Bar press durations as a reliable and robust measure of frustration-related operant behavior: Sensitivity to incentive downshift and dose-response paradigms

In humans, frustrating experiences are known to trigger relapse events and individuals with higher frustration intolerance show increased risk of developing substance use disorders (SUDs). Despite this clear relationship, frustration-related behavior is seldom studied concurrently with self-administration behavior in rodent models. A major obstacle has been the lack of robust, quantitative assays of frustration-related operant behavior thus far. In previous work, we identified increased bar press (BP) durations in response to frustrating conditions in rats self-administering natural or drug rewards. Here, to propose BP durations as a measure of frustration-related behavior, we conducted an operant successive negative contrast (oSNC) study and found that increases in BP durations are observed in the absence of increased effort, providing evidence that this is a psychological phenomenon. Moreover, we assess the viability of widespread use of BP duration measurements as a behavioral tool by quantifying performance as it pertains to sensitivity, robustness, replicability, and sex differences. We conclude that increases in BP durations are a highly sensitive psychological response to frustrating conditions and that this measure is robust, replicable, and applicable to both sexes.

TNFR1 signaling converging on FGF14 controls neuronal hyperactivity and sickness behavior in experimental cerebral malaria

BACKGROUND

Excess tumor necrosis factor (TNF) is implicated in the pathogenesis of hyperinflammatory experimental cerebral malaria (eCM), including gliosis, increased levels of fibrin(ogen) in the brain, behavioral changes, and mortality. However, the role of TNF in eCM within the brain parenchyma, particularly directly on neurons, remains underdefined. Here, we investigate electrophysiological consequences of eCM on neuronal excitability and cell signaling mechanisms that contribute to observed phenotypes.

METHODS

The split-luciferase complementation assay (LCA) was used to investigate cell signaling mechanisms downstream of tumor necrosis factor receptor 1 (TNFR1) that could contribute to changes in neuronal excitability in eCM. Whole-cell patch-clamp electrophysiology was performed in brain slices from eCM mice to elucidate consequences of infection on CA1 pyramidal neuron excitability and cell signaling mechanisms that contribute to observed phenotypes. Involvement of identified signaling molecules in mediating behavioral changes and sickness behavior observed in eCM were investigated in vivo using genetic silencing.

RESULTS

Exploring signaling mechanisms that underlie TNF-induced effects on neuronal excitability, we found that the complex assembly of fibroblast growth factor 14 (FGF14) and the voltage-gated Na+ (Nav) channel 1.6 (Nav1.6) is increased upon tumor necrosis factor receptor 1 (TNFR1) stimulation via Janus Kinase 2 (JAK2). On account of the dependency of hyperinflammatory experimental cerebral malaria (eCM) on TNF, we performed patch-clamp studies in slices from eCM mice and showed that Plasmodium chabaudi infection augments Nav1.6 channel conductance of CA1 pyramidal neurons through the TNFR1-JAK2-FGF14-Nav1.6 signaling network, which leads to hyperexcitability. Hyperexcitability of CA1 pyramidal neurons caused by infection was mitigated via an anti-TNF antibody and genetic silencing of FGF14 in CA1. Furthermore, knockdown of FGF14 in CA1 reduced sickness behavior caused by infection.

CONCLUSIONS

FGF14 may represent a therapeutic target for mitigating consequences of TNF-mediated neuroinflammation.

Fibroblast growth factor 13-mediated regulation of medium spiny neuron excitability and cocaine self-administration

Cocaine use disorder (CUD) is a prevalent neuropsychiatric disorder with few existing treatments. Thus, there is an unmet need for the identification of new pharmacological targets for CUD. Previous studies using environmental enrichment versus isolation paradigms have found that the latter induces increased cocaine self-administration with correlative increases in the excitability of medium spiny neurons (MSN) of the nucleus accumbens shell (NAcSh). Expanding upon these findings, we sought in the present investigation to elucidate molecular determinants of these phenomena. To that end, we first employed a secondary transcriptomic analysis and found that cocaine self-administration differentially regulates mRNA for fibroblast growth factor 13 (FGF13), which codes for a prominent auxiliary protein of the voltage-gated Na+ (Nav) channel, in the NAcSh of environmentally enriched rats (i.e., resilient behavioral phenotype) compared to environmentally isolated rats (susceptible phenotype). Based upon this finding, we used in vivo genetic silencing to study the causal functional and behavioral consequences of knocking down FGF13 in the NAcSh. Functional studies revealed that knockdown of FGF13 in the NAcSh augmented excitability of MSNs by increasing the activity of Nav channels. These electrophysiological changes were concomitant with a decrease in cocaine demand elasticity (i.e., susceptible phenotype). Taken together, these data support FGF13 as being protective against cocaine self-administration, which positions it well as a pharmacological target for CUD.

Improving Environmental Health in Schools

School environmental conditions have immediate and long-term effects on student health and learning. Relying on disconnected, inconsistent, voluntary, or unenforced environmental standards has not resulted in sufficient protection of students from toxic insults. Furthermore, the United States public school system was not prepared to navigate a potentially deadly infectious disease like COVID-19. Although Department of Education agencies have policies to establish clean and safe learning spaces, deficiencies are evident. This article highlights common environmental challenges in schools and opportunities for improvement. Voluntary adoption of rigorous environmental policies by grassroots efforts alone is unlikely to occur in all school systems. In the absence of a legally enforced requirement, the dedication of sufficient resources to update infrastructure and build the environmental health workforce capacity is equally unlikely to occur. Environmental health standards in schools should not be voluntary. Science-based standards should be comprehensive, and part of an actionable, integrated strategy that includes preventive measures and addresses environmental health issues sustainably. Establishing an Integrated Environmental Management approach for schools will require a coordinated capacity-building effort, community-based implementation efforts, and enforcement of minimal standards. Schools will need ongoing technical support and training for staff, faculty, and teachers sufficient to enable them to assume greater oversight and responsibility for environmental management of their schools. Ideally, a holistic approach will include all environmental health components, including IAQ, IPM, green cleaning, pesticide and chemical safety, food safety, fire prevention, building legacy pollutant management, and drinking water quality. Thus, creating a comprehensive management system with continuous monitoring and maintenance. Clinicians who care for children can serve as advocates for children's health beyond their clinic walls by advising parents and guardians to be aware of school conditions and management practices. Medical professionals have always been valued and influential members of communities and school boards. In these roles they can greatly assist in identifying and providing solutions to reduce environmental hazards in schools.

The safeguarding of Chinese traditional martial arts in the past three decades (1990-2020): a perspective of intangible cultural heritage

<p>Traditional martial art is a pivotal part of Chinese folk culture. However, due to the impact of modern culture, the inheritance of various martial arts is threatened. Therefore, many efforts have been made by the Chinese government to protect this unique culture in the late 20^th century. To provide practical indications for the safeguard of intangible cultural heritage, we conducted a literature review for the Chinese strategies concerning the safeguard of traditional martial arts (TMA) in the past 30 years, also tried to identify the advantages and shortcomings of current safeguard of TMA. Existing evidence indicates that the legislative safeguarding of Chinese TMA has gradually evolved into a system for preservation. Modern devices are important to maintain the current form of the intangible cultural heritage. Inviting inheritors of the TMA to teach relevant skills and knowledge in university campuses may play an important role in the dynamic safeguard of inheritance. On the other hand, shortcomings are also noticed. For instance, younger generations are not fully aware of the importance of TMA, thus specific education is needed. The means of transmission of TMA is still insufficient in the current information era.</p>

Lever-press duration as a measure of frustration in sucrose and drug reinforcement

RATIONALE

Currently there is little research into the role of frustration in substance use disorders despite research showing that frustration tolerance in humans is associated with a lower likelihood of developing substance use problems, better outcomes in recovery, and fewer relapses.

OBJECTIVE

In order to address this need, our studies use a rat model to focus on frustration-related behavior in natural reward and addiction-related behavioral procedures. Frustration is defined as when a subject is unable to achieve a reinforcer, receives less of a reinforcer than anticipated, or has to work harder to achieve a reinforcer.

