ABSTRACT
Introduction: Alcohol use disorder (AUD) is commonly associated with anxiety disorders and enhanced stress-sensitivity; symptoms that can worsen during withdrawal to perpetuate continued alcohol use. Alcohol increases neuroimmune activity in the brain. Our recent evidence indicates that alcohol directly modulates neuroimmune function in the central amygdala (CeA), a key brain region regulating anxiety and alcohol intake, to alter neurotransmitter signaling. We hypothesized that cannabinoids, such as cannabidiol (CBD) and ∆9-tetrahydrocannabinol (THC), which are thought to reduce neuroinflammation and anxiety, may have potential utility to alleviate alcohol withdrawal-induced stress-sensitivity and anxiety-like behaviors via modulation of CeA neuroimmune function. Methods: We tested the effects of CBD and CBD:THC (3:1 ratio) on anxiety-like behaviors and neuroimmune function in the CeA of mice undergoing acute (4-h) and short-term (24-h) withdrawal from chronic intermittent alcohol vapor exposure (CIE). We further examined the impact of CBD and CBD:THC on alcohol withdrawal behaviors in the presence of an additional stressor. Results: We found that CBD and 3:1 CBD:THC increased anxiety-like behaviors at 4-h withdrawal. At 24-h withdrawal, CBD alone reduced anxiety-like behaviors while CBD:THC had mixed effects, showing increased center time indicating reduced anxiety-like behaviors, but increased immobility time that may indicate increased anxiety-like behaviors. These mixed effects may be due to altered metabolism of CBD and THC during alcohol withdrawal. Immunohistochemical analysis showed decreased S100ß and Iba1 cell counts in the CeA at 4-h withdrawal, but not at 24-h withdrawal, with CBD and CBD:THC reversing alcohol withdrawal effects.. Discussion: These results suggest that the use of cannabinoids during alcohol withdrawal may lead to exacerbated anxiety depending on timing of use, which may be related to neuroimmune cell function in the CeA.
ABSTRACT
Genomic stability is critical for cellular function, however, in the central nervous system highly metabolically active differentiated neurons are challenged to maintain their genome over the organismal lifespan without replication. DNA damage in neurons increases with chronological age and accelerates in neurodegenerative disorders, resulting in cellular and systemic dysregulation. Distinct DNA damage response strategies have evolved with a host of polymerases. The Y-family translesion synthesis (TLS) polymerases are well known for bypassing and repairing damaged DNA in dividing cells. However, their expression, dynamics, and role if any, in enduring postmitotic differentiated neurons of the brain are completely unknown. We show through systematic longitudinal studies for the first time that DNA polymerase kappa (POLK), a member of the Y-family polymerases, is highly expressed in neurons. With chronological age, there is a progressive and significant reduction of nuclear POLK with a concomitant accumulation in the cytoplasm that is predictive of brain tissue age. The reduction of nuclear POLK in old brains is congruent with an increase in DNA damage markers. The nuclear POLK colocalizes with damaged sites and DNA repair proteins. The cytoplasmic POLK accumulates with stress granules and endo/lysosomal markers. Nuclear POLK expression is significantly higher in GABAergic interneurons compared to excitatory pyramidal neurons and lowest in non-neurons, possibly reflective of the inherent biological differences such as firing rates and neuronal activity. Interneurons associated with microglia have significantly higher levels of cytoplasmic POLK in old age. Finally, we show that neuronal activity itself can lead to an increase in nuclear POLK levels and a reduction of the cytoplasmic fraction. Our findings open a new avenue in understanding how different classes of postmitotic neurons deploy TLS polymerase(s) to maintain their genomic integrity over time, which will help design strategies for longevity, healthspan, and prevention of neurodegeneration.
