Dopamine receptors in the striatum of rats exposed to repeated restraint stress and alprazolam treatment

Christensenella minuta mitigates behavioral and cardiometabolic hallmarks of social defeat stress

Psychological stress during early development and adolescence may increase the risk of psychiatric and cardiometabolic comorbidities in adulthood. The gut microbiota has been associated with mental health problems such as depression and anxiety and with cardiometabolic disease, but the potential role of the gut microbiota in their comorbidity is not well understood. We investigated the effects and mode of action of the intestinal bacterium Christensenella minuta DSM 32891 on stress-induced mental health and cardiometabolic disturbances in a mouse model of social defeat stress. We demonstrate that administered C. minuta alleviates chronic stress-induced depressive, anxiogenic and antisocial behavior. These effects are attributed to the bacterium's ability to modulate the hypothalamic-pituitary-adrenal axis, which mediates the stress response. This included the oversecretion of corticosterone and the overexpression of its receptors, as well as the metabolism of dopamine (DA) and the expression of its receptors (D1, D2L and D2S). Additionally, C. minuta administration reduced chronically induced inflammation in plasma, spleen and some brain areas, which likely contribute to the recovery of physical and behavioral function. Furthermore, C. minuta administration prevented chronic stress-induced cardiovascular damage by regulating key enzymes mediating liver fibrosis and oxidative stress. Finally, C. minuta increased the abundance of bacteria associated with mental health. Overall, our study highlights the potential of microbiota-directed interventions to alleviate both the physical and mental effects of chronic stress.

Mother's little helper turned a foe: Alprazolam use, misuse, and abuse

Benzodiazepines are effective in managing anxiety and related disorders when used properly (short-term). Their inappropriate use, however, carries significant risks, involving amnesia, rebound insomnia, rebound anxiety, depression, dependence, abuse, addiction, and an intense and exceedingly prolonged withdrawal, among other complications. Benzodiazepines also amplify the effects of opioids and, consequently, have been implicated in approximately 30 % of opioid overdose deaths. Despite their unfavorable profile, sharp increases in medical and non-medical use of benzodiazepines have been steadily reported worldwide. Alprazolam (Xanax®), a potent, short-acting benzodiazepine, is among the most prescribed and abused anxiolytics in the United States. This medication is commonly co-abused with opioids, increasing the likelihood for oversedation, overdose, and death. Notwithstanding these risks, it is surprising that research investigating how benzodiazepines, such as alprazolam, interact with opioids is severely lacking in clinical and preclinical settings. This review therefore aims to present our current knowledge of benzodiazepine use and misuse, with an emphasis on alprazolam when data is available, and particularly in populations at higher risk for developing substance use disorders. Additionally, the potential mechanism(s) surrounding tolerance, dependence and abuse liability are discussed. Despite their popularity, our understanding of how benzodiazepines and opioids interact is less than adequate. Therefore, it is now more important than ever to understand the short- and long-term consequences of benzodiazepine/alprazolam use.

Rasd2 regulates depression-like behaviors via DRD2 neurons in the prelimbic cortex afferent to nucleus accumbens core circuit

Depressive symptoms, such as anhedonia, decreased social interaction, and lack of motivation, implicate brain reward systems in the pathophysiology of depression. Exposure to chronic stress impairs the function of brain reward circuits and is well-known to be involved in the etiology of depression. A transcriptomic analysis found that stress alters the expression of Rasd2 in mice prefrontal cortex (PFC). Similarly, in our previous study, acute fasting decreased Rasd2 expression in mice PFC, and RASD2 modulated dopamine D2 receptor (DRD2)-mediated antidepressant-like effects in ovariectomized mice. This research suggests the role of RASD2 in stress-induced depression and its underlying neural mechanisms that require further investigation. Here, we show that 5-day unpredictable mild stress (5-d UMS) exposure reduces RASD2 expression in both the nucleus accumbens (NAc) and medial prefrontal cortex (mPFC) of mice, while overexpression (but not knock-down) of Rasd2 in the NAc core (NAcc) alleviates 5-d UMS-induced depression-like behaviors and activates the DRD2-cAMP-PKA-DARPP-32 signaling pathway. Further studies investigated neuronal projections between the mPFC (Cg1, PrL, and IL) and NAcc, labeled by the retrograde tracer Fluorogold. Depression-like behaviors induced by 5-d UMS were only related to inhibition of the PrL-NAcc circuit. DREADD (Designer receptors exclusively activated by designer drug) analysis found that the activation of PrL-NAcc glutaminergic projection alleviated depression-like behaviors and increased DRD2- and RASD2-positive neurons in the NAcc. Using Drd2-cre transgenic mice, we constructed mice with Rasd2 overexpression in DRD2PrL-NAcc neurons, finding that Rasd2 overexpression ameliorated 5-d UMS-induced depression-like behaviors. These findings demonstrate a critical role for RASD2 modulation of DRD2PrL-NAcc neurons in 5-d UMS-induced depression-like behaviors. In addition, the study identifies a new potential strategy for precision medical treatment of depression.