RESULTS

In these studies, bar-press durations increase when rats are in a state of frustration during self-administration of sucrose, fentanyl, or cocaine.

CONCLUSIONS

These data also show that average bar-press durations do not correlate with the number of bar presses, meaning that press duration is an independent measurement that represents a behavioral construct distinct from craving, which is typically measured with number of bar presses. Essentially, these results support that bar press durations can be used as a real-time measure of frustration as a 4th major facet of addiction-related behavior, adding to craving, impulsivity, and habit.

Topographic transcriptomics of the nucleus accumbens shell: Identification and validation of fatty acid binding protein 5 as target for cocaine addiction

Substance use disorders for cocaine are major public health concerns with few effective treatment options. Therefore, identification of novel pharmacotherapeutic targets is critical for future therapeutic development. Evolution has ensured that genes are expressed largely only where they are needed. Therefore, examining the gene expression landscape of the nucleus accumbens shell (NAcSh), a brain region important for reward related behaviors, may lead to the identification of novel targets for cocaine use disorder. In this study, we conducted a novel two-step topographic transcriptomic analysis using five seed transcripts with enhanced expression in the NAcSh to identify transcripts with similarly enhanced expression utilizing the correlation feature to search the more than 20,000 in situ hybridization experiments of the Allen Mouse Brain Atlas. Transcripts that correlated with at least three seed transcripts were analyzed with Ingenuity Pathway Analysis (IPA). We identified 7-fold more NAcSh-enhanced transcripts than our previous analysis using single voxels in the NAcSh as the seed. Analysis of the resulting transcripts with IPA identified many previously identified signaling pathways such as retinoic acid signaling as well as novel pathways. Manipulation of the retinoic acid pathway specifically in the NAcSh of male rats via viral vector-mediated RNA interference targeting fatty acid binding protein 5 (FABP5) decreased cocaine self-administration and modulates excitability of medium spiny neurons in the NAcSh. These results not only validate the prospective strategy of conducting a topographic transcriptomic analysis, but also further validate retinoic acid signaling as a promising pathway for pharmacotherapeutic development against cocaine use disorder.

Opposite regulation of conditioned place preference and intravenous drug self-administration in rodent models: Motivational and non-motivational examples

Although developed from a common antecedent, conditioned place preference (CPP) and intravenous drug self-administration (SA) represent different behavioral paradigms, each with strong face validity. The field has treated results from these studies largely interchangeably; however, there is considerable evidence of opposite modulation of CPP vs. SA. This review outlines four manipulations that differentially affect CPP and SA based on alterations of motivation. These examples are contrasted with one example of differential CPP and SA results that can be explained by simple parallel shifts in dose-response functions. The final two examples have yet to be classified as motivation-based or parallel shifts. Important aspects, including motivation, volitional control of drug administration, reward, and the role of cues are discussed. One major conclusion of this paper is that explanations for apparent discrepancies between CPP and SA require full dose effect functions and assessment of PR breakpoints. Overall, this manuscript offers a more nuanced insight into how CPP and SA can be used to study different aspects of substance use disorders.

Manipulation of retinoic acid signaling in the nucleus accumbens shell alters rat emotional behavior

Novel targets for depression and anxiety disorders are necessary for the development of more effective pharmacotherapeutics. Our previous study found that the retinoic acid (RA) signaling pathway is the signaling pathway most enhanced in the nucleus accumbens (NAc) shell, a region important for depression, anxiety, and addiction. Genetic manipulations of RA signaling in the NAc affecting addiction-related behavior prompted our study of the role of retinoic acid signaling in depression-related and anxiety-related behavior using in vivo RNA interference. Knockdown of the retinoic acid degradation enzyme cytochrome p450 family 26 subfamily b member 1 (Cyp26b1) in the nucleus accumbens shell increased depression-related behavior while decreasing anxiety-like behavior. Knockdown of the retinoic acid binding protein, cellular RA binding protein 2 (Crabp2), also increased depression-related behavior. Knockdown of another RA binding partner fatty acid binding protein 5 (Fabp5), did not alter these behaviors. These results further support the contention that RA signaling in the NAc shell can affect emotional behavior and that targeting some components of this pathway could be a promising avenue for developing novel treatments for depression and anxiety.

Qualitative and quantitative methods in the study of martial arts and combat sports: a panel based on personal experiences

In this panel, five experts present their personal experiences in martial arts and combat sports (MA&CS) research. These experiences represent the two classic approaches to our studies: the quantitative and the qualitative. Above all, the panel aims to foster debate and reflection on the complementarity of these methods when trying to embrace the complexity of MA&CS.

“Deep Cover”: Identities and ethics in martial arts fieldwork

<div><p>Qualitative research in the social sciences typically requires a personal engagement with resource persons. The widely used participant-observation method requires that the researcher assume as far as possible the role of community member. Even when participant observation is not the chosen method, group members assign identities to investigators. Role assignment in martial contexts may range from the “intruder” who disrupts ongoing events (e.g., outsiders may not see “secret techniques”) to one who is allowed insider access, usually after having gone through some test or rite of passage. Data collected in “natural context” is ideal. The primary problem here is that act of observation inevitably changes phenomena under examination. The most effective means of gathering information in a natural context is by engaging in what is known in the Intelligence community as “deep cover” actually joining a community for the purpose of secretly gathering information. This, of course, brings with it serious ethical dilemmas. While it is clear that we must all address the issue of transparency vs. efficiency, most decisions actually are made on a case by case basis. I suggest that it may be time to develop a general set of guidelines to help us keep faith with informants and accomplish our academic goals of accurately depicting the martial cultures with which we engage.</p></div>

Assessing the role of toll-like receptor in isolated, standard and enriched housing conditions

Depression is a common psychiatric disorder that has been poorly understood. Consequently, current antidepressant agents have clinical limitations. Until today, most have exhibited the slow onset of therapeutic action and, more importantly, their effect on remission has been minimal. Thus, the need to find new forms of therapeutic intervention is urgent. The inflammation hypothesis of depression is widely acknowledged and is one that theories the relationship between the function of the immune system and its contribution to the neurobiology of depression. In this research, we utilized an environmental isolation (EI) approach as a valid animal model of depression, employing biochemical, molecular, and behavioral studies. The aim was to investigate the anti-inflammatory effect of etanercept, a tumor necrosis factor-α inhibitor on a toll-like receptor 7 (TLR 7) signaling pathway in a depressive rat model, and compare these actions to fluoxetine, a standard antidepressant agent. The behavioral analysis indicates that depression-related symptoms are reduced after acute administration of fluoxetine and, to a lesser extent, etanercept, and are prevented by enriched environment (EE) housing conditions. Experimental studies were conducted by evaluating immobility time in the force swim test and pleasant feeling in the sucrose preference test. The mRNA expression of the TLR 7 pathway in the hippocampus showed that TLR 7, MYD88, and TRAF6 were elevated in isolated rats compared to the standard group, and that acute treatment with an antidepressant and anti-inflammatory drugs reversed these effects. This research indicates that stressful events have an impact on behavioral well-being, TLR7 gene expression, and the TLR7 pathway. We also found that peripheral administration of etanercept reduces depressive-like behaviour in isolated rats: this could be due to the indirect modulation of the TLR7 pathway and other TLRs in the brain. Furthermore, fluoxetine treatment reversed depressive-like behaviour and molecularly modulated the expression of TLR7, suggesting that fluoxetine exerts antidepressant effects partially by modulating the TLR7 signaling pathway.

