Alterations in Skeletal Muscle Insulin Signaling DNA Methylation: A Pilot Randomized Controlled Trial of Olanzapine in Healthy Volunteers.

Antipsychotics are associated with severe metabolic side effects including insulin resistance; however, the mechanisms underlying this side effect are not fully understood. The skeletal muscle plays a critical role in insulin-stimulated glucose uptake, and changes in skeletal muscle DNA methylation by antipsychotics may play a role in the development of insulin resistance. A double-blind, placebo-controlled trial of olanzapine was performed in healthy volunteers. Twelve healthy volunteers were randomized to receive 10 mg/day of olanzapine for 7 days. Participants underwent skeletal muscle biopsies to analyze DNA methylation changes using a candidate gene approach for the insulin signaling pathway. Ninety-seven methylation sites were statistically significant (false discovery rate < 0.05 and beta difference between the groups of ≥10%). Fifty-five sites had increased methylation in the skeletal muscle of olanzapine-treated participants while 42 were decreased. The largest methylation change occurred at a site in the Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-Alpha (PPARGC1A) gene, which had 52% lower methylation in the olanzapine group. Antipsychotic treatment in healthy volunteers causes significant changes in skeletal muscle DNA methylation in the insulin signaling pathway. Future work will need to expand on these findings with expression analyses.

Metabolomics, Lipidomics, and Antipsychotics: A Systematic Review.

Antipsychotics are an important pharmacotherapy option for the treatment of many mental illnesses. Unfortunately, selecting antipsychotics is often a trial-and-error process due to a lack of understanding as to which medications an individual patient will find most effective and best tolerated. Metabolomics, or the study of small molecules in a biosample, is an increasingly used omics platform that has the potential to identify biomarkers for medication efficacy and toxicity. This systematic review was conducted to identify metabolites and metabolomic pathways associated with antipsychotic use in humans. Ultimately, 42 studies were identified for inclusion in this review, with all but three studies being performed in blood sources such as plasma or serum. A total of 14 metabolite classes and 12 lipid classes were assessed across studies. Although the studies were highly heterogeneous in approach and mixed in their findings, increases in phosphatidylcholines, decreases in carboxylic acids, and decreases in acylcarnitines were most consistently noted as perturbed in patients exposed to antipsychotics. Furthermore, for the targeted metabolomic and lipidomic studies, seven metabolites and three lipid species had findings that were replicated. The most consistent finding for targeted studies was an identification of a decrease in aspartate with antipsychotic treatment. Studies varied in depth of detail provided for their study participants and in study design. For example, in some cases, there was a lack of detail on specific antipsychotics used or concomitant medications, and the depth of detail on sample handling and analysis varied widely. The conclusions here demonstrate that there is a large foundation of metabolomic work with antipsychotics that requires more complete reporting so that an objective synthesis such as a meta-analysis can take place. This will then allow for validation and clinical application of the most robust findings to move the field forward. Future studies should be carefully controlled to take advantage of the sensitivity of metabolomics while limiting potential confounders that may result from participant heterogeneity and varied analysis approaches.

The Development of Posttraumatic Stress Disorder and Depression Symptoms in Iraqi Refugees: Associations with Acculturation and C-reactive Protein.

ABSTRACT: Refugees experience distress from premigration trauma, often exacerbated by postmigration difficulties. To develop effective interventions, risk factors for mental health symptoms need to be determined. Male Iraqi refugees (N = 53) to the United States provided background information and reported predisplacement trauma and psychological health within 1 month of their arrival. An inflammatory biomarker-C-reactive protein (CRP) was assessed approximately 1.5 years after arrival, and a contextual factor-acculturation-and psychological health were assessed 2 years after arrival. We tested whether acculturation and CRP were associated with posttraumatic stress disorder (PTSD) and depression symptoms at the 2-year follow-up, controlling for baseline symptoms, age, body mass index, and predisplacement trauma. Acculturation was inversely related to depression, and CRP was positively related to both PTSD and depression at the 2-year follow-up. Interventions targeting acculturation could help reduce the development of depression symptoms in refugees. The role of CRP in the development of PTSD and depression symptoms warrants further research.

C-reactive Protein Levels in Plasma and Chronic Venous Ulcer Exudate of Persons Who Inject Drugs: A Pilot Study.