Dopaminergic and norepinephrinergic modulation of endogenous event-related potentials: A systematic review and meta-analysis

Event-related potentials (ERPs) represent the cortical processing of sensory, motor or cognitive functions invoked by particular events or stimuli. A current theory posits that the catecholaminergic neurotransmitters dopamine (DA) and norepinephrine (NE) modulate a number of endogenous ERPs during various cognitive processes. This manuscript aims to evaluate a leading neurotransmitter hypothesis with a systematic overview and meta-analysis of pharmacologic DA and NE manipulation of specific ERPs in healthy subjects during executive function. Specifically, the frontally-distributed P3a, N2, and Ne/ERN (or error-related negativity) are supposedly modulated primarily by DA, whereas the parietally-distributed P3b is thought to be modulated by NE. Based on preceding research, we refer to this distinction between frontally-distributed DA-sensitive and parietally-distributed NE-sensitive ERP components as the Extended Neurobiological Polich (ENP) hypothesis. Our systematic review and meta-analysis indicate that this distinction is too simplistic and many factors interact with DA and NE to influence these specific ERPs. These may include genetic factors, the specific cognitive processes engaged, or elements of study design, i.e. session or sequence effects or data-analysis strategies.

Alprazolam modulates persistence energy during emotion processing in first-degree relatives of individuals with schizophrenia: a network control study

Schizophrenia is marked by deficits in facial affect processing associated with abnormalities in GABAergic circuitry, deficits also found in first-degree relatives. Facial affect processing involves a distributed network of brain regions including limbic regions like amygdala and visual processing areas like fusiform cortex. Pharmacological modulation of GABAergic circuitry using benzodiazepines like alprazolam can be useful for studying this facial affect processing network and associated GABAergic abnormalities in schizophrenia. Here, we use pharmacological modulation and computational modeling to study the contribution of GABAergic abnormalities toward emotion processing deficits in schizophrenia. Specifically, we apply principles from network control theory to model persistence energy - the control energy required to maintain brain activation states - during emotion identification and recall tasks, with and without administration of alprazolam, in a sample of first-degree relatives and healthy controls. Here, persistence energy quantifies the magnitude of theoretical external inputs during the task. We find that alprazolam increases persistence energy in relatives but not in controls during threatening face processing, suggesting a compensatory mechanism given the relative absence of behavioral abnormalities in this sample of unaffected relatives. Further, we demonstrate that regions in the fusiform and occipital cortices are important for facilitating state transitions during facial affect processing. Finally, we uncover spatial relationships (i) between regional variation in differential control energy (alprazolam versus placebo) and (ii) both serotonin and dopamine neurotransmitter systems, indicating that alprazolam may exert its effects by altering neuromodulatory systems. Together, these findings provide a new perspective on the distributed emotion processing network and the effect of GABAergic modulation on this network, in addition to identifying an association between schizophrenia risk and abnormal GABAergic effects on persistence energy during threat processing.

BDZs, designer BDZs, and Z-drugs: pharmacology and misuse insights

Benzodiazepines (BZDs) are a widely prescribed class of sedative-hypnotics compounds for the treatment of a broad range of conditions as anxiety and obsessive-compulsive disorders, phobias, sleep related problems associated with insomnia and for the management of alcohol and GHB withdrawal. Zolpidem, zopiclone and zaleplon, commonly known as Z-drugs are non-benzodiazepine hypnotic drug with pharmacology similar to BDZs. Despite their usefulness, BDZs and Z-drugs present a potential for abuse and dependence. Moreover, the non-medical use of BDZs is a well-known phenomenon and represents an increasingly widespread public health problem since is associated with an elevated risk of serious health consequences or fatal overdose, especially among specific group of users. The spectrum of BDZs and Z-drugs misuse is extended by new synthetic BDZs, which may pose high risks to users, since the majority have never undergone clinical trials or tests and consequently their pharmacology and toxicology is largely unknown.