Environmental Enrichment and Social Isolation Mediate Neuroplasticity of Medium Spiny Neurons through the GSK3 Pathway

Resilience and vulnerability to neuropsychiatric disorders are linked to molecular changes underlying excitability that are still poorly understood. Here, we identify glycogen-synthase kinase 3β (GSK3β) and voltage-gated Na+ channel Nav1.6 as regulators of neuroplasticity induced by environmentally enriched (EC) or isolated (IC) conditions-models for resilience and vulnerability. Transcriptomic studies in the nucleus accumbens from EC and IC rats predicted low levels of GSK3β and SCN8A mRNA as a protective phenotype associated with reduced excitability in medium spiny neurons (MSNs). In vivo genetic manipulations demonstrate that GSK3β and Nav1.6 are molecular determinants of MSN excitability and that silencing of GSK3β prevents maladaptive plasticity of IC MSNs. In vitro studies reveal direct interaction of GSK3β with Nav1.6 and phosphorylation at Nav1.6T1936 by GSK3β. A GSK3β-Nav1.6T1936 competing peptide reduces MSNs excitability in IC, but not EC rats. These results identify GSK3β regulation of Nav1.6 as a biosignature of MSNs maladaptive plasticity.

Consequences of acute Nav1.1 exposure to deltamethrin

BACKGROUND

Pyrethroid insecticides are the most popular class of insecticides in the world, despite their near-ubiquity, their effects of delaying the onset of inactivation of voltage-gated sodium (Nav) channels have not been well-evaluated in all the mammalian Nav isoforms.

OBJECTIVE

Here we compare the well-studied Nav1.6 isoforms to the less-understood Nav1.1 in their responses to acute deltamethrin exposure.

METHODS

We used patch-clamp electrophysiology to record sodium currents encoded by either Nav1.1 or Nav1.6 channels stably expressed in HEK293 cells. Protocols evaluating both resting and use-dependent modification were employed.

RESULTS

We found that exposure of both isoforms to 10μM deltamethrin significantly potentiated persistent and tail current densities without affecting peak transient current densities, and only Nav1.1 maintained these significant effects at 1μM deltamethrin. Window currents increased for both as well, and while only Nav1.6 displayed changes in activation slope and V1/2 of steady-state inactivation for peak currents, V1/2 of persistent current activation was hyperpolarized of ∼10mV by deltamethrin in Nav1.1 cells. Evaluating use-dependence, we found that deltamethrin again potentiated persistent and tail current densities in both isoforms, but only Nav1.6 demonstrated use-dependent enhancement, indicating the primary deltamethrin-induced effects on Nav1.1 channels are not use-dependent.

CONCLUSION

Collectively, these data provide evidence that Nav1.1 is indeed vulnerable to deltamethrin modification at lower concentrations than Nav1.6, and this effect is primarily mediated during the resting state.

GENERAL SIGNIFICANCE

These findings identify Nav1.1 as a novel target of pyrethroid exposure, which has major implications for the etiology of neuropsychiatric disorders associated with loss of Nav1.1-expressing inhibitory neurons.

Glycogen synthase kinase 3 beta alters anxiety-, depression-, and addiction-related behaviors and neuronal activity in the nucleus accumbens shell

Psychiatric disorders such as anxiety, depression and addiction are often comorbid brain pathologies thought to share common mechanistic biology. As part of the cortico-limbic circuit, the nucleus accumbens shell (NAcSh) plays a fundamental role in integrating information in the circuit, such that modulation of NAcSh circuitry alters anxiety, depression, and addiction-related behaviors. Intracellular kinase cascades in the NAcSh have proven important mediators of behavior. To investigate glycogen-synthase kinase 3 (GSK3) beta signaling in the NAcSh in vivo we knocked down GSK3beta expression with a novel adeno-associated viral vector (AAV2) and assessed changes in anxiety- and depression-like behavior and cocaine self-administration in GSK3beta knockdown rats. GSK3beta knockdown reduced anxiety-like behavior while increasing depression-like behavior and cocaine self-administration. Correlative electrophysiological recordings in acute brain slices were used to assess the effect of AAV-shGSK3beta on spontaneous firing and intrinsic excitability of tonically active interneurons (TANs), cells required for input and output signal integration in the NAcSh and for processing reward-related behaviors. Loose-patch recordings showed that TANs transduced by AAV-shGSK3beta exhibited reduction in tonic firing and increased spike half width. When assessed by whole-cell patch clamp recordings these changes were mirrored by reduction in action potential firing and accompanied by decreased hyperpolarization-induced depolarizing sag potentials, increased action potential current threshold, and decreased maximum rise time. These results suggest that silencing of GSK3beta in the NAcSh increases depression- and addiction-related behavior, possibly by decreasing intrinsic excitability of TANs. However, this study does not rule out contributions from other neuronal sub-types.

Transcriptomics of Environmental Enrichment Reveals a Role for Retinoic Acid Signaling in Addiction

There exists much variability in susceptibility/resilience to addiction in humans. The environmental enrichment paradigm is a rat model of resilience to addiction-like behavior, and understanding the molecular mechanisms underlying this protective phenotype may lead to novel targets for pharmacotherapeutics to treat cocaine addiction. We investigated the differential regulation of transcript levels using RNA sequencing of the rat nucleus accumbens after environmental enrichment/isolation and cocaine/saline self-administration. Ingenuity Pathways Analysis and Gene Set Enrichment Analysis of 14,309 transcripts demonstrated that many biofunctions and pathways were differentially regulated. New functional pathways were also identified for cocaine modulation (e.g., Rho GTPase signaling) and environmental enrichment (e.g., signaling of EIF2, mTOR, ephrin). However, one novel pathway stood out above the others, the retinoic acid (RA) signaling pathway. The RA signaling pathway was identified as one likely mediator of the protective enrichment addiction phenotype, an interesting result given that nine RA signaling-related genes are expressed selectively and at high levels in the nucleus accumbens shell (NAcSh). Subsequent knockdown of Cyp26b1 (an RA degradation enzyme) in the NAcSh of rats confirmed this role by increasing cocaine self-administration as well as cocaine seeking. These results provide a comprehensive account of enrichment effects on the transcriptome and identify RA signaling as a contributing factor for cocaine addiction.

Convergent transcriptomics and proteomics of environmental enrichment and cocaine identifies novel therapeutic strategies for addiction

Transcriptomic and proteomic approaches have separately proven effective at identifying novel mechanisms affecting addiction-related behavior; however, it is difficult to prioritize the many promising leads from each approach. A convergent secondary analysis of proteomic and transcriptomic results can glean additional information to help prioritize promising leads. The current study is a secondary analysis of the convergence of recently published separate transcriptomic and proteomic analyses of nucleus accumbens (NAc) tissue from rats subjected to environmental enrichment vs. isolation and cocaine self-administration vs. saline. Multiple bioinformatics approaches (e.g. Gene Ontology (GO) analysis, Ingenuity Pathway Analysis (IPA), and Gene Set Enrichment Analysis (GSEA)) were used to interrogate these rich data sets. Although there was little correspondence between mRNA vs. protein at the individual target level, good correspondence was found at the level of gene/protein sets, particularly for the environmental enrichment manipulation. These data identify gene sets where there is a positive relationship between changes in mRNA and protein (e.g. glycolysis, ATP synthesis, translation elongation factor activity, etc.) and gene sets where there is an inverse relationship (e.g. ribosomes, Rho GTPase signaling, protein ubiquitination, etc.). Overall environmental enrichment produced better correspondence than cocaine self-administration. The individual targets contributing to mRNA and protein effects were largely not overlapping. As a whole, these results confirm that robust transcriptomic and proteomic data sets can provide similar results at the gene/protein set level even when there is little correspondence at the individual target level and little overlap in the targets contributing to the effects.

Inoculation stress hypothesis of environmental enrichment

One hallmark of psychiatric conditions is the vast continuum of individual differences in susceptibility vs. resilience resulting from the interaction of genetic and environmental factors. The environmental enrichment paradigm is an animal model that is useful for studying a range of psychiatric conditions, including protective phenotypes in addiction and depression models. The major question is how environmental enrichment, a non-drug and non-surgical manipulation, can produce such robust individual differences in such a wide range of behaviors. This paper draws from a variety of published sources to outline a coherent hypothesis of inoculation stress as a factor producing the protective enrichment phenotypes. The basic tenet suggests that chronic mild stress from living in a complex environment and interacting non-aggressively with conspecifics can inoculate enriched rats against subsequent stressors and/or drugs of abuse. This paper reviews the enrichment phenotypes, mulls the fundamental nature of environmental enrichment vs. isolation, discusses the most appropriate control for environmental enrichment, and challenges the idea that cortisol/corticosterone equals stress. The intent of the inoculation stress hypothesis of environmental enrichment is to provide a scaffold with which to build testable hypotheses for the elucidation of the molecular mechanisms underlying these protective phenotypes and thus provide new therapeutic targets to treat psychiatric/neurological conditions.