BACKGROUND: Persons who inject drugs (PWID) in the groin, legs, and/or feet are at high risk for chronic venous ulcers (CVUs). The plasma C-reactive protein (CRP) level is a marker of systemic inflammation. OBJECTIVE: This pilot study examined CRP levels in plasma and CVU exudate of PWID. The aims were to (1) compare levels of CRP in plasma and exudate; (2) examine if the CRP level in exudate changed over 4 weeks with wound treatment; and (3) examine the relationship of the exudate CRP level with CVU area, CVU age, number of CVUs, and number of comorbidities. MATERIALS AND METHODS: Persons who inject drugs seeking wound care were enrolled in this Institutional Review Board approved prospective, longitudinal, descriptive study. A blood sample was collected on the first visit (week 1); the plasma was then separated. Wound exudate was collected on swabs during the first visit (week 1) and 4 weeks later (week 4). All samples were stored at -80° C. Samples were eluted from swabs using mass spectrometry grade water then aliquoted for CRP analysis. RESULTS: The participants of the study included 14 PWID (mean age, 62.14 ± 4.52 years; mean number of comorbidities, 5.71 ± 1.90; and mean number of ulcers 2.07 ± 1.07 that were present for a mean of 7.96 ± 11.91 years without healing). C-reactive protein level in plasma was a mean of 6.47 ± 8.56 mg/L, with lower levels found in wound exudate but highly correlated (rho = .925). Exudate CRP levels decreased from week 1 to week 4, and the 2 were highly correlated (rho = .895). Exudate CRP level week 1 was not significantly related to wound area, wound age, number of ulcers, or number of comorbidities. CONCLUSIONS: Plasma and exudate CRP levels were highly correlated. Exudate CRP levels decreased across time. Future large-scale wound healing studies should examine CRP levels over a longer duration and as they correlate to wound healing.

Personal genotyping and student outcomes in genetic and pharmacogenetic teaching: a systematic review and meta-analysis.

Aim: Teaching of genetics and pharmacogenetics with personal genotyping (PGT) is becoming commonplace. We aimed to perform a systematic review and meta-analysis to understand the effects of PGT on student outcomes. Methods: A systematic review was performed on studies that reported the effects of PGT on student attitudes, perceptions or knowledge. Extracted data were summarized qualitatively and when possible, quantitatively. Results: Student PGT has a positive effect on student attitude and perceptions survey responses in studies without a control group (p = 0.009) and in studies with a control group (p = 0.025). Knowledge increased after the use of PGT (p < 0.001) in studies without a control group. Conclusion: The findings here suggest that perceptions, attitudes and knowledge increase with PGT in the classroom.

Bibliometric data based on the Pharm.D. and Ph.D. degree in United States research-intensive colleges of pharmacy.

OBJECTIVES: The objective of this work was to compare bibliometrics based on doctoral degrees within United States colleges of pharmacy to understand productivity differences. Secondary objectives were to provide quantitative data based on degree that could be utilized by individual faculty, administration and other key stakeholders in academic pharmacy. METHODS: Bibliometric indices were obtained from Scopus and Web of Science for faculty from research-intensive United States pharmacy schools. Scholarly metrics that included publication number, total citations, highest cited article and H-index were compared between degrees using multivariate regression adjusted for academic rank and years since first publication. A correction for multiple testing was applied. KEY FINDINGS: All collected scholarly metrics were higher for Ph.D.-only and Pharm.D./Ph.D. faculty when compared to Pharm.D.-only faculty. Ph.D.-only faculty significantly differed compared to Pharm.D./Ph.D. faculty for Web of Science average citations per document. CONCLUSIONS: Differences are apparent between the major doctoral degrees at research-intensive, federally funded colleges of pharmacy; however, these differences were primarily identified for Pharm.D.-only compared to the other doctoral degree types Future work should analyse the potential variables that explain the scholarly metrics differences between degrees and aim to analyse other areas of faculty impact beyond scholarly metrics.

A bibliometric analysis of the top 50 NIH-Funded colleges of pharmacy using two databases.