ABSTRACT
BACKGROUND: Clinical and preclinical research indicates that gastric weight loss surgeries, such as Roux-en-Y gastric bypass surgery, can induce alcohol use disorder (AUD). While numerous mechanisms have been proposed for these effects, one relatively unexplored potential mechanism is physical damage to the gastric branch of the vagus nerve, which can occur during bypass surgery. Therefore, we hypothesized that direct damage to the gastric branch of the vagus nerve, without altering other aspects of gastric anatomy, could result in increased alcohol intake. METHODS: To test this hypothesis, we compared alcohol intake and preference in multiple models in male Sprague-Dawley rats that received selective gastric branch vagotomy (VX) with rats who underwent sham surgery. Because the vagus nerve regulates hypothalamic-pituitary-adrenal (HPA) axis function, and alterations to HPA function are critical to the escalation of non-dependent alcohol intake, we also tested the hypothesis that gastric VX increases HPA function. RESULTS: We found that VX increases alcohol intake and preference in the every-other-day, two-bottle choice test and increases preference for 1 g/kg alcohol in the conditioned place preference test. The effects were selective for alcohol, as sucrose intake and preference were not altered by VX. We also found that VX increases corticotropin releasing factor (CRF) mRNA in the paraventricular nucleus of the hypothalamus (PVN), increases putative PVN CRF neuronal action potential firing, and increases corticosterone levels. CONCLUSIONS: Overall, these findings suggest that the vagus nerve may play a critical role in regulating HPA axis function via modulation of PVN CRF mRNA expression and putative PVN CRF neuronal activity. Furthermore, disruptions to vagal regulation of HPA axis function may increase alcohol intake and preference.
ABSTRACT
Opioid use and withdrawal evokes behavioral adaptations such as drug seeking and anxiety, though the underlying neurocircuitry changes are unknown. The basolateral amygdala (BLA) regulates these behaviors through principal neuron activation. Excitatory BLA pyramidal neuron activity is controlled by feedforward inhibition provided, in part, by lateral paracapsular (LPC) GABAergic inhibitory neurons, residing along the BLA/external capsule border. LPC neurons express µ-opioid receptors (MORs) and are potential targets of opioids in the etiology of opioid-use disorders and anxiety-like behaviors. Here, we investigated the effects of opioid exposure on LPC neuron activity using immunohistochemical and electrophysiological approaches. We show that LPC neurons, and other nearby BLA GABA and non-GABA neurons, express MORs and δ-opioid receptors. Additionally, DAMGO, a selective MOR agonist, reduced GABA but not glutamate-mediated spontaneous postsynaptic currents in LPC neurons. Furthermore, in LPC neurons, abstinence from repeated morphine-exposure in vivo (10 mg/kg/day, 5 days, 2 days off) decrease the intrinsic membrane excitability, with a ~75% increase in afterhyperpolarization and ~40-50% enhanced adenylyl cyclase-dependent activity in LPC neurons. These data show that MORs in the BLA are a highly sensitive targets for opioid-induced inhibition and that repeated opioid exposure results in impaired LPC neuron excitability.
Subject(s)
Amygdala , Analgesics, Opioid , Rats , Animals , Analgesics, Opioid/pharmacology , Rats, Sprague-Dawley , GABAergic Neurons , Receptors, OpioidABSTRACT
Background: The endocannabinoid (eCB) system plays an important role in homeostatic regulation of anxiety and stress responses; however, the eCB system can be disrupted following traumatic stressors. Additionally, traumatic or chronic stressors that occur during adulthood or early life can cause long-lasting disturbances in the eCB system. These alterations interfere with hypothalamic-pituitary-adrenal axis function and may be involved in lifelong increased fear and anxiety behaviors as well as increased risk for development of post-traumatic stress disorder (PTSD). Methods: This review focuses on the implications of trauma and significant stressors on eCB functionality and neural pathways, both in adolescence and into adulthood, as well as the current state of testing for CBD efficacy in treating pediatric and adult patients suffering from stress-induced eCB dysregulation. Articles were searched via Pubmed and included studies examining eCB modulation of stress-related disorders in both clinical settings and preclinical models. Conclusion: Given the potential for lifelong alterations in eCB signaling that can mediate stress responsiveness, consideration of pharmaceutical or nutraceutical agents that impact eCB targets may improve clinical outcomes in stress-related disorders. However, caution may be warranted in utilization of medicinal cannabinoid products that contain delta-9-tetrahydrocannabinol due to pronounced euphorigenic effects and potential to exacerbate stress-related behaviors. Other cannabinoid products, such as cannabidiol (CBD), have shown promise in reducing stress-related behaviors in pre-clinical models. Overall, pre-clinical evidence supports CBD as a potential treatment for stress or anxiety disorders resulting from previously stressful events, particularly by reducing fearful behavior and promoting extinction of contextual fear memories, which are hallmarks of PTSD. However, very limited clinical research has been conducted examining the potential effectiveness of CBD in this regard and should be examined further.