Stress and the dopaminergic reward system

Dopamine regulates reward-related behavior through the mesolimbic dopaminergic pathway. Stress affects dopamine levels and dopaminergic neuronal activity in the mesolimbic dopamine system. Changes in mesolimbic dopaminergic neurotransmission are important for coping with stress, as they allow adaption to behavioral responses to various environmental stimuli. Upon stress exposure, modulation of the dopaminergic reward system is necessary for monitoring and selecting the optimal process for coping with stressful situations. Aversive stressful events may negatively regulate the dopaminergic reward system, perturbing reward sensitivity, which is closely associated with chronic stress-induced depression. The mesolimbic dopamine system is excited not only by reward but also by aversive stressful stimuli, which adds further intriguing complexity to the relationship between stress and the reward system. This review focuses on lines of evidence related to how stress, especially chronic stress, affects the mesolimbic dopamine system, and discusses the role of the dopaminergic reward system in chronic stress-induced depression.

Effects of acupuncture on stress-induced relapse to cocaine-seeking in rats

RATIONALE

Cocaine addiction is associated with high rates of relapse, and stress has been identified as a major risk factor. We have previously demonstrated that acupuncture reduces drug self-administration and dopamine release in the nucleus accumbens (NAc), a brain structure implicated in stress-induced reinstatement of drug-seeking behavior.

OBJECTIVE

This study was conducted to investigate the effects of acupuncture on footshock-induced reinstatement of cocaine-seeking and the expression of c-Fos and the transcription factor cAMP response element-binding protein (CREB) in the NAc, used as markers of neuronal activation in conditions of stress-induced reinstatement to cocaine.

METHODS

Male Sprague-Dawley rats were trained to self-administer cocaine (1.0 mg/kg) for 14 days, followed by extinction and then footshock stress. Acupuncture was applied at bilateral Shenmen (HT7) points for 1 min after footshock stress.

RESULTS AND CONCLUSIONS

Acute footshock stress reinstated cocaine-seeking behavior and enhanced c-Fos expression and phosphorylated CREB (pCREB) activation in the NAc shell in cocaine pre-exposed rats. On the other hand, acupuncture at HT7, but not at control point (LI5), markedly reduced reinstatement of cocaine-seeking (86.5 % inhibition vs. control value), c-Fos expression (81.7% inhibition), and pCREB activation (79.3% inhibition) in the NAc shell. These results suggest that acupuncture attenuates stress-induced relapse by regulating neuronal activation in the NAc shell.

Activating effects of chronic variable stress in rats with different exploratory activity: association with dopamine d(1) receptor function in nucleus accumbens

BACKGROUND/AIMS

Rats display persistent behavioural phenotypes of low (LE) versus high (HE) exploratory activity in the exploration box paradigm. LE rats that prefer passive coping strategies show differential dopaminergic activity in the striatum. The main hypothesis of this study was that chronic variable stress (CVS) would have a higher impact on LE rats.

METHODS

Animals were submitted to a CVS regimen lasting 32 days that was followed by a behavioural test battery. The functional states of their dopamine D(1) and D(2) receptors were measured in the striatum and nucleus accumbens (NAcc). Cerebral oxidative metabolism was assessed via cytochrome c oxidase histochemistry in 65 brain regions.

RESULTS

CVS decreased weight gain, to a higher extent in LE rats, and lowered the sucrose preference after the first week, but habituation to the anhedonic effect had developed by the end of the experiment. CVS did not change the behavioural phenotypes initially assigned. No effect of stress on D(2) receptor function was found. Chronically stressed animals exhibited higher levels of social interaction and D(1) receptor-mediated cAMP accumulation in the NAcc, but not in the striatum. CVS was associated with higher oxidative metabolism levels in the anteroventral thalamus, median raphe nuclei and central periaqueductal grey matter. These changes after stress did not depend upon the exploratory phenotype.

CONCLUSION

This study revealed changes in brain biochemistry after habituation to CVS that might be implicated in successful adaptation to chronic stress.

Differential response of central dopaminergic system in acute and chronic unpredictable stress models in rats