The Nav1.2 channel is regulated by GSK3

BACKGROUND

Phosphorylation plays an essential role in regulating voltage-gated sodium (Na(v)) channels and excitability. Yet, a surprisingly limited number of kinases have been identified as regulators of Na(v) channels. We posited that glycogen synthase kinase 3 (GSK3), a critical kinase found associated with numerous brain disorders, might directly regulate neuronal Na(v) channels.

METHODS

We used patch-clamp electrophysiology to record sodium currents from Na(v)1.2 channels stably expressed in HEK-293 cells. mRNA and protein levels were quantified with RT-PCR, Western blot, or confocal microscopy, and in vitro phosphorylation and mass spectrometry to identify phosphorylated residues.

RESULTS

We found that exposure of cells to GSK3 inhibitor XIII significantly potentiates the peak current density of Na(v)1.2, a phenotype reproduced by silencing GSK3 with siRNA. Contrarily, overexpression of GSK3β suppressed Na(v)1.2-encoded currents. Neither mRNA nor total protein expression was changed upon GSK3 inhibition. Cell surface labeling of CD4-chimeric constructs expressing intracellular domains of the Na(v)1.2 channel indicates that cell surface expression of CD4-Na(v)1.2 C-tail was up-regulated upon pharmacological inhibition of GSK3, resulting in an increase of surface puncta at the plasma membrane. Finally, using in vitro phosphorylation in combination with high resolution mass spectrometry, we further demonstrate that GSK3β phosphorylates T(1966) at the C-terminal tail of Na(v)1.2.

CONCLUSION

These findings provide evidence for a new mechanism by which GSK3 modulates Na(v) channel function via its C-terminal tail.

GENERAL SIGNIFICANCE

These findings provide fundamental knowledge in understanding signaling dysfunction common in several neuropsychiatric disorders.

Treatment of ionized hypercalcemia in 12 cats (2006-2008) using PO-administered alendronate

Background

Long‐term treatment of cats with ionized hypercalcemia using alendronate has not been evaluated.

Hypothesis/Objectives

Alendronate is well tolerated in treatment of ionized hypercalcemia in cats.

Animals

A total of 12 cats with ionized hypercalcemia.

Methods

Prospective study of 12 cats with ionized hypercalcemia of idiopathic origin was identified by telephone and email communication with a convenience sample of consulting veterinarians. Cats were treated with alendronate at a dose of 5–20 mg per feline PO q7d. Serum ionized calcium concentration (iCa) was measured before beginning treatment with alendronate, and after 1, 3, and 6 months of treatment. Alendronate dosage was adjusted according to iCa. Evaluation included physical examination, CBC, biochemistry profile, and diagnostic imaging. The owners and referring veterinarians were questioned about any observed adverse effects. The Wilcoxon matched‐pairs signed rank test was used to compare baseline iCa to iCa at different time periods.

Results

Alendronate treatment resulted in a decrease in iCa in all 12 cats. The median percentage change in iCa was −13.2%, −15.9%, and −18.1% (range, −29.6 to +7.6; −30.5 to −1.9; −45.8 to +1.5%) at the 1, 3, and 6 month time points, respectively. Baseline iCa was significantly different from 1 month (P = .0042), 3 months (P = .0005), and 6 months (P = .0015). No adverse effects were reported for any of the cats.

Conclusions and Clinical Importance

Alendronate was well tolerated and decreased iCa in most cats for the 6‐month period of observation.

Genesis of anxiety, depression, and ongoing abdominal discomfort in ulcerative colitis-like colon inflammation

Psychological disorders are prevalent in patients with inflammatory bowel disease; the underlying mechanisms remain unknown. We tested the hypothesis that ulcerative colitis-like inflammation induced by dextran sodium sulfate (DSS) exacerbates the ongoing spontaneous activity in colon-projecting afferent neurons that induces abdominal discomfort and anxiety, and depressive-like behaviors in rats. In this study, we used the conditioned place preference and standard tests for anxiety- and depression-like behaviors. DSS rats developed anxiety- and depression-like behaviors 10 to 20 days after the start of inflammation. Single-fiber recordings showed an increase in the frequency of spontaneous activity in L6-S1 dorsal root ganglion (DRG) roots. Prolonged desensitization of transient receptor potential vanilloid 1 (TRPV1)-expressing colonic afferents by resiniferatoxin (RTX) suppressed the spontaneous activity, as well as the anxiety- and depressive-like behaviors. Reduction in spontaneous activity in colon afferents by intracolonic administration of lidocaine produced robust conditioned place preference (CPP) in DSS rats, but not in control rats. Patch-clamp studies demonstrated a significant decrease in the resting membrane potential, lower rheobase, and sensitization of colon-projecting L6-S1 DRG neurons to generate trains of action potentials in response to current injection in DSS rats. DSS inflammation upregulated the mRNA levels of transient receptor potential ankyrin 1 and TRPV1 channels and downregulated that of Kv1.1 and Kv1.4 channels. Ulcerative colitis-like inflammation in rats induces anxiety- and depression-like behaviors, as well as ongoing abdominal discomfort by exacerbating the spontaneous activity in the colon-projecting afferent neurons. Alterations in the expression of voltage- and ligand-gated channels are associated with the induction of mood disorders following colon inflammation.

Overexpression of DeltaFosB in nucleus accumbens mimics the protective addiction phenotype, but not the protective depression phenotype of environmental enrichment

Environmental enrichment produces protective addiction and depression phenotypes in rats. ΔFosB is a transcription factor that regulates reward in the brain and is induced by psychological stress as well as drugs of abuse. However, the role played by ΔFosB in the protective phenotypes of environmental enrichment has not been well studied. Here, we demonstrate that ΔFosB is differentially regulated in rats reared in an isolated condition (IC) compared to those in an enriched condition (EC) in response to restraint stress or cocaine. Chronic stress or chronic cocaine treatment each elevates ΔFosB protein levels in the nucleus accumbens (NAc) of IC rats, but not of EC rats due to an already elevated basal accumulation of ΔFosB seen under EC conditions. Viral-mediated overexpression of ΔFosB in the NAc shell of pair-housed rats (i.e., independent of environmental enrichment/isolation) increases operant responding for sucrose when motivated by hunger, but decreases responding in satiated animals. Moreover, ΔFosB overexpression decreases cocaine self-administration, enhances extinction of cocaine seeking, and decreases cocaine-induced reinstatement of intravenous cocaine self-administration; all behavioral findings consistent with the enrichment phenotype. In contrast, however, ΔFosB overexpression did not alter responses of pair-housed rats in several tests of anxiety- and depression-related behavior. Thus, ΔFosB in the NAc the shell mimics the protective addiction phenotype, but not the protective depression phenotype of environmental enrichment.

Environmental enrichment alters protein expression as well as the proteomic response to cocaine in rat nucleus accumbens

Prior research demonstrated that environmental enrichment creates individual differences in behavior leading to a protective addiction phenotype in rats. Understanding the mechanisms underlying this phenotype will guide selection of targets for much-needed novel pharmacotherapeutics. The current study investigates differences in proteome expression in the nucleus accumbens of enriched and isolated rats and the proteomic response to cocaine self-administration using a liquid chromatography mass spectrometry (LCMS) technique to quantify 1917 proteins. Results of complementary Ingenuity Pathways Analyses (IPA) and gene set enrichment analyses (GSEA), both performed using protein quantitative data, demonstrate that cocaine increases vesicular transporters for dopamine and glutamate as well as increasing proteins in the RhoA pathway. Further, cocaine regulates proteins related to ERK, CREB and AKT signaling. Environmental enrichment altered expression of a large number of proteins implicated in a diverse number of neuronal functions (e.g., energy production, mRNA splicing, and ubiquitination), molecular cascades (e.g., protein kinases), psychiatric disorders (e.g., mood disorders), and neurodegenerative diseases (e.g., Huntington's and Alzheimer's diseases). Upregulation of energy metabolism components in EC rats was verified using RNA sequencing. Most of the biological functions and pathways listed above were also identified in the Cocaine X Enrichment interaction analysis, providing clear evidence that enriched and isolated rats respond quite differently to cocaine exposure. The overall impression of the current results is that enriched saline-administering rats have a unique proteomic complement compared to enriched cocaine-administering rats as well as saline and cocaine-taking isolated rats. These results identify possible mechanisms of the protective phenotype and provide fertile soil for developing novel pharmacotherapeutics. Proteomics data are available via ProteomeXchange with identifier PXD000990.