Subject(s)
Cannabidiol , Cannabinoids , Adult , Adolescent , Humans , Child , Cannabidiol/pharmacology , Cannabidiol/therapeutic use , Hypothalamo-Hypophyseal System , Pituitary-Adrenal System , Anxiety/drug therapy , Cannabinoids/therapeutic use , EndocannabinoidsABSTRACT
Alcohol use disorders (AUDs) are common mental health issues worldwide and can lead to other chronic diseases. Stress is a major factor in the development and continuation of AUDs, and adolescent alcohol exposure can lead to enhanced stress-responsivity and increased risk for AUD development in adulthood. The exact mechanisms behind the interaction between adolescence, stress, and alcohol are not fully understood and require further research. In this regard, the nucleus of the tractus solitarius (NTS) provides dense norepinephrine projections to the extended amygdala, providing a key pathway for stress-related alcohol behaviors. While NTS norepinephrine neurons are known to be alcohol sensitive, whether adolescent alcohol disrupts NTS-norepinephrine neuron development and if this is related to altered stress-sensitivity and alcohol preference in adulthood has not previously been examined. Here, we exposed male and female C57Bl/6J mice to the commonly used adolescent intermittent ethanol (AIE) vapor model during postnatal day 28-42 and examined AIE effects on: 1) tyrosine hydroxylase (TH) mRNA expression in the NTS across various ages (postnatal day 21-90), 2) behavioral responses to acute stress in the light/dark box test in adulthood, 3) NTS TH neuron responses to acute stress and ethanol challenges in adulthood, and 4) ethanol conditioned place preference behavior in adulthood. Overall the findings indicate that AIE alters NTS TH mRNA expression and increases anxiety-like behaviors following acute stress exposure in a sex-dependent manner. These mRNA expression and behavioral changes occur in the absence of AIE-induced changes in NTS TH neuron sensitivity to either acute stress or acute alcohol exposure or changes to ethanol conditioned place preference.
ABSTRACT
Alcohol use disorder (AUD) is a rapidly growing concern in the United States. Current trending escalations of alcohol use are associated with a concurrent rise in alcohol-related end-organ damage, increasing risk for further diseases. Alcohol-related end-organ damage can be driven by autonomic nervous system dysfunction, however studies on alcohol effects on autonomic control of end-organ function are lacking. Alcohol intake has been shown to reduce insulin secretions from the pancreas. Pancreatic insulin release is controlled in part by preganglionic parasympathetic motor neurons residing in the dorsal motor nucleus of the vagus (DMV) that project to the pancreas. How these neurons are affected by alcohol exposure has not been directly examined. Here we investigated the effects of acute ethanol (EtOH) application on DMV pancreatic-projecting neurons with whole-cell patch-clamp electrophysiology. We found that bath application of EtOH (50 mM) for greater than 30 min significantly enhanced the frequency of spontaneous inhibitory post synaptic current (sIPSC) events of DMV pancreatic-projecting neurons suggesting a presynaptic mechanism of EtOH to increase GABAergic transmission. Thirty-minute EtOH application also decreased action potential firing of these neurons. Pretreatment of DMV slices with 20 µM fluoxetine, a selective serotonin reuptake inhibitor, also increased GABAergic transmission and decreased action potential firing of these DMV neurons while occluding any further effects of EtOH application, suggesting a critical role for serotonin in mediating EtOH effects in the DMV. Ultimately, decreased DMV motor output may lead to alterations in pancreatic secretions. Further studies are needed to fully understand EtOH's influence on DMV neurons as well as the consequences of changes in parasympathetic output to the pancreas.