We aimed to evaluate the response of dopaminergic system in acute stress (AS) and chronic unpredictable stress (CUS) by measuring dopamine (DA) levels, its receptor densities in the frontal cortex, striatum, hippocampus, amygdala and orbito-frontal cortex regions of rat brain, and investigated the corresponding behavioral locomotor changes. Involvement of D(1) receptor was also examined during AS and CUS using A 68930, a D(1) selective agonist. Rats were exposed to AS (single immobilization for 150 min) and CUS (two different stressors for 7 days). AS significantly decreased the DA levels in the striatum and hippocampus, and A 68930 pretreatment significantly reverted these changes. However, in the frontal cortex significantly increased DA levels were remain unchanged following A 68930. CUS led to a decrease of DA levels in the frontal cortex, striatum and hippocampus, which were normalized by A 68930. Saturation radioligand binding assays revealed a significant decrease in the number of D(1)-like receptors in the frontal cortex during CUS, which were further decreased by A 68930 pretreatment. However, in the striatum and hippocampus, A 68930 pretreatment reduced the CUS induced increase in the number of D(1)-like receptors. No significant changes were observed in the amygdala and orbito-frontal cortex during AS and CUS, while D(2)-like receptors were unchanged in all the brain regions studied. Locomotor activity was significantly decreased in both the stress models, A 68930 pretreatment significantly increased stereotypic counts and horizontal activity. Thus, present investigation provide insights into the differential regional response of dopaminergic system during AS and CUS. Further, neurochemical and behavioral effects of D(1) agonist pretreatment suggest specific modulatory role of D(1) receptor under such stressful episodes.

The effect of 'two hit' neonatal and young-adult stress on dopaminergic modulation of prepulse inhibition and dopamine receptor density

BACKGROUND AND PURPOSE

A combination of early neurodevelopmental insult(s) and young-adult stress exposure may be involved in the development of schizophrenia. We studied prepulse inhibition (PPI) regulation in rats after an early stress, maternal deprivation, combined with a later stress, simulated by chronic corticosterone treatment, and also determined whether changes in brain dopamine receptor density were involved.

EXPERIMENTAL APPROACH

Rats were subjected to either 24 h maternal deprivation on postnatal day 9, corticosterone treatment from 8 to 10 weeks of age, or both. At 12 weeks of age, the rats were injected with 0.1, 0.3 or 1.0 mg.kg(-1) of apomorphine or 0.5 or 2.5 mg.kg(-1) of amphetamine and PPI was determined using automated startle boxes. Dopamine D(1) and D(2) receptor levels were assessed in the nucleus accumbens and caudate nucleus using receptor autoradiography.

KEY RESULTS

Young-adult treatment with corticosterone resulted in attenuated disruption of PPI by apomorphine and amphetamine. In some rats, maternal deprivation resulted in reduced baseline PPI which added to the effect of corticosterone treatment. There was no down-regulation of dopamine D(1) or D(2) receptors.

CONCLUSIONS AND IMPLICATIONS

These results confirm and extend our finding of an inhibitory interaction of developmental stress on dopaminergic regulation of PPI. No corresponding changes in dopamine receptor density were observed in brain regions with a major involvement in PPI regulation, suggesting long-lasting desensitization of dopamine receptor signalling or indirect changes in PPI regulation.

Possible neuroleptic malignant syndrome related to concomitant treatment with paroxetine and alprazolam

A 74-year-old man with depressive symptoms was admitted to a psychiatric hospital due to insomnia, loss of appetite, exhaustion, and agitation. Medical treatment was initiated at a daily dose of 20 mg paroxetine and 1.2 mg alprazolam. On the 10th day of paroxetine and alprazolam treatment, the patient exhibited marked psychomotor retardation, disorientation, and severe muscle rigidity with tremors. The patient had a fever (38.2 degrees C), fluctuating blood pressure (between 165/90 and 130/70 mg mm Hg), and severe extrapyramidal symptoms. Laboratory tests showed an elevation of creatine phosphokinase (2218 IU/L), aspartate aminotransferase (134 IU/L), alanine aminotransferase (78 IU/L), and BUN (27.9 mg/ml) levels. The patient received bromocriptine and diazepam to treat his symptoms. 7 days later, the fever disappeared and the patient's serum CPK levels were normalized (175 IU/L). This patient presented with symptoms of neuroleptic malignant syndrome (NMS), thus demonstrating that NMS-like symptoms can occur after combined paroxetine and alprazolam treatment. The adverse drug reaction score obtained by the Naranjo algorithm was 6 in our case, indicating a probable relationship between the patient's NMS-like adverse symptoms and the combined treatment used in this case. The involvement of physiologic and environmental aspects specific to this patient was suspected. Several risk factors for NMS should be noted in elderly depressive patients whose symptoms often include dehydration, agitation, malnutrition, and exhaustion. Careful therapeutic intervention is necessary in cases involving elderly patients who suffer from depression.