Differential phosphoproteome regulation of nucleus accumbens in environmentally enriched and isolated rats in response to acute stress

Increasing evidence shows that stress contributes to the pathogenesis of major depressive disorder which is a severe neuropsychiatric disorder and influences over 10% of the world's population. Our previous studies revealed that rats reared in an enriched environment display less depression-related behavior compared to rats raised in an isolated environment, which implies that environmental enrichment produces an antidepressant-like behavioral phenotype. However, the molecular mechanisms are not fully understood. Protein phosphorylation rapidly changes signaling pathway function and alters the function of proteins associated with the stress-induced depressive disorder. Thus, in this study, a phosphoproteomic approach was used to uncover differential phosphoprotein regulation in rat nucleus accumbens between isolated (IC) and enriched environmental conditions (EC) under basal conditions, and in response to acute stress. We found 23 phosphoproteins were regulated in EC vs. IC rats under basal conditions; 10 phosphoproteins regulated by stress in IC rats; and 15 regulated by stress in EC rats. Among all significantly regulated phosphoproteins, 11 of them were represented in at least two conditions. The regulated phosphoproteins represent signaling pathway proteins (including ERK2), enzymes, transcriptional regulators, protein translation regulators, transporters, chaperones and cytoskeletal proteins. These findings provide a global view for further understanding the contribution of protein phosphorylation in depression pathogenesis and antidepressant action.

Neuromedin U receptor 2 knockdown in the paraventricular nucleus modifies behavioral responses to obesogenic high-fat food and leads to increased body weight

Neuromedin U (NMU) is a highly conserved neuropeptide which regulates food intake and body weight. Transgenic mice lacking NMU are hyperphagic and obese, making NMU a novel target for understanding and treating obesity. Neuromedin U receptor 2 (NMUR2) is a high-affinity receptor for NMU found in discrete regions of the central nervous system, in particular the paraventricular nucleus of the hypothalamus (PVN), where it may be responsible for mediating the anorectic effects of NMU. We hypothesized that selective knock down of NMUR2 in the PVN of rats would increase their sensitivity to the reinforcing properties of food resulting in increased intake and preference for high-fat obesogenic food. To this end, we used viral-mediated RNAi to selectively knock down NMUR2 gene expression in the PVN. In rats fed a standard chow, NMUR2 knockdown produced no significant effect on food intake or body weight. However, when the same rats were fed a high-fat diet (45% fat), they consumed significantly more food, gained more body weight, and had increased feed efficiency relative to controls. Furthermore, NMUR2 knockdown rats demonstrated significantly greater binge-type food consumption of the high-fat diet and showed a greater preference for higher-fat food. These results demonstrate that NMUR2 signaling in the PVN regulates consumption and preference for high-fat foods without disrupting feeding behavior associated with non-obesogenic standard chow.

The fibroblast growth factor 14·voltage-gated sodium channel complex is a new target of glycogen synthase kinase 3 (GSK3)

The FGF14 protein controls biophysical properties and subcellular distribution of neuronal voltage-gated Na(+) (Nav) channels through direct binding to the channel C terminus. To gain insights into the dynamic regulation of this protein/protein interaction complex, we employed the split luciferase complementation assay to screen a small molecule library of kinase inhibitors against the FGF14·Nav1.6 channel complex and identified inhibitors of GSK3 as hits. Through a combination of a luminescence-based counter-screening, co-immunoprecipitation, patch clamp electrophysiology, and quantitative confocal immunofluorescence, we demonstrate that inhibition of GSK3 reduces the assembly of the FGF14·Nav channel complex, modifies FGF14-dependent regulation of Na(+) currents, and induces dissociation and subcellular redistribution of the native FGF14·Nav channel complex in hippocampal neurons. These results further emphasize the role of FGF14 as a critical component of the Nav channel macromolecular complex, providing evidence for a novel GSK3-dependent signaling pathway that might control excitability through specific protein/protein interactions.

Psychological stress, cocaine and natural reward each induce endoplasmic reticulum stress genes in rat brain

Our prior research has shown that the transcription of endoplasmic reticulum (ER) stress transcription factors activating transcription factor 3 (ATF3) and ATF4 are induced by amphetamine and restraint stress in rat striatum. However, presently the full extent of ER stress responses to psychological stress or cocaine, and which of the three ER stress pathways is activated is unknown. The current study examines transcriptional responses of key ER stress target genes subsequent to psychological stress or cocaine. Rats were subjected to acute or repeated restraint stress or cocaine treatment and mRNA was isolated from dorsal striatum, medial prefrontal cortex and nucleus accumbens brain tissue. ER stress gene mRNA expression was measured using quantitative polymerase chain reaction (PCR) and RNA sequencing. Restraint stress and cocaine-induced transcription of the classic ER stress-induced genes (BIP, CHOP, ATF3 and GADD34) and of two other ER stress components x-box binding protein 1 (XBP1) and ATF6. In addition, rats living in an enriched environment (large group cage with novel toys changed daily) exhibited rapid induction of GADD34 and ATF3 after 30 min of exploring novel toys, suggesting these genes are also involved in normal non-pathological signaling. However, environmental enrichment, a paradigm that produces protective addiction and depression phenotypes in rats, attenuated the rapid induction of ATF3 and GADD34 after restraint stress. These experiments provide a sensitive measure of ER stress and, more importantly, these results offer good evidence of the activation of ER stress mechanisms from psychological stress, cocaine and natural reward. Thus, ER stress genes may be targets for novel therapeutic targets for depression and addiction.

Energy expenditure and bone formation share a common sensitivity to AP-1 transcription in the hypothalamus

The regulation of bone and fat homeostasis and its relationship to energy expenditure has recently been the focus of increased attention because of its potential relevance to osteoporosis, obesity, and diabetes. Although central effectors within the hypothalamus have been shown to contribute to the regulation of both energy balance and bone homeostasis, little is known of the underlying mechanisms, including the possible involvement of transcriptional factors within the hypothalamus. Transgenic mice overexpressing ΔFosB, a splice variant of the AP-1 transcription factor FosB with mixed agonist-antagonistic properties, have increased energy expenditure and bone mass. Because these mice express ΔFosB in bone, fat, and hypothalamus, we sought to determine 1) whether overexpression of ΔFosB within the hypothalamus was sufficient to regulate energy expenditure and whether it would also regulate bone mass, and 2) whether these effects were the result of antagonism to AP-1. Our results show that stereotactic injection of an adeno-associated virus vector to restrict overexpression of ΔFosB to the ventral hypothalamus of wild-type mice induced a profound increase in both energy expenditure and bone formation and bone mass. This effect was phenocopied, at an even stronger level, by overexpression of a dominant-negative DNJunD, a pure AP-1 antagonist. Taken together, these results suggest that downregulation of AP-1 activity in the hypothalamus profoundly increases energy expenditure and bone formation, leading to both a decrease in adipose mass and an increase in bone mass. These findings may have physiological implications because ΔFosB is expressed and regulated in the hypothalamus.