BACKGROUND: Scholarly productivity is an essential component of college of pharmacy activities and may depend on university rank, faculty type, faculty rank and department. Bibliometric measures provide a means to analyze scholarly productivity from colleges of pharmacy while accounting for these various factors. OBJECTIVES: To analyze bibliometric data from two databases based on Carnegie Research Classification and NIH-funding rank; provide descriptions of bibliometric data based on department type and faculty classification; and examine the distribution of publications in the top 50 NIH-funded Colleges of Pharmacy. METHODS: Faculty rosters were gathered for the top 50 NIH-funded colleges of pharmacy, and names were searched in Scopus and Web of Science to establish bibliometric records. Bibliometric indices were compared based on Carnegie Basic Classification and between the NIH funding ranks 1-25 versus 26-50 using WOS bibliometric data. Descriptive statistics were presented, and Pareto distributions were developed for total publications across all schools included. RESULTS: Schools in the top 25 for NIH funding and schools with a Carnegie R1 classification had significantly higher bibliometric measures compared to schools ranked 26-50 and schools classified as R2, respectively. For faculty members with a bibliometric record (i.e., at least one publication), 20% provide approximately 60% of the publications. Additionally, approximately 90% of publications are provided by 50% of faculty records. Faculty records from basic science departments, as compared to clinical pharmacy departments, represent the highest contributing groups in the Pareto analysis. CONCLUSION: Bibliometric indices are higher at colleges of pharmacy with greater NIH funding or an R1 Carnegie classification. A minority of faculty provides most publications in colleges of pharmacy, which is composed of members from basic science departments. The descriptive data provided here is useful for understanding readily available bibliometric data based on department type and faculty classification and rank.

Atypical antipsychotics, insulin resistance and weight; a meta-analysis of healthy volunteer studies.

Atypical antipsychotics increase the risk of diabetes and cardiovascular disease through their side effects of insulin resistance and weight gain. The populations for which atypical antipsychotics are used carry a baseline risk of metabolic dysregulation prior to medication which has made it difficult to fully understand whether atypical antipsychotics cause insulin resistance and weight gain directly. The purpose of this work was to conduct a systematic review and meta-analysis of atypical antipsychotic trials in healthy volunteers to better understand their effects on insulin sensitivity and weight gain. Furthermore, we aimed to evaluate the occurrence of insulin resistance with or without weight gain and with treatment length by using subgroup and meta-regression techniques. Overall, the meta-analysis provides evidence that atypical antipsychotics decrease insulin sensitivity (standardized mean difference=-0.437, p<0.001) and increase weight (standardized mean difference=0.591, p<0.001) in healthy volunteers. It was found that decreases in insulin sensitivity were potentially dependent on treatment length but not weight gain. Decreases in insulin sensitivity occurred in multi-dose studies <13days while weight gain occurred in studies 14days and longer (max 28days). These findings provide preliminary evidence that atypical antipsychotics cause insulin resistance and weight gain directly, independent of psychiatric disease and may be associated with length of treatment. Further, well-designed studies to assess the co-occurrence of insulin resistance and weight gain and to understand the mechanisms and sequence by which they occur are required.

Endogenous Opioid Mechanisms Are Implicated in Obesity and Weight Loss in Humans.

CONTEXT: Successful long-term weight loss is challenging. Brain endogenous opioid systems regulate associated processes; however, their role in the maintenance of weight loss has not been adequately explored in humans. OBJECTIVE: In a preliminary study, the objective was to assess central µ-opioid receptor (MOR) system involvement in eating behaviors and their relationship to long-term maintenance of weight loss. DESIGN: This was a case-control study with follow-up of the treatment group at 1 year after intervention. SETTING: The study was conducted at a tertiary care university medical center. PARTICIPANTS: Lean healthy (n = 7) and chronically obese (n = 7) men matched for age and ethnicity participated in the study. INTERVENTIONS: MOR availability measures were acquired with positron emission tomography and [(11)C]carfentanil. Lean healthy men were scanned twice under both fasted and fed conditions. Obese men were placed on a very low-calorie diet to achieve 15% weight loss from baseline weight and underwent two positron emission tomography scans before and two after weight loss, incorporating both fasted and fed states. MAIN OUTCOME MEASURES: Brain MOR availability and activation were measured by reductions in MOR availability (nondisplaceable binding potential) from the fed compared with the fasted-state scans. RESULTS: Baseline MOR nondisplaceable binding potential was reduced in obese compared with the lean and partially recovered obese after weight loss in regions that regulate homeostatic, hedonic, and emotional responses to feeding. Reductions in negative affect and feeding-induced MOR system activation in the right temporal pole were highly correlated in leans but not in obese men. A trend for an association between MOR activation in the right temporal pole before weight loss and weight regain 1 year was found. CONCLUSIONS: Although these preliminary studies have a small sample size, these results suggest that obesity and diet-induced weight loss impact central MOR binding and endogenous opioid system function. MOR system activation in response to an acute meal may be related to the risk of weight regain.

