhood psychological stress and trauma on the development of various types of chronic pain conditions. We review the clinical and preclinical data examining the link among early-life psychological stress, altered nociceptive behavior, and chronic pain in later life. Evidence supporting a role for certain key neurobiological substrates, including the hypothalamic-pituitary-adrenal axis; monoaminergic, opioidergic, endocannabinoid and immune systems; and epigenetic mechanisms in the association between early-life psychological stress and chronic pain, is provided. Greater understanding of the impact of early-life stress may inform the development of personalized treatments for chronic pain in later life and strategies to prevent its onset in susceptible individuals. © 2016 Wiley Periodicals, Inc.

Pharmacological inhibition of FAAH modulates TLR-induced neuroinflammation, but not sickness behaviour: An effect partially mediated by central TRPV1.

Aberrant activation of toll-like receptors (TLRs), key components of the innate immune system, has been proposed to underlie and exacerbate a range of central nervous system disorders. Increasing evidence supports a role for the endocannabinoid system in modulating inflammatory responses including those mediated by TLRs, and thus this system may provide an important treatment target for neuroinflammatory disorders. However, the effect of modulating endocannabinoid tone on TLR-induced neuroinflammation in vivo and associated behavioural changes is largely unknown. The present study examined the effect of inhibiting fatty acid amide hydrolyase (FAAH), the primary enzyme responsible for the metabolism of anandamide (AEA), in vivo on TLR4-induced neuroimmune and behavioural responses, and evaluated sites and mechanisms of action. Systemic administration of the FAAH inhibitor PF3845 increased levels of AEA, and related FAAH substrates N-oleoylethanolamide (OEA) and N-palmitoylethanolamide (PEA), in the frontal cortex and hippocampus of rats, an effect associated with an attenuation in the expression of pro- and anti-inflammatory cytokines and mediators measured 2hrs following systemic administration of the TLR4 agonist, lipopolysaccharide (LPS). These effects were mimicked by central i.c.v. administration of PF3845, but not systemic administration of the peripherally-restricted FAAH inhibitor URB937. Central antagonism of TRPV1 significantly attenuated the PF3845-induced decrease in IL-6 expression, effects not observed following antagonism of CB1, CB2, PPARα, PPARγ or GPR55. LPS-induced a robust sickness-like behavioural response and increased the expression of markers of glial activity and pro-inflammatory cytokines over 24hrs. Systemic administration of PF3845 modulated the TLR4-induced expression of neuroimmune mediators and anhedonia without altering acute sickness behaviour. Overall, these findings support an important role for FAAH substrates directly within the brain in the regulation of TLR4-associated neuroinflammation and highlight a role for TRPV1 in partially mediating these effects.

Genotype-dependent responsivity to inflammatory pain: A role for TRPV1 in the periaqueductal grey.

Negative affective state has a significant impact on pain, and genetic background is an important moderating influence on this interaction. The Wistar-Kyoto (WKY) inbred rat strain exhibits a stress-hyperresponsive, anxiety/depressive-like phenotype and also displays a hyperalgesic response to noxious stimuli. Transient receptor potential subfamily V member 1 (TRPV1) within the midbrain periaqueductal grey (PAG) plays a key role in regulating both aversive and nociceptive behaviour. In the present study, we investigated the role of TRPV1 in the sub-columns of the PAG in formalin-evoked nociceptive behaviour in WKY versus Sprague-Dawley (SD) rats. TRPV1 mRNA expression was significantly lower in the dorsolateral (DL) PAG and higher in the lateral (L) PAG of WKY rats, compared with SD counterparts. There were no significant differences in TRPV1 mRNA expression in the ventrolateral (VL) PAG between the two strains. TRPV1 mRNA expression significantly decreased in the DLPAG and increased in the VLPAG of SD, but not WKY rats upon intra-plantar formalin administration. Intra-DLPAG administration of either the TRPV1 agonist capsaicin, or the TRPV1 antagonist 5'-Iodoresiniferatoxin (5'-IRTX), significantly increased formalin-evoked nociceptive behaviour in SD rats, but not in WKY rats. The effects of capsaicin were likely due to TRPV1 desensitisation, given their similarity to the effects of 5'-IRTX. Intra-VLPAG administration of capsaicin or 5'-IRTX reduced nociceptive behaviour in a moderate and transient manner in SD rats, and similar effects were seen with 5'-IRTX in WKY rats. Intra-LPAG administration of 5'-IRTX reduced nociceptive behaviour in a moderate and transient manner in SD rats, but not in WKY rats. These results indicate that modulation of inflammatory pain by TRPV1 in the PAG occurs in a sub-column-specific manner. The data also provide evidence for differences in the expression of TRPV1, and differences in the effects of pharmacological modulation of TRPV1 in specific PAG sub-columns, between WKY and SD rats, suggesting that TRPV1 expression and/or functionality in the PAG plays a role in hyper-responsivity to noxious stimuli in a genetic background prone to negative affect.