Introducción al boxeo de la flor del ciruelo: historia, cultura y práctica

<em>Meihuaquan</em> (“Plum Blossom Fist [Boxing]”) has traditionally been practiced as vernacular (folk) art practiced among the Han ethnic group residing in the Shandong, Henan and Hebei Provinces of China. Historical documentation dates Plum Blossom Boxing to the seventeenth century. The classic Chinese novel, <em>Shu</em><em>ǐhǔ Zhuàn </em>(<em>Marsh Chronicles</em>) recounts the martial exploits of Shandong’s twelfth century outlaw heroes who may have been Mei Boxers, also. Thus, for perhaps a millennium, the region has been noted for vernacular martial arts and social banditry. The region’s rampant lawlessness promoted highly-developed martial prowess among both lawbreakers and those who were required to protect themselves against the brigands. Cultural, economic, and environmental factors in the region gave rise to heterodox political and religious beliefs that frequently served as a catalyst for martial sects, most notably the “Boxers” who at the turn of the twentieth century, came into conflict with the imperial government. These factors laid the groundwork for the “character traits” of the art while Taoism, the Five Elements theory, and a concept of predictable change shaped Plum Boxing’s strategic and mechanical principles. In the past decade, there have been efforts to globalize this vernacular martial art. Rather than driving Plum Boxing to extinction it is likely that the folk and the “larger than local” will co-exist.

Nicotine increases dopamine clearance in medial prefrontal cortex in rats raised in an enriched environment

Environmental enrichment results in differential behavioral and neurochemical responsiveness to nicotine. The present study investigates dopamine clearance (CL(DA) ) in striatum and medial prefrontal cortex (mPFC) using in vivo voltammetry in rats raised in enriched (EC) or impoverished conditions (IC) and administered nicotine (0.4 mg/kg) or saline. Baseline CL(DA) in striatum or mPFC was not different between EC and IC. Across repeated DA application, striatal CL(DA) increased in saline-control EC and IC. CL(DA) increased in mPFC in saline-control IC; CL(DA) did not change in saline-control EC. Thus, enrichment differentially alters dynamic responses of the dopamine transporter (DAT) to repeated DA application in mPFC, but not in striatum. In EC, nicotine increased mPFC CL(DA) compared to saline-control, but had no effect on CL(DA) in IC; nicotine had no effect in striatum in EC or IC. Compared to respective saline-controls, nicotine increased dihydroxyphenylacetic acid content in striatum and mPFC in EC, but not in IC. Nicotine also had no effect on DA content in striatum or mPFC in EC or IC. Results indicate that enrichment eliminated the dynamic response of mPFC DAT to repeated DA application in saline-control and augmented the nicotine-induced increase in DAT function in mPFC, but not in striatum.

Environmental enrichment produces a behavioral phenotype mediated by low cyclic adenosine monophosphate response element binding (CREB) activity in the nucleus accumbens

BACKGROUND

Previous research has shown that rats reared in an enriched condition (EC) are more sensitive to the acute effects of amphetamine than rats reared in an isolated condition (IC); yet, EC rats self-administer less amphetamine than IC rats. The present study used cocaine to further explore this environmental enrichment behavioral phenotype, as well as the underlying molecular mechanisms involved.

METHODS

Enriched condition and IC rats were studied in a broad battery of behavioral tests, including cocaine conditioned place preference (CPP) and self-administration and several measures of anxiety- and depression-related behavior. The involvement of the transcription factor, cyclic adenosine monophosphate (cAMP) response element binding protein (CREB), in mediating EC versus IC differences was investigated.

RESULTS

Enriched condition rats exhibited less cocaine self-administration, despite showing enhanced cocaine CPP. Enriched condition rats also displayed less depression-like behavior but higher levels of anxiety-like behavior. This behavioral phenotype is consistent with low CREB activity in the nucleus accumbens, a key brain reward region. Indeed, EC rats have less phospho-CREB (the transcriptionally active form of the protein) in the nucleus accumbens than IC rats, and a selective knockdown of CREB in this brain region of normally reared rats, by use of a novel viral vector expressing a short hairpin RNA (shRNA) directed against CREB, reproduced the EC behavioral phenotype.

CONCLUSIONS

These studies identify a potential molecular mechanism for how rearing environment-a nonpharmacological, nonsurgical manipulation-can modify a wide range of complex emotional behaviors.

CREB regulation of nucleus accumbens excitability mediates social isolation-induced behavioral deficits

Here, we characterized behavioral abnormalities induced by prolonged social isolation in adult rodents. Social isolation induced both anxiety- and anhedonia-like symptoms and decreased cAMP response element-binding protein (CREB) activity in the nucleus accumbens shell (NAcSh). All of these abnormalities were reversed by chronic, but not acute, antidepressant treatment. However, although the anxiety phenotype and its reversal by antidepressant treatment were CREB-dependent, the anhedonia-like symptoms were not mediated by CREB in NAcSh. We found that decreased CREB activity in NAcSh correlated with increased expression of certain K(+) channels and reduced electrical excitability of NAcSh neurons, which was sufficient to induce anxiety-like behaviors and was reversed by chronic antidepressant treatment. Together, our results describe a model that distinguishes anxiety- and depression-like behavioral phenotypes, establish a selective role of decreased CREB activity in NAcSh in anxiety-like behavior, and provide a mechanism by which antidepressant treatment alleviates anxiety symptoms after social isolation.

DeltaFosB induction in orbitofrontal cortex potentiates locomotor sensitization despite attenuating the cognitive dysfunction caused by cocaine

The effects of addictive drugs change with repeated use: many individuals become tolerant of their pleasurable effects but also more sensitive to negative sequelae (e.g., anxiety, paranoia, and drug craving). Understanding the mechanisms underlying such tolerance and sensitization may provide valuable insight into the basis of drug dependency and addiction. We have recently shown that chronic cocaine administration reduces the ability of an acute injection of cocaine to affect impulsivity in rats. However, animals become more impulsive during withdrawal from cocaine self-administration. We have also shown that chronic administration of cocaine increases expression of the transcription factor DeltaFosB in the orbitofrontal cortex (OFC). Mimicking this drug-induced elevation in OFC DeltaFosB through viral-mediated gene transfer mimics these behavioural changes: DeltaFosB over-expression in OFC induces tolerance to the effects of an acute cocaine challenge but sensitizes rats to the cognitive sequelae of withdrawal. Here we report novel data demonstrating that increasing DeltaFosB in the OFC also sensitizes animals to the locomotor-stimulant properties of cocaine. Analysis of nucleus accumbens tissue taken from rats over-expressing DeltaFosB in the OFC and treated chronically with saline or cocaine does not provide support for the hypothesis that increasing OFC DeltaFosB potentiates sensitization via the nucleus accumbens. These data suggest that both tolerance and sensitization to cocaine's many effects, although seemingly opposing processes, can be induced in parallel via the same biological mechanism within the same brain region, and that drug-induced changes in gene expression within the OFC play an important role in multiple aspects of addiction.

Increased impulsivity during withdrawal from cocaine self-administration: role for DeltaFosB in the orbitofrontal cortex

Increased impulsivity caused by addictive drugs is believed to contribute to the maintenance of addiction and has been linked to hypofunction within the orbitofrontal cortex (OFC). Recent data indicate that cocaine "self-administration" induces the transcription factor DeltaFosB in the OFC that alters the effects of investigator-administered cocaine on impulsivity. Here, using viral-mediated gene transfer, the effects of overexpressing DeltaFosB within the OFC were assessed on the cognitive sequelae of chronic cocaine self-administration as measured by the 5-choice serial reaction time task (5CSRT). Cognitive testing occurred in the mornings, and self-administration sessions in the evenings, to enable the progressive assessment of repeated volitional drug intake on performance. Animals self-administering cocaine initially made more omissions and premature or impulsive responses on the 5CSRT but quickly developed tolerance to these disruptive effects. However, withdrawal from cocaine dramatically increased premature responding. When access to cocaine was increased, animals overexpressing DeltaFosB failed to regulate their intake as effectively and were more impulsive during withdrawal. In summary, rats develop tolerance to the cognitive disruption caused by cocaine self-administration and show a deficit in impulse control that is unmasked during withdrawal. Our findings suggest that induction of DeltaFosB within the OFC is one mediator of these effects and, thereby, increases vulnerability to addiction.