The neurobiology and control of anxious states

Fear is an adaptive component of the acute "stress" response to potentially-dangerous (external and internal) stimuli which threaten to perturb homeostasis. However, when disproportional in intensity, chronic and/or irreversible, or not associated with any genuine risk, it may be symptomatic of a debilitating anxious state: for example, social phobia, panic attacks or generalized anxiety disorder. In view of the importance of guaranteeing an appropriate emotional response to aversive events, it is not surprising that a diversity of mechanisms are involved in the induction and inhibition of anxious states. Apart from conventional neurotransmitters, such as monoamines, gamma-amino-butyric acid (GABA) and glutamate, many other modulators have been implicated, including: adenosine, cannabinoids, numerous neuropeptides, hormones, neurotrophins, cytokines and several cellular mediators. Accordingly, though benzodiazepines (which reinforce transmission at GABA(A) receptors), serotonin (5-HT)(1A) receptor agonists and 5-HT reuptake inhibitors are currently the principle drugs employed in the management of anxiety disorders, there is considerable scope for the development of alternative therapies. In addition to cellular, anatomical and neurochemical strategies, behavioral models are indispensable for the characterization of anxious states and their modulation. Amongst diverse paradigms, conflict procedures--in which subjects experience opposing impulses of desire and fear--are of especial conceptual and therapeutic pertinence. For example, in the Vogel Conflict Test (VCT), the ability of drugs to release punishment-suppressed drinking behavior is evaluated. In reviewing the neurobiology of anxious states, the present article focuses in particular upon: the multifarious and complex roles of individual modulators, often as a function of the specific receptor type and neuronal substrate involved in their actions; novel targets for the management of anxiety disorders; the influence of neurotransmitters and other agents upon performance in the VCT; data acquired from complementary pharmacological and genetic strategies and, finally, several open questions likely to orientate future experimental- and clinical-research. In view of the recent proliferation of mechanisms implicated in the pathogenesis, modulation and, potentially, treatment of anxiety disorders, this is an opportune moment to survey their functional and pathophysiological significance, and to assess their influence upon performance in the VCT and other models of potential anxiolytic properties.

A dopamine D(1/5) receptor antagonist, SCH23390, prevents stress-induced sudden death in cardiomyopathic hamsters

Stress is known to have an impact on the development of life-threatening cardiovascular dysfunction. We have previously demonstrated that repeated exposure to cold-immobilization stress had lethal effects on cardiomyopathic Syrian hamsters (BIO 14.6), and that stress-induced sudden death was prevented by daily treatment with propranolol, suggesting an important role of sympathetic nerves in the etiology of stress-induced cardiac sudden death. In an attempt to clarify further the mechanisms of the sudden death, in the present study we investigated the effects of D(1/5) receptor blockade by SCH23390 on the sudden death of cardiomyopathic hamsters. In accordance with our previous results, repeated exposure for 5 days to cold-immobilization stress induced a lethal effect in the cardiomyopathic hamsters but not in control healthy hamsters. SCH23390 (0.1-10 mg/kg, IP), administered just before the exposure for 5 consecutive days, dose-dependently and significantly prevented the lethal effects of the stress. Furthermore, it was demonstrated that the drug significantly reduced the increase in the weights of the adrenal and kidneys observed in the stressed-cardiomyopathic hamsters. On the other hand, specific D(2) antagonist haloperidol (0. 1-10 mg/kg) failed to prevent the stress-induced sudden death and minimally affected the increase in organ weights. Collectively, these results suggest that D(1/5) receptors had an important role in the etiology of stress-induced cardiac sudden death of the cardiomyopathic hamsters, and provide the first experimental evidence of the potential therapeutic values of D(1/5) antagonists against cardiac sudden death associated with stress.

Effects of alprazolam on the free-choice ethanol consumption induced by isolation stress in aged rats

Late-onset drinking is a common problem in elderly people related to stress induced by social isolation. Experiments were performed in order to evaluate the effects of alprazolam, a benzodiazepine agonist anxiolytic, on the free-choice ethanol consumption in aged rats subjected to isolation stress. The animals we offered a two-bottle choice consumption (one of 0.2% saccharin and the other with 10% ethanol/0.2% saccharin) and then exposed to 4 days of isolation stress on an irregular, unpredictable schedule. Stress resulted in significant increase in ethanol consumption. Treatment with alprazolam (1 mg/Kg) partially reversed this adverse effect of stress.

Regulation of CCK mRNA expression in the rat brain by stress and treatment with sertraline, a selective serotonin re-uptake inhibitor

In this paper, we have investigated the regulation of CCK mRNA expression in the brain after restraint stress with and without long-term treatment with the selective serotonin reuptake inhibitor sertraline. Stress alone increases CCK mRNA levels in the hippocampus, whereas no changes were found in the cerebral cortex, amygdaloid complex and thalamus. CCK mRNA expression decreases in the hippocampus, increases in the thalamus and was not modified in the cerebral cortex and amygdaloid complex after sertraline alone. CCK mRNA content was unchanged in all investigated areas after stress plus sertraline compared to control rats.