Individual Differences in Cue-Induced Motivation and Striatal Systems in Rats Susceptible to Diet-Induced Obesity.

Pavlovian cues associated with junk-foods (caloric, highly sweet, and/or fatty foods), like the smell of brownies, can elicit craving to eat and increase the amount of food consumed. People who are more susceptible to these motivational effects of food cues may have a higher risk for becoming obese. Further, overconsumption of junk-foods leading to the development of obesity may itself heighten attraction to food cues. Here, we used a model of individual susceptibility to junk-foods diet-induced obesity to determine whether there are pre-existing and/or diet-induced increases in attraction to and motivation for sucrose-paired cues (ie, incentive salience or 'wanting'). We also assessed diet- vs obesity-associated alterations in mesolimbic function and receptor expression. We found that rats susceptible to diet-induced obesity displayed heightened conditioned approach prior to the development of obesity. In addition, after junk-food diet exposure, those rats that developed obesity also showed increased willingness to gain access to a sucrose cue. Heightened 'wanting' was not due to individual differences in the hedonic impact ('liking') of sucrose. Neurobiologically, Mu opioid receptor mRNA expression was lower in striatal 'hot-spots' that generate eating or hedonic impact only in those rats that became obese. In contrast, prolonged exposure to junk-food resulted in cross-sensitization to amphetamine-induced locomotion and downregulation of striatal D2R mRNA regardless of the development of obesity. Together these data shed light on individual differences in behavioral and neurobiological consequences of exposure to junk-food diets and the potential contribution of incentive sensitization in susceptible individuals to greater food cue-triggered motivation.

Leptin regulates dopamine responses to sustained stress in humans.

Neural systems that identify and respond to salient stimuli are critical for survival in a complex and changing environment. In addition, interindividual differences, including genetic variation and hormonal and metabolic status likely influence the behavioral strategies and neuronal responses to environmental challenges. Here, we examined the relationship between leptin allelic variation and plasma leptin levels with DAD2/3R availability in vivo as measured with [(11)C]raclopride PET at baseline and during a standardized pain stress challenge. Allelic variation in the leptin gene was associated with varying levels of dopamine release in response to the pain stressor, but not with baseline D2/3 receptor availability. Circulating leptin was also positively associated with stress-induced dopamine release. These results show that leptin serves as a regulator of neuronal function in humans and provides an etiological mechanism for differences in dopamine neurotransmission in response to salient stimuli as related to metabolic function. The capacity for leptin to influence stress-induced dopaminergic function is of importance for pathological states where dopamine is thought to play an integral role, such as mood, substance-use disorders, eating disorders, and obesity.

Brain activation patterns at exhaustion in rats that differ in inherent exercise capacity.

In order to further understand the genetic basis for variation in inherent (untrained) exercise capacity, we examined the brains of 32 male rats selectively bred for high or low running capacity (HCR and LCR, respectively). The aim was to characterize the activation patterns of brain regions potentially involved in differences in inherent running capacity between HCR and LCR. Using quantitative in situ hybridization techniques, we measured messenger ribonuclease (mRNA) levels of c-Fos, a marker of neuronal activation, in the brains of HCR and LCR rats after a single bout of acute treadmill running (7.5-15 minutes, 15° slope, 10 m/min) or after treadmill running to exhaustion (15-51 minutes, 15° slope, initial velocity 10 m/min). During verification of trait differences, HCR rats ran six times farther and three times longer prior to exhaustion than LCR rats. Running to exhaustion significantly increased c-Fos mRNA activation of several brain areas in HCR, but LCR failed to show significant elevations of c-Fos mRNA at exhaustion in the majority of areas examined compared to acutely run controls. Results from these studies suggest that there are differences in central c-Fos mRNA expression, and potential brain activation patterns, between HCR and LCR rats during treadmill running to exhaustion and these differences could be involved in the variation in inherent running capacity between lines.