Subject(s)
Ethanol , Serotonin , Ethanol/pharmacology , Fluoxetine/pharmacology , Insulin/pharmacology , Motor Neurons/physiology , Pancreas , Serotonin/pharmacology , Selective Serotonin Reuptake Inhibitors/pharmacology , Vagus NerveABSTRACT
Alcohol use disorder is a highly significant medical condition characterized by an impaired ability to stop or control alcohol use, compulsive alcohol seeking behavior, and withdrawal symptoms in the absence of alcohol. Understanding how alcohol modulates neurocircuitry critical for long term and binge-like alcohol use, such as the central amygdala (CeA), may lead to the development of novel therapeutic strategies to treat alcohol use disorder. In clinical studies, reduction in the volume of the amygdala has been linked with susceptibility to relapse to alcohol use. Preclinical studies have shown the involvement of the CeA in the effects of alcohol use, with lesions of the amygdala showing a reduction in alcohol drinking, and manipulations of cells in the CeA altering alcohol drinking. A great deal of work has shown that acute alcohol, as well as chronic alcohol exposure via intake or dependence models, alters glutamatergic and GABAergic transmission in the CeA. The CeA, however, contains heterogeneous cell populations and distinct subregional differences in neurocircuit architecture which may influence the mechanism by which alcohol modulates CeA function overall. The current review aimed to parse out the differences in alcohol effects on the medial and lateral subregions of the CeA, and what role neuroinflammatory cells and markers, the endocannabinoid system, and the most commonly studied neuropeptide systems play in mediating these effects. A better understanding of alcohol effects on CeA subregional cell type and neurocircuit function may lead to development of more selective pharmacological interventions for alcohol use disorder.
ABSTRACT
Obesity is associated with insulin resistance, glucose intolerance, inflammation, and altered neuronal activity in brain regions controlling metabolic functions including food intake, energy expenditure, and glucose homeostasis, such as the hypothalamus. In this study, we tested the hypothesis that inhibiting inflammation with minocycline could reduce adverse metabolic consequences associated with high-fat diet (HFD)-induced obesity in mice and sought to determine if metabolic improvements were associated with reduced hypothalamic microglia activity. Male C57Bl/6J mice were placed on 60% HFD for 12 weeks, with minocycline (40 mg/kg, p.o.) or normal tap water given during the last 6 weeks of diet. Age-matched mice maintained on control diet were used as an additional comparator group. Metabolic function was assessed during the last week of treatment. Ramified (resting) and non-ramified (active) microglia were quantified in the hypothalamus following immunohistochemical staining of ionized calcium-binding adaptor 1 (Iba-1) and further assessed by RNAseq. In HFD fed mice, minocycline attenuated body mass and adiposity without altering food intake suggesting enhanced energy expenditure. Minocycline also attenuated hyperinsulinemia and improved insulin sensitivity in HFD mice. Increased microglial activation and autophagy gene network changes were observed in the paraventricular nucleus (PVN) of the hypothalamus of HFD mice, which was prevented by minocycline treatment. Contrary to PVN findings, there were no significant effects of either HFD or minocycline on microglia activation in the hypothalamic arcuate nucleus or central amygdala. Together, these findings suggest that minocycline improves HFD-induced weight gain and insulin resistance in part by reducing inflammatory processes in the PVN, a key hypothalamic region regulating metabolic function.