Molecular adaptations underlying susceptibility and resistance to social defeat in brain reward regions

While stressful life events are an important cause of psychopathology, most individuals exposed to adversity maintain normal psychological functioning. The molecular mechanisms underlying such resilience are poorly understood. Here, we demonstrate that an inbred population of mice subjected to social defeat can be separated into susceptible and unsusceptible subpopulations that differ along several behavioral and physiological domains. By a combination of molecular and electrophysiological techniques, we identify signature adaptations within the mesolimbic dopamine circuit that are uniquely associated with vulnerability or insusceptibility. We show that molecular recapitulations of three prototypical adaptations associated with the unsusceptible phenotype are each sufficient to promote resistant behavior. Our results validate a multidisciplinary approach to examine the neurobiological mechanisms of variations in stress resistance, and illustrate the importance of plasticity within the brain's reward circuits in actively maintaining an emotional homeostasis.

DeltaFosB induction in orbitofrontal cortex mediates tolerance to cocaine-induced cognitive dysfunction

Current cocaine users show little evidence of cognitive impairment and may perform better when using cocaine, yet withdrawal from prolonged cocaine use unmasks dramatic cognitive deficits. It has been suggested that such impairments arise in part through drug-induced dysfunction within the orbitofrontal cortex (OFC), yet the neurobiological mechanisms remain unknown. We observed that chronic cocaine self-administration increased expression of the transcription factor deltaFosB within both medial and orbitofrontal regions of the rat prefrontal cortex. However, the increase in OFC deltaFosB levels was more pronounced after self-administered rather than experimenter-administered cocaine, a pattern that was not observed in other regions. We then used rodent tests of attention and decision making to determine whether deltaFosB within the OFC contributes to drug-induced alterations in cognition. Chronic cocaine treatment produced tolerance to the cognitive impairments caused by acute cocaine. Overexpression of a dominant-negative antagonist of deltaFosB, deltaJunD, in the OFC prevented this behavioral adaptation, whereas locally overexpressing deltaFosB mimicked the effects of chronic cocaine. Gene microarray analyses identified potential molecular mechanisms underlying this behavioral change, including an increase in transcription of metabotropic glutamate receptor subunit 5 and GABA(A) receptors as well as substance P. Identification of deltaFosB in the OFC as a mediator of tolerance to the effects of cocaine on cognition provides fundamentally new insight into the transcriptional modifications associated with addiction.

Repeated Cocaine Experience Facilitates Sucrose-Reinforced Operant Responding in Enriched and Isolated Rats

The purpose of the present experiment was to determine whether repeated cocaine exposure differentially affects sucrose-reinforced operant responding in rats raised in an enriched condition (EC) or an isolated condition (IC). Specifically, the performance of EC and IC rats pressing a lever for sucrose under a high fixed-ratio schedule (FR 30) prior to and after 10 days of exposure to cocaine (15 mg/kg, i.p.) or saline was compared. Regardless of rearing condition, rats repeatedly exposed to cocaine had shorter reacquisition latencies to complete a sucrose-reinforced FR 30 task than saline controls. The results suggest that cocaine exposure may have cross-sensitized both EC and IC rats to the reinforcing effects of sucrose or sucrose-associated cues, thus facilitating reacquisition of operant responding.

Regulation of fosB and DeltafosB mRNA expression: in vivo and in vitro studies

The transcription factor DeltaFosB, a truncated splice isoform of FosB, accumulates in brain after several types of chronic stimulation. This accumulation is thought to be mediated by the unique stability of DeltaFosB compared to all other Fos family proteins. The goal of the present study was to determine if the relative expression of the two fosB isoforms is also regulated at the mRNA level, thereby further contributing to the selective accumulation of DeltaFosB after chronic stimulation. First, unlike the protein, the half-life of DeltafosB mRNA is only slightly longer than that of full-length fosB mRNA both in cultured cells in vitro and in the brain in vivo. Additionally, similar to c-fos, both fosB isoforms are induced abundantly in striatum after acute administration of amphetamine or stress, and partially desensitize after chronic exposures. Surprisingly, the relative ratio of DeltafosB to fosB mRNA increases most significantly after acute, not chronic, stimulation. Finally, overexpression of polypyrimidine tract binding protein (PTB1), which regulates RNA splicing, in cultured cells decreases the relative expression of DeltafosB compared to fosB mRNA. Together, these findings suggest that splicing of fosB pre-mRNA is regulated by the quantity of unspliced transcript available to the splicing machinery. These data provide fundamental information concerning the generation of DeltafosB mRNA, and indicate that the selective accumulation of DeltaFosB protein with chronic stimulation does not involve its preferential generation by RNA splicing.

Induction of inducible cAMP early repressor expression in nucleus accumbens by stress or amphetamine increases behavioral responses to emotional stimuli

Previous research has shown that cAMP response element (CRE)-mediated transcription is activated in the nucleus accumbens, a major brain reward region, by a variety of environmental stimuli and contributes to neuroadaptations to these stimuli. CRE-binding protein (CREB) is the most studied activator of CRE transcription and has been implicated in this brain region as a gating mechanism for behavioral responses to emotional stimuli. Little attention, however, has been given to naturally occurring inhibitors of CRE-mediated transcription, such as the inducible cAMP early repressor (ICER), an inhibitory product of the CRE modulator gene. In the present study, we investigated the extent to which ICER is induced in the nucleus accumbens by two types of environmental stimuli, stress and amphetamine, and characterized how induction of ICER in this region affects complex behavior. We show that stress and amphetamine each induces ICER expression and that overexpression of ICER in the nucleus accumbens, using viral-mediated gene transfer, increases behavioral responses to both rewarding and aversive emotional stimuli. For example, ICER overexpression increases sensitivity to amphetamine-stimulated locomotor activity as well as to natural rewards such as sucrose and social grooming. However, ICER overexpression also increases measures of anxiety in the elevated plus maze and neophobia to novel tastes. Finally, ICER produces an antidepressant-like effect in the forced swim test, further indication of an enhanced active response to stress. These results suggest that ICER is an important mechanism for modulating CRE-mediated transcription in the nucleus accumbens.

Role of cAMP response element-binding protein in the rat locus ceruleus: regulation of neuronal activity and opiate withdrawal behaviors

The transcription factor cAMP response element-binding protein (CREB) is implicated in mediating the actions of chronic morphine in the locus ceruleus (LC), but direct evidence to support such a role is limited. Here, we investigated the influence of CREB on LC neuronal activity and opiate withdrawal behaviors by selectively manipulating CREB activity in the LC using viral vectors encoding genes for CREBGFP (wild-type CREB tagged with green fluorescent protein), caCREBGFP (a constitutively active CREB mutant), dnCREBGFP (a dominant-negative CREB mutant), or GFP alone as a control. Our results show that in vivo overexpression of CREBGFP in the LC significantly aggravated particular morphine withdrawal behaviors, whereas dnCREBGFP expression attenuated these behaviors. At the cellular level, CREBGFP expression in the LC in vivo and in vitro had no significant effect on neuronal firing at baseline but enhanced the excitatory effect of forskolin (an activator of adenylyl cyclase) on these neurons, which suggests that the cAMP signaling pathway in these neurons was sensitized after CREB expression. Moreover, in vitro studies showed that caCREBGFP-expressing LC neurons fired significantly faster and had a more depolarized resting membrane potential compared with GFP-expressing control cells. Conversely, LC neuronal activity was decreased by dnCREBGFP, and the neurons were hyperpolarized by this treatment. Together, these data provide direct evidence that CREB plays an important role in controlling the electrical excitability of LC neurons and that morphine-induced increases in CREB activity contribute to the behavioral and neural adaptations associated with opiate dependence and withdrawal.

Environmental enrichment decreases nicotine-induced hyperactivity in rats

RATIONALE

Previous research has determined that rats reared in an enriched condition (EC) are more sensitive to the effects of acute systemic amphetamine than rats raised in an impoverished condition (IC).

OBJECTIVES

The present experiments examined the effect of environmental enrichment on locomotor activity following repeated injections of nicotine. Experiment 1 assessed differences in locomotor activity in EC and IC rats and experiment 2 assessed differences between EC rats and rats housed in pairs without novel objects or daily handling (social condition; SC) to determine whether enrichment causes changes beyond that of social contact alone.

METHODS

In experiment 1, EC and IC rats were treated with saline, 0.2 mg/kg or 0.8 mg/kg nicotine, and locomotor activity was assessed for 60 min. Nicotine-induced activity was measured every 48 h for a total of eight sessions. All rats were challenged with 0.8 mg/kg nicotine on session 9. In experiment 2, EC and SC rats were treated with saline or 0.2 mg/kg nicotine, and locomotor activity was assessed using the same regimen as in experiment 1.

RESULTS

In experiment 1, EC rats exhibited less sensitivity than IC rats to the psychostimulant effect of nicotine upon both acute and repeated administration. On the nicotine challenge session (session 9), EC rats were again less sensitive to the hyperactive effects of nicotine. In experiment 2, EC rats were also less sensitive than SC rats to nicotine-induced hyperactivity across repeated injections.

CONCLUSIONS

These results suggest that environmental enrichment during development reduces the stimulant effect of nicotine.

Lobeline does not serve as a reinforcer in rats

RATIONALE

Previous results demonstrated that pretreatment with lobeline attenuates d-methamphetamine self-administration in rats.

OBJECTIVE

The present experiments determined if lobeline serves as a reinforcer, if it decreases d-methamphetamine-induced reinstatement of d-methamphetamine self-administration, and if it activates the mesolimbic and nigrostriatal dopamine (DA) pathways in Sprague-Dawley male rats.

METHODS

The ability of intravenous (IV) lobeline (0.015-0.15 mg/kg per infusion) to engender responding and the ability of lobeline (0.015 and 0.05 mg/kg per infusion) to substitute for d-methamphetamine was determined using the self-administration paradigm. Experiments were also performed to determine if lobeline (1.0 and 3.0 mg/kg) reinstates responding for d-methamphetamine or alters the ability of d-methamphetamine (1.0 mg/kg per infusion) to reinstate responding following extinction. The effect of lobeline (3.0 mg/kg) or d-methamphetamine (1.0 and 3.0 mg/kg) on DA and dihydroxyphenylacetic acid (DOPAC) levels in the nucleus accumbens and striatum were also determined.

RESULTS

Lobeline was not self-administered and did not substitute for d-methamphetamine. Also, lobeline did not reinstate responding for d-methamphetamine following extinction nor did it alter d-methamphetamine-induced reinstatement. Furthermore, lobeline did not alter DA or DOPAC levels in the either the nucleus accumbens or striatum.

CONCLUSIONS

Taken together, the present results indicate that lobeline decreases d-methamphetamine self-administration by decreasing reward, not by acting as a substitute reinforcer.

Lobeline attenuates locomotor stimulation induced by repeated nicotine administration in rats

Lobeline inhibits [3H]nicotine binding to rat brain membranes and nicotine-induced [3H]dopamine release from superfused rat striatal slices, indicating that lobeline acts as a nicotinic receptor antagonist. To determine whether lobeline also inhibits the effects of nicotine in vivo, the present study assessed the effect of lobeline pretreatment on nicotine-induced hyperactivity and sensitization. For 12 consecutive days, rats were injected subcutaneously with lobeline (3 mg/kg) or saline, followed 10 min later by nicotine (0.3 mg/kg) or saline injection, and activity was monitored. To determine if lobeline inhibits induction of sensitization to nicotine, 1 or 28 days later, rats were pretreated with saline followed by nicotine or saline. Lobeline attenuated nicotine-induced hyperactivity when both drugs were administered repeatedly. Although an initial injection of lobeline produced hypoactivity, tolerance to this effect developed. Importantly, tolerance did not develop to the lobeline-induced attenuation of nicotine hyperactivity. Lobeline attenuated the induction of sensitization to nicotine 1 day, but not 28 days, after the cessation of lobeline treatment. These results demonstrate that systemic administration of lobeline attenuates the locomotor-activating effects of repeated nicotine injection and the sensitization to nicotine, consistent with lobeline inhibition of nicotinic receptors and/or neurotransmitter transporters.

Locomotor stimulant effects of nornicotine: role of dopamine

Nornicotine (NORNIC) is a tobacco alkaloid and behaviorally active nicotine metabolite in vivo. Previous behavioral research has shown that NORNIC has locomotor stimulant and reinforcing effects in rats similar to that of nicotine. Results from the current study showed that a bilateral lesion of the nucleus accumbens decreased the locomotor stimulant effect of NORNIC across repeated injections. Pretreatment with the dopamine (DA) D1 receptor antagonist SCH23390 did not block the locomotor stimulant effect of NORNIC or the initiation of sensitization following repeated NORNIC administration. The D2 receptor antagonist eticlopride, however, blocked both the stimulant effect and the initiation of sensitization following repeated NORNIC. Additionally, NORNIC was found to increase synthesis and metabolism of DA, with a greater effect in the mesolimbic pathway compared to the nigrostriatal pathway. Taken together, these results suggest that expression of NORNIC-induced locomotor activity is dependent upon ascending dopaminergic mesolimbic projections, providing additional evidence that NORNIC plays a contributory role in tobacco dependence.

Environmental enrichment decreases intravenous amphetamine self-administration in rats: dose-response functions for fixed- and progressive-ratio schedules

RATIONALE

Although environmental enrichment renders rats more sensitive to the neurobehavioral effects of acute amphetamine, a previous study found that enriched rats self-administer less amphetamine than isolated rats at a low unit dose (0.03 mg/kg per infusion). In that study, however, acquisition of self-administration was limited to only two amphetamine unit doses using a fixed ratio (FR) schedule.

OBJECTIVE

The current study defined the full dose-response relationship for amphetamine self-administration under FR1 and progressive ratio (PR) schedules of reinforcement in rats raised in either an enriched condition (EC) or an isolated condition (IC).

METHODS

Rats were raised from 21 to 50 days of age in either an EC or IC environment. Rats were then trained to press a lever for sucrose before implantation of an intravenous jugular catheter. After implantation of the catheter, rats were allowed to acquire stable response patterns under an FR1 or PR schedule of reinforcement before determination of the dose-response function.RESULTS. EC rats self-administered less amphetamine at a low unit dose under both FR1 (0.006 mg/kg per infusion) and PR (0.02 mg/kg per infusion) schedules. However, responding for high unit doses was similar between the two groups.

CONCLUSIONS

This result suggests that environmental enrichment may be a protective factor for reducing amphetamine intake at a low dose.

Dopaminergic mechanism for caffeine-produced cocaine seeking in rats

Systemic administration of caffeine reinstates extinguished cocaine self-administration behavior in rats, but the mechanism mediating this behavioral effect has not been established. The present study examined the role of adenosinergic A2 and dopaminergic mechanisms in caffeine-produced cocaine seeking. Following extinction of cocaine self-administration, experimenter-administered injections of caffeine (1.25-20 mg/kg) and theophylline (1-10 mg/kg) dose-dependently reinstated extinguished cocaine-seeking behavior. Administration of the adenosinergic A2 antagonist, 3,7-dimethyl-1-propargylxanthine (DMPX; 0.546-2.18 microg/kg), failed to produce cocaine seeking. Pretreatment with doses of the adenosine A1/A2 agonist 5'-N-ethylcarboxamidoadenosine (NECA; 0.003-0.03 mg/kg) that were below those that produced marked sedation failed to block reinstatement. These data suggest that methylxanthine-produced cocaine seeking is not due to adenosine A2 receptor antagonism. In contrast, pretreatment with the dopaminergic D1-like antagonist SCH 23390 (0.005-0.02 mg/kg) or the D2-like antagonist eticlopride (0.03-0.3 mg/kg) produced a dose-dependent attenuation of caffeine-produced reinstatement at doses that did not decrease cocaine self-administration. These findings suggest that dopaminergic mechanisms underlie the ability of caffeine to reinstate extinguished cocaine-taking behavior.