The use of a running wheel to measure activity in rodents: relationship to energy balance, general activity, and reward.

Running wheels are commonly employed to measure rodent physical activity in a variety of contexts, including studies of energy balance and obesity. There is no consensus on the nature of wheel-running activity or its underlying causes, however. Here, we will begin by systematically reviewing how running wheel availability affects physical activity and other aspects of energy balance in laboratory rodents. While wheel running and physical activity in the absence of a wheel commonly correlate in a general sense, in many specific aspects the two do not correspond. In fact, the presence of running wheels alters several aspects of energy balance, including body weight and composition, food intake, and energy expenditure of activity. We contend that wheel-running activity should be considered a behavior in and of itself, reflecting several underlying behavioral processes in addition to a rodent's general, spontaneous activity. These behavioral processes include defensive behavior, predatory aggression, and depression- and anxiety-like behaviors. As it relates to energy balance, wheel running engages several brain systems-including those related to the stress response, mood, and reward, and those responsive to growth factors-that influence energy balance indirectly. We contend that wheel-running behavior represents factors in addition to rodents' tendency to be physically active, engaging additional neural and physiological mechanisms which can then independently alter energy balance and behavior. Given the impact of wheel-running behavior on numerous overlapping systems that influence behavior and physiology, this review outlines the need for careful design and interpretation of studies that utilize running wheels as a means for exercise or as a measurement of general physical activity.

Risk-assessment and coping strategies segregate with divergent intrinsic aerobic capacity in rats.

Metabolic function is integrally related to an individual's susceptibility to, and progression of, disease. Selective breeding for intrinsic treadmill running in rats has produced distinct lines of high- or low-capacity runners (HCR and LCR, respectively) that exhibit numerous physiological differences. To date, the role of intrinsic aerobic capacity on behavior and stress response in these rats has not been addressed and was the focus of these studies. HCR and LCR rats did not differ in their locomotor response to novelty or behavior in the light/dark box. In contrast, immobility in the forced swim test was higher in LCR rats compared with HCR rats, regardless of desipramine treatment. Although both HCR and LCR rats responded to cat odor with decreased exploration and increased risk assessment, HCR rats showed greater contextual conditioning to cat odor. HCR rats exhibited higher expression of corticotropin-releasing hormone in the central nucleus of the amygdala, as well as heavier adrenal and thymus weight. Corticosterone was comparable among HCR and LCR rats at light/dark transitions, and in response to unavoidable cat odor. HCR rats, however, exhibited a greater corticosterone response following the light/dark box. These experiments show that the LCR phenotype associates with decreased risk assessment in response to salient danger signals and passive coping. In contrast, HCR rats show a more naturalistic strategy in that they employ active coping and a more vigilant and cautious response to environmental novelty and salient danger signals. Within this context, we propose that intrinsic aerobic capacity is a central feature mechanistically linking complex metabolic disease and behavior.

Dietary n-3:n-6 fatty acid ratios differentially influence hormonal signature in a rodent model of metabolic syndrome relative to healthy controls.

Dietary ratios of omega-3 (n-3) to omega-6 (n-6) polyunsaturated fatty acids (PUFAs) have been implicated in controlling markers of the metabolic syndrome, including insulin sensitivity, inflammation, lipid profiles and adiposity. However, the role of dietary PUFAs in regulating energy systems in healthy relative to metabolic diseased backgrounds has not been systematically addressed. We used dietary manipulation of n-3 to n-6 PUFA ratios in an animal model of metabolic syndrome and a related healthy line to assay feeding behavior and endocrine markers of feeding drive and energy regulation. Two related lines of rodents with a healthy and a metabolic syndrome phenotype were fed one of two isocaloric diets, comprised of either a 1:1 or a 1:30 n-3 to n-6 ratio, for 30 days. Food intake and weight gain were monitored; and leptin, ghrelin, adiponectin and a suite of hypothalamic neuropeptides involved in energy regulation were assayed following the dietary manipulation period. There was no difference in caloric intake or weight gain between diet groups, however there was a significant interaction between diet and phenotypic line on central and peripheral markers of energy homeostasis. Thus serum levels of leptin, acylated-ghrelin and adiponectin, and mRNA levels of the anorexigenic hypothalamic neuropeptide, cocaine-amphetamine related transcript (CART), showed differential, dietary responses with HCR rats showing an increase in anorexigenic signals in response to unbalanced n-3:6 ratios, while LCR did not. These data are the first to demonstrate that a rodent line with a metabolic syndrome-like phenotype responds differentially to dietary manipulation of n-3 and n-6 fatty acids relative to a related healthy line with regard to endocrine markers of energy homeostasis. The dietary n-3:n-6 ratios used in this experiment represent extreme points of natural human diets, however the data suggest that optimal recommendations regarding omega-3 and omega-6 intake may have differing effects in healthy subjects relative to metabolic syndrome patients. Further research is necessary to establish these responses in human populations.