ABSTRACT
Cannabigerol is a cannabinoid compound synthesized by Cannabis sativa, which in its acid form acts as the substrate for both Δ9-tetraydrocannabinol and cannabidiol formation. Given its lack of psychoactive effects, emerging research has focused on cannabigerol as a potential therapeutic for health conditions including algesia, epilepsy, anxiety, and cancer. While cannabigerol can bind to classical cannabinoid receptors, it is also an agonist at α2-adrenoreceptors (α2AR) which, when activated, inhibit presynaptic norepinephrine release. This raises the possibility that cannabigerol could activate α2AR to reduce norepinephrine release to cardiovascular end organs to lower blood pressure. Despite this possibility, there are no reports examining cannabigerol cardiovascular effects. In this study, we tested the hypothesis that acute cannabigerol administration lowers blood pressure. Blood pressure was assessed via radiotelemetry at baseline and following intraperitoneal injection of cannabigerol (3.3 and 10 mg/kg) or vehicle administered in a randomized crossover design in male C57BL/6J mice. Acute cannabigerol significantly lowered mean blood pressure (-28 ± 2 mmHg with 10 mg/kg versus -12 ± 5 mmHg vehicle, respectively; p = 0.018), with no apparent dose responsiveness (-22 ± 2 mmHg with 3.3 mg/kg). The depressor effect of cannabigerol was lower in magnitude than the α2AR agonist guanfacine and was prevented by pretreatment with the α2AR antagonist atipamezole. These findings suggest that acute cannabigerol lowers blood pressure in phenotypically normal mice likely via an α2AR mechanism, which may be an important consideration for therapeutic cannabigerol administration.
ABSTRACT
The neurobiological mechanisms that regulate the development and maintenance of alcohol use disorder (AUD) are complex and involve a wide variety of within and between systems neuroadaptations. While classic reward, preoccupation, and withdrawal neurocircuits have been heavily studied in terms of AUD, viable treatment targets from this established literature have not proven clinically effective as of yet. Therefore, examination of additional neurocircuitries not classically studied in the context of AUD may provide novel therapeutic targets. Recent studies demonstrate that various neuropeptides systems are important modulators of alcohol reward, seeking, and intake behaviors. This includes neurocircuitry within the dorsal vagal complex (DVC), which is involved in the control of the autonomic nervous system, control of intake of natural rewards like food, and acts as a relay of interoceptive sensory information via interactions of numerous gut-brain peptides and neurotransmitter systems with DVC projections to central and peripheral targets. DVC neuron subtypes produce a variety of neuropeptides and transmitters and project to target brain regions critical for reward such as the mesolimbic dopamine system as well as other limbic areas important for the negative reinforcing and aversive properties of alcohol withdrawal such as the extended amygdala. This suggests the DVC may play a role in the modulation of various aspects of AUD. This review summarizes the current literature on neurotransmitters and neuropeptides systems in the DVC (e.g., norepinephrine, glucagon-like peptide 1, neurotensin, cholecystokinin, thyrotropin-releasing hormone), and their potential relevance to alcohol-related behaviors in humans and rodent models for AUD research. A better understanding of the role of the DVC in modulating alcohol related behaviors may lead to the elucidation of novel therapeutic targets for drug development in AUD.
ABSTRACT
The Central Amygdala (CeA) has been heavily implicated in many aspects of alcohol use disorder. Ethanol (EtOH) has been shown to modulate glutamatergic transmission in the lateral subdivision of the CeA, however, the exact mechanism of this modulation is still unclear. EtOH exposure is associated with increased pro-inflammatory cytokines in the CeA, and inhibition of neuroimmune cells (microglia and astrocytes) has previously been shown to reduce EtOH drinking in animal models. Since neuroimmune activation seems to be involved in many of the effects of EtOH, we hypothesized that acute EtOH exposure will increase excitatory glutamatergic transmission in the CeA via modulation of neuroimmune cells. Using ex vivo brain slice whole-cell patch clamp electrophysiology, it was found that a physiologically relevant concentration of EtOH (20 mM) significantly increased presynaptic glutamatergic transmission in the CeA. Pharmacologic and chemogenetic inhibition of astrocyte function significantly reduced the ability of EtOH to modulate CeA glutamatergic transmission with minimal impact of microglia inhibition. This finding prompted additional studies examining whether direct neuroimmune activation through lipopolysaccharide (LPS) might lead to an increase in the glutamatergic transmission in the CeA. It was found that LPS modulation of glutamatergic transmission was limited by microglia activation and required astrocyte signaling. Taken together these results support the hypothesis that acute EtOH enhances lateral CeA glutamatergic transmission through an astrocyte mediated mechanism.
