Nifedipine suppresses self-injurious behaviors in animals

The neuropathology of Self-Injurious Behavior: Studies using animal models

Self-injurious behavior is a debilitating characteristic that is highly prevalent in autism and other neurodevelopmental disorders. In these populations, self-injury has typically been interpreted in relation to behavioral reinforcement and/or sensory stimulation. However, self-injury is also commonly exhibited by people with a variety of neuropsychiatric disorders, where it is typically described in relation to emotional regulation and the presence or absence of suicidal ideation. Interestingly, self-injury has also been documented in many non-human animal species, especially when exposed to early environmental deprivation, isolation, and distress. Despite the propensity of animals to self-injure under adverse conditions, animal models of self-injury have not been the focus of much research, and translation of the data from these models has largely been limited to autism and neurodevelopmental disorders. This review summarizes evidence that common biological and environmental mechanisms may contribute to vulnerability for self-injury in neurodevelopmental disorders, psychiatric disorders, and distressed animals, and that investigations using animal models may be highly beneficial when considering self-injury as a behavioral phenotype that exists across diagnostic categories. Investigations using animal models have revealed that individual differences in stress responses and anxiety-related behavior contribute to vulnerability for self-injury. Animal models have implicated dysregulation of monoaminergic, glutamatergic, and other neurotransmitter systems in expression of self-injury, and these models have suggested neural targets for pharmacotherapy that have potential relevance for diverse clinical populations.

Pharmacological Treatments for Methamphetamine Use Disorder: Current Status and Future Targets

The illicit use of the psychostimulant methamphetamine (METH) is a major concern, with overdose deaths increasing substantially since the mid-2010s. One challenge to treating METH use disorder (MUD), as with other psychostimulant use disorders, is that there are no available pharmacotherapies that can reduce cravings and help individuals achieve abstinence. The purpose of the current review is to discuss the molecular targets that have been tested in assays measuring the physiological, the cognitive, and the reinforcing effects of METH in both animals and humans. Several drugs show promise as potential pharmacotherapies for MUD when tested in animals, but fail to produce long-term changes in METH use in dependent individuals (eg, modafinil, antipsychotic medications, baclofen). However, these drugs, plus medications like atomoxetine