Spontaneous activity, economy of activity, and resistance to diet-induced obesity in rats bred for high intrinsic aerobic capacity.

Though obesity is common, some people remain resistant to weight gain even in an obesogenic environment. The propensity to remain lean may be partly associated with high endurance capacity along with high spontaneous physical activity and the energy expenditure of activity, called non-exercise activity thermogenesis (NEAT). Previous studies have shown that high-capacity running rats (HCR) are lean compared to low-capacity runners (LCR), which are susceptible to cardiovascular disease and metabolic syndrome. Here, we examine the effect of diet on spontaneous activity and NEAT, as well as potential mechanisms underlying these traits, in rats selectively bred for high or low intrinsic aerobic endurance capacity. Compared to LCR, HCR were resistant to the sizeable increases in body mass and fat mass induced by a high-fat diet; HCR also had lower levels of circulating leptin. HCR were consistently more active than LCR, and had lower fuel economy of activity, regardless of diet. Nonetheless, both HCR and LCR showed a similar decrease in daily activity levels after high-fat feeding, as well as decreases in hypothalamic orexin-A content. The HCR were more sensitive to the NEAT-activating effects of intra-paraventricular orexin-A compared to LCR, especially after high-fat feeding. Lastly, levels of cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C) in the skeletal muscle of HCR were consistently higher than LCR, and the high-fat diet decreased skeletal muscle PEPCK-C in both groups of rats. Differences in muscle PEPCK were not secondary to the differing amount of activity. This suggests the possibility that intrinsic differences in physical activity levels may originate at the level of the skeletal muscle, which could alter brain responsiveness to neuropeptides and other factors that regulate spontaneous daily activity and NEAT.

Upregulation of GAD65 mRNA in the medulla of the rat model of metabolic syndrome.

Metabolic syndrome is characterized by obesity, elevated blood pressure (BP), insulin resistance, and hypercholesterolemia. Recently an animal model of this disorder has been proposed in rats selectively bred based on their performance on a treadmill-running task. Accordingly, low capacity runner (LCR) rats exhibited all of the diagnostic criteria for metabolic syndrome, including elevated BP, as compared to their high capacity runner (HCR) counterparts [U. Wisløff, S.M. Najjar, O. Ellingsen, P.M. Haram, S. Swoap, Q. Al-Share, M. Fernstrom, K. Rezaei, S.J. Lee, L.G. Koch, S.L. Britton, Cardiovascular risk factors emerge after artificial selection for low aerobic capacity, Science 307 (2005) 418-420]. Previous studies have highlighted the importance of GABAergic neurotransmission in the medullary cardiovascular-regulatory areas in the central control of BP. Thus, we hypothesized a dysregulation in GABAergic transmission in the medullary cardiovascular-regulatory nuclei of LCR rats. To begin testing this hypothesis we carried out experiments examining expression of the GABA synthetic enzymes, GAD65 and GAD67, mRNAs in the two rat strains via radioactive in situ hybridization. Our results showed GAD65 and GAD67 mRNAs were widely expressed throughout the brainstem; quantification revealed increased GAD65 mRNA expression in LCR animals in the caudal nucleus tractus solitarius (NTS) and rostral ventrolateral medulla (VLM) as compared to HCR rats. Conversely, no differences in the expression of GAD67 were detected in these regions. These data are consistent with the notion of altered GABAergic neurotransmission in the NTS and VLM in metabolic syndrome, and point to the importance of these regions in cardiovascular regulation.