Subject(s)
Astrocytes/drug effects , Central Amygdaloid Nucleus/drug effects , Central Nervous System Depressants/pharmacology , Electrophysiological Phenomena/drug effects , Ethanol/pharmacology , Glutamic Acid/drug effects , Microglia/drug effects , Animals , MiceABSTRACT
Alcohol Use Disorder (AUD) affects around 14.5 million individuals in the United States, with Substance Use Disorder (SUD) affecting an additional 8.3 million individuals. Relapse is a major barrier to effective long-term treatment of this illness with stress often described as a key trigger for a person with AUD or SUD to relapse during a period of abstinence. Two signaling molecules, norepinephrine (NE) and corticotropin releasing factor (CRF), are released during the stress response, and also play important roles in reward behaviors and the addiction process. Within the addiction literature, one brain region in which there has been increasing research focus in recent years is the bed nucleus of the stria terminalis (BNST). The BNST is a limbic structure with numerous cytoarchitecturally and functionally different subregions that has been implicated in drug-seeking behaviors and stress responses. This review focuses on drug and stress-related neurocircuitry changes in the BNST, particularly within the CRF and NE systems, with an emphasis on differences and similarities between the major dorsal and ventral BNST subregions.
Subject(s)
Corticotropin-Releasing Hormone/metabolism , Norepinephrine/metabolism , Septal Nuclei/metabolism , Stress, Psychological/metabolism , Substance-Related Disorders/metabolism , Alcoholism/metabolism , Alcoholism/psychology , Animals , Corticotropin-Releasing Hormone/physiology , Drug-Seeking Behavior , Humans , Mice , Norepinephrine/physiology , Rats , Receptors, Adrenergic/physiology , Stress, Psychological/psychology , Substance-Related Disorders/psychologyABSTRACT
Obesity is a chronic state of energy imbalance that represents a major public health problem and greatly increases the risk for developing hypertension, hyperglycemia, and a multitude of related pathologies that encompass the metabolic syndrome. The underlying mechanisms and optimal treatment strategies for obesity, however, are still not fully understood. The control of energy balance involves the actions of circulating hormones on a widely distributed network of brain regions involved in the regulation of food intake and energy expenditure, including the arcuate nucleus of the hypothalamus. While obesity is known to disrupt neurocircuits controlling energy balance, including those in the hypothalamic arcuate nucleus, the pharmacological targeting of these central mechanisms often produces adverse cardiovascular and other off-target effects. This highlights the critical need to identify new anti-obesity drugs that can activate central neurocircuits to induce weight loss without negatively impacting blood pressure control. The renin-angiotensin system may provide this ideal target, as recent studies show this hormonal system can engage neurocircuits originating in the arcuate nucleus to improve energy balance without elevating blood pressure in animal models. This review will summarize the current knowledge of renin-angiotensin system actions within the arcuate nucleus for control of energy balance, with a focus on emerging roles for angiotensin II, prorenin, and angiotensin-(1-7) pathways.
Subject(s)
Arcuate Nucleus of Hypothalamus/metabolism , Obesity/metabolism , Renin-Angiotensin System , Animals , Eating , Energy Metabolism , HumansABSTRACT
Animal models have significantly contributed to the understanding of reward-related behaviors, such as in Substance Use Disorder research. One of the most heavily utilized paradigms to date is conditioned place preference (CPP). However, CPP is limited by non-contingent exposure. Our new method advances this classic method by utilizing its benefits and simultaneously diminishing its limitations. We used a traditional 3-compartment CPP apparatus, where each chamber differs by both visual and tactile contexts. We restructured the apparatus allowing for insertion of bottles so that mice could orally self-administer sucrose or morphine-containing solutions in a specific context. Our results show that mice who self-administer sucrose or morphine show a place preference for the sucrose- or morphine-paired chamber. This place preference lasts for 21 d in sucrose-treated, but not morphine-treated mice. Additionally, we found that that mice will drink more water in the morphine-paired context during extinction tests. This model combines the distinct contextual cues associated with conditioned place preference and combines them with voluntary self-administration, thus enabling researchers to measure behavior using a model that incorporates spatial memory involved in affective states, while also providing a quantifiable readout of context/environment-specific drug seeking. In conclusion, we combined CPP and voluntary intake to establish a novel technique to assess not only preference for a context associated with rewarding stimuli (natural or drug), but also seeking, retention, and locomotor activity. This model can be further utilized to examine other drugs of abuse, extinction training, other learning models, or to allow for the assessment of neurobiological manipulations.