CB1 and CB2 cannabinoid receptor antagonists prevent minocycline-induced neuroprotection following traumatic brain injury in mice.

Traumatic brain injury (TBI) and its consequences represent one of the leading causes of death in young adults. This lesion mediates glial activation and the release of harmful molecules and causes brain edema, axonal injury, and functional impairment. Since glial activation plays a key role in the development of this damage, it seems that controlling it could be beneficial and could lead to neuroprotective effects. Recent studies show that minocycline suppresses microglial activation, reduces the lesion volume, and decreases TBI-induced locomotor hyperactivity up to 3 months. The endocannabinoid system (ECS) plays an important role in reparative mechanisms and inflammation under pathological situations by controlling some mechanisms that are shared with minocycline pathways. We hypothesized that the ECS could be involved in the neuroprotective effects of minocycline. To address this hypothesis, we used a murine TBI model in combination with selective CB1 and CB2 receptor antagonists (AM251 and AM630, respectively). The results provided the first evidence for the involvement of ECS in the neuroprotective action of minocycline on brain edema, neurological impairment, diffuse axonal injury, and microglial activation, since all these effects were prevented by the CB1 and CB2 receptor antagonists.

High Times for Painful Blues: The Endocannabinoid System in Pain-Depression Comorbidity.

Depression and pain are two of the most debilitating disorders worldwide and have an estimated cooccurrence of up to 80%. Comorbidity of these disorders is more difficult to treat, associated with significant disability and impaired health-related quality of life than either condition alone, resulting in enormous social and economic cost. Several neural substrates have been identified as potential mediators in the association between depression and pain, including neuroanatomical reorganization, monoamine and neurotrophin depletion, dysregulation of the hypothalamo-pituitary-adrenal axis, and neuroinflammation. However, the past decade has seen mounting evidence supporting a role for the endogenous cannabinoid (endocannabinoid) system in affective and nociceptive processing, and thus, alterations in this system may play a key role in reciprocal interactions between depression and pain. This review will provide an overview of the preclinical evidence supporting an interaction between depression and pain and the evidence supporting a role for the endocannabinoid system in this interaction.

Pretreatment anxiety and pain acceptance are associated with response to trigger point injection therapy for chronic myofascial pain.

BACKGROUND AND AIM: This study examined the psychosocial profile of patients who responded or did not respond to trigger point injection therapy for chronic myofascial pain. METHODS: Seventy one patients with a diagnosis of chronic myofascial pain of the paraspinous muscles completed a pretreatment questionnaire measuring demographic and social factors, and validated scales to assess pain intensity, pain interference (physical and emotional), and defined psychological characteristics (pain catastrophizing, pain acceptance, pain self-efficacy, mood and anxiety). Trigger point injection therapy of the affected areas of myofascial pain was performed and follow-up was conducted by telephone at one week (n = 65) and one month (n = 63) post intervention to assess treatment outcome (pain intensity and pain-related physical interference). RESULTS: At one week follow-up and one-month follow-up, using pain-related physical interference as the outcome measure, we found that those who responded well to treatment were characterized by a lower level of pretreatment anxiety and a higher level of pain acceptance, with anxiety being the strongest predictor. CONCLUSION: These results suggest that responses to interventional pain management in chronic myofascial paraspinous pain may be influenced by psychological characteristics, especially pretreatment anxiety.

Microinjection of 2-arachidonoyl glycerol into the rat ventral hippocampus differentially modulates contextually induced fear, depending on a persistent pain state.

The endogenous cannabinoid (endocannabinoid) system plays a key role in the modulation of aversive and nociceptive behaviour. The components of the endocannabinoid system are expressed throughout the hippocampus, a brain region implicated in both conditioned fear and pain. In light of evidence that pain can impact on the expression of fear-related behaviour, and vice versa, we hypothesised that exogenous administration of the endocannabinoid 2-arachidonoyl glycerol (2-AG) into the ventral hippocampus (vHip) would differentially regulate fear responding in the absence vs. the presence of formalin-evoked nociceptive tone. Fear-conditioned rats showed significantly increased freezing and a reduction in formalin-evoked nociceptive behaviour upon re-exposure to a context previously paired with footshock. Bilateral microinjection of 2-AG into the vHip significantly reduced contextually induced freezing in non-formalin-treated rats, and reduced formalin-evoked nociceptive behaviour in non-fear-conditioned rats. In contrast, 2-AG microinjection had no effect on fear responding in formalin-treated rats, and no effect on nociceptive behaviour in fear-conditioned rats. The inhibitory effect of 2-AG on fear-related behaviour, but not pain-related behaviour, was blocked by co-administration of the cannabinoid receptor 1 (CB1) antagonist/inverse agonist rimonabant. Tissue levels of the endocannabinoids N-arachidonoylethanolamide (anandamide, AEA) and 2-AG were similar in the vHip of fear-conditioned rats receiving formalin injection and the vHip of fear-conditioned rats receiving saline injection. However, the levels of AEA and 2-AG were significantly lower in the contralateral ventrolateral periaqueductal grey of formalin-treated fear-conditioned rats than in that of their saline-treated counterparts. These data suggest that 2-AG-CB1 receptor signalling in the vHip has an anti-aversive effect, and that this effect is abolished in the presence of a persistent pain state.

Minocycline modulates neuropathic pain behaviour and cortical M1-M2 microglial gene expression in a rat model of depression.

There is a paucity of data on the role of microglia and neuroinflammatory processes in the association between chronic pain and depression. The current study examined the effect of the microglial inhibitor minocycline on depressive-like behaviour, spinal nerve ligation (SNL)-induced mechanical and cold allodynia and associated changes in the expression of genes encoding microglial markers (M1 vs. M2 polarisation) and inflammatory mediators in the prefrontal cortex in the olfactory bulbectomised (OB) rat model of depression. Acute minocycline administration did not alter OB-induced depressive-like behaviour but prevented SNL-induced mechanical allodynia in both OB and sham rats. In comparison, chronic minocycline attenuated OB-induced depressive-like behaviour and prevented the development of SNL-induced mechanical allodynia in OB, but not sham, rats. Further analysis revealed that SNL-induced mechanical allodynia in OB rats was attenuated by chronic minocycline at almost all time-points over a 2week testing period, an effect observed only from day 10 post-SNL in sham rats. Chronic administration of minocycline reduced the expression of CD11b, a marker of microglial activation, and the M1 pro-inflammatory cytokine IL-1ß, in the prefrontal cortex of sham-SNL animals. In comparison, the expression of the M2 microglia marker (MRC2) and anti-inflammatory cytokine IL-10 was increased, as were IL-1ß, IL-6 and SOCS3, in the prefrontal cortex of OB-SNL animals following chronic minocycline. Thus, chronic minocycline attenuates neuropathic pain behaviour and modulates microglial activation and the central expression of inflammatory mediators in a manner dependent on the presence or absence of a depressive-like phenotype.