Alterations in fear conditioning and amygdalar activation following chronic wheel running in rats.

Several convergent lines of evidence point to the amygdala as a key site of plasticity underlying most forms of fear conditioning. Studies have shown that chronic physical activity, such as wheel running, can alter learning in a variety of contexts, including aversive conditioning. The ability of chronic wheel running (WR) to alter both behavioral correlates of fear conditioning and indices of amygdalar activation, however, has not been simultaneously assessed. Here, rats were given constant access to either free-turning or--as a control--locked (LC) running wheels in their home cages. After 8 weeks of housing under these conditions, animals were exposed to a series of shocks in a separate testing chamber. Twenty-four hours later, the animals were returned to the shock chamber and freezing behavior was measured as an indicator of contextual fear conditioning. The animals were then sacrificed and their brains processed for immunohistochemical detection of Fos to assess patterns of putative neuronal activation. WR rats spent significantly more time freezing than their LC counterparts upon return to the shock-paired context. The enhanced conditioned freezing response was most pronounced in animals showing high levels of nightly wheel running activity. WR animals also had significantly higher levels of neuronal activation, as indicated by Fos expression in the central nucleus of the amygdala, but less activation in the basolateral nucleus, compared to sedentary controls. These data demonstrate the ability of chronic physical activity to alter contextual fear conditioning and implicate the amygdala as a potential site of plasticity underlying this phenomenon.

Microinjection of naltrexone into the central, but not the basolateral, amygdala blocks the anxiolytic effects of diazepam in the plus maze.

The amygdala is involved in behavioral and physiological responses to fear, and the anxiolytic properties of several drugs are localized to this region. Activation of endogenous opioid systems is known to occur in response to stress and a growing body of literature suggests that opioid systems regulate the properties of anxiolytic drugs. These experiments sought to elucidate the role of opioid receptors in the central (CeA) and basolateral (BLA) nuclei of the amygdala in regulating the anxiolytic properties of ethanol and diazepam. Male rats fitted with cannula received bilateral microinjections of the nonselective opioid receptor antagonist naltrexone (NAL) immediately followed by systemic delivery of either ethanol (1 g/kg) or diazepam (2 mg/kg) in the elevated plus maze. Both diazepam and ethanol decreased anxiety-like behavior. Delivery of NAL into the CeA blocked the anxiolytic properties of diazepam. Delivery of NAL into the BLA slightly increased open arm avoidance, but had no effect on the anxiolytic properties of diazepam. Microinjection of NAL into either nucleus failed to block the effects of ethanol. These results were specific to the anxiolytic properties of diazepam, since baseline behaviors were unaffected by microinjection of NAL. Microinjection of lidocaine produced results distinct from NAL and failed to block the anxiolytic actions of diazepam. These studies indicate distinct roles for opioid receptor systems in the CeA and BLA in regulating the anxiolytic properties of diazepam in the elevated plus maze. Further, opioid receptor systems in the CeA and BLA do not regulate the anxiolytic properties of ethanol in this test.

The effects of chronic treadmill and wheel running on behavior in rats.

In order to better understand the behavioral adaptations induced by physical activity, this set of experiments assessed the effects of two modes of running exercise on a battery of behavioral tests. The effects of 8 weeks of forced treadmill running and voluntary wheel running on behavior measures in the elevated plus maze, open field, social interaction and conditioned freezing paradigms were investigated. Eight weeks of treadmill running did not alter behavior in any test paradigm. Rats given unrestricted access to running wheels (WR) had a lower percent open arm time (6.0+/-2.3%) compared to locked wheel controls (LC) (20.7+/-5.7%) in the elevated plus maze. WR also showed decreased entries into center (0.2+/-0.2) and crossed fewer lines (61.0+/-14.9) in the open field compared to control groups. Both WR and LC groups showed increased social interaction; however, these differences are attributed to housing conditions. The effects of 4 weeks of wheel running on elevated plus maze and open field behavior were also investigated to address the possibility of a temporal effect of exercise on behavior. Four weeks of wheel running produced behavioral changes in the open field similar to those found at 8 weeks, but not in the elevated plus maze suggesting a temporal effect of wheel running on plus maze behavior. The behavioral adaptations found after 4 and 8 weeks of wheel running were not due solely to enriched environment and appear to be indicative of enhanced defensive behavior.