Subject(s)
Drug-Seeking Behavior , Reward , Animals , Conditioning, Classical , Cues , Mice , Morphine/pharmacologyABSTRACT
Patients suffering from opioid use disorder often relapse during periods of abstinence, which is posited to be caused by negative affective states that drive motivated behaviors. Here, we explored whether conditioning mice with morphine in a conditioned place preference (CPP) training paradigm evoked anxiety-like behavior during morphine abstinence. To do this, mice were conditioned with morphine (10 mg/kg, i.p.) for 5 days. Twenty-four hours following conditioning, anxiety levels were tested by measuring time in the open arms of the elevated plus-maze. The next day, mice were placed in the three-compartment chamber to measure morphine-induced CPP. Our results show that following morphine conditioning, mice spent significantly less time in the open arm of the elevated plus-maze and expressed robust morphine CPP on CPP test day. Furthermore, we found that an acute treatment with (R,S)-ketamine (10 mg/kg, i.p.), a medication demonstrating promise for preventing anxiety-related phenotypes, 30 min before testing on post-conditioning day 1, increased time spent in the open arm of the elevated plus-maze in saline- and morphine-conditioned mice. Additionally, we found that the second injection of ketamine 30 min before CPP tests on post-conditioning day 2 prevented morphine-induced CPP, which lasted for up to 28 days post-conditioning. Furthermore, we found that conditioning mice with 10% (w/v) sucrose using an oral self-administration procedure did not evoke anxiety-like behavior, but elicited robust CPP, which was attenuated by ketamine treatment 30 min before CPP tests. Overall, our results suggest that the ketamine-induced block of morphine CPP may not be attributed solely to alleviating negative affective states, but potentially through impaired memory of morphine-context associations.
ABSTRACT
Alcoholism and high fat diet (HFD)-induced obesity individually promote insulin resistance and glucose intolerance in clinical populations, increasing risk for metabolic diseases. HFD can also stimulate alcohol intake in short-term clinical studies. Unfortunately, there is currently a disconnect between animal models and the clinical findings, as animal studies typically show that HFD decreases ethanol intake while ethanol intake mitigates HFD-induced effects on insulin and glucose dysfunction. However, most previous animal studies utilized forced or continuous HFD and/or ethanol. In three experiments we sought to determine whether HFD (HFD = 60% calories from fat) vs. control diet (chow = 16% fat) alters voluntary two-bottle choice ethanol intake in male C57Bl/6J mice given differing access schedules for 6-7 weeks, and we assessed the resultant impact on metabolic function via insulin and glucose tolerance tests. Experiment 1: Unlimited Access Ethanol + HFD (UAE + HFD; n = 15; 10% ethanol v/v, ad libitum diet and ethanol) or UAE + Chow (n = 15). Experiment 2: Limited Access Ethanol + HFD (LAE + HFD; n = 15; ethanol = 4 h/day; 3 days/week, ad libitum diet) or LAE + Chow (n = 15) with increasing ethanol concentrations (10%, 15%, 20%). Experiment 3: Intermittent HFD with limited access to ethanol (iHFD-E; HFD = single 24-h session/week; ethanol = 4 h/day; 4 days/week) (n = 10). UAE + HFD mice consumed significantly less ethanol and were insulin-resistant and hyperglycemic compared with UAE + Chow mice. LAE + HFD mice consumed ethanol similarly to LAE + Chow mice, but exhibited hyperglycemia, insulin resistance, and glucose intolerance. iHFD-E mice displayed binge eating-like behaviors and consumed significantly more ethanol than mice given ad libitum chow or HFD. iHFD-E mice did not have significantly altered body composition, but developed insulin insensitivity and glucose intolerance. These findings suggest that access schedules influence HFD effects on ethanol consumption and resultant metabolic dysfunction, ethanol intake does not improve HFD-induced metabolic dysfunction, and binge eating-like behaviors can transfer to binge drinking behaviors.
Subject(s)
Alcohol Drinking/metabolism , Diet, High-Fat , Feeding Behavior/physiology , Glucose/metabolism , Insulin/metabolism , Animals , Bulimia/metabolism , Eating , Energy Intake , Ethanol/metabolism , Glucose Tolerance Test , Male , Mice , Mice, Inbred C57BLABSTRACT
The prevalence of psychiatry disorders such as anxiety and depression has steadily increased in recent years in the United States. This increased risk for anxiety and depression is associated with excess weight gain, which is often due to over-consumption of western diets that are typically high in fat, as well as with binge eating disorders, which often overlap with overweight and obesity outcomes. This finding suggests that diet, particularly diets high in fat, may have important consequences on the neurocircuitry regulating emotional processing as well as metabolic functions. Depression and anxiety disorders are also often comorbid with alcohol and substance use disorders. It is well-characterized that many of the neurocircuits that become dysregulated by overconsumption of high fat foods are also involved in drug and alcohol use disorders, suggesting overlapping central dysfunction may be involved. Emerging preclinical data suggest that high fat diets may be an important contributor to increased susceptibility of binge drug and ethanol intake in animal models, suggesting diet could be an important aspect in the etiology of substance use disorders. Neuroinflammation in pivotal brain regions modulating metabolic function, food intake, and binge-like behaviors, such as the hypothalamus, mesolimbic dopamine circuits, and amygdala, may be a critical link between diet, ethanol, metabolic dysfunction, and neuropsychiatric conditions. This brief review will provide an overview of behavioral and physiological changes elicited by both diets high in fat and ethanol consumption, as well as some of their potential effects on neurocircuitry regulating emotional processing and metabolic function.
ABSTRACT
BACKGROUND: Angiotensin-(1-7) is a beneficial hormone of the renin-angiotensin system known to play a positive role in regulation of blood pressure and glucose homeostasis. Previous studies have shown that in high-fat diet (HFD)-induced obese male mice, circulating angiotensin-(1-7) levels are reduced and chronic restoration of this hormone reverses diet-induced insulin resistance; however, this has yet to be examined in female mice. We hypothesized angiotensin-(1-7) would improve insulin sensitivity and glucose tolerance in obese female mice, to a similar extent as previously observed in male mice. METHODS: Five-week-old male and female C57BL/6J mice (8-12/group) were placed on control diet or HFD (16% or 59% kcal from fat, respectively) for 11 weeks. After 8 weeks of diet, mice were implanted with an osmotic pump for 3-week subcutaneous delivery of angiotensin-(1-7) (400 ng/kg/min) or saline vehicle. During the last week of treatment, body mass and composition were measured and intraperitoneal insulin and glucose tolerance tests were performed to assess insulin sensitivity and glucose tolerance, respectively. Mice were euthanized at the end of the study for blood and tissue collection. RESULTS: HFD increased body mass and adiposity in both sexes. Chronic angiotensin-(1-7) infusion significantly decreased body mass and adiposity and increased lean mass in obese mice of both sexes. While both sexes tended to develop mild hyperglycemia in response to HFD, female mice developed less marked hyperinsulinemia. There was no effect of angiotensin-(1-7) on fasting glucose or insulin levels among diet and sex groups. Male and female mice similarly developed insulin resistance and glucose intolerance in response to HFD feeding. Angiotensin-(1-7) improved insulin sensitivity in both sexes but corrected glucose intolerance only in obese female mice. There were no effects of sex or angiotensin-(1-7) treatment on any of the study outcomes in control diet-fed mice. CONCLUSIONS: This study provides new evidence for sex differences in the impact of chronic angiotensin-(1-7) in obese mice, with females having greater changes in glucose tolerance with treatment. These findings improve understanding of sex differences in renin-angiotensin mechanisms in obesity and illustrate the potential for targeting angiotensin-(1-7) for treatment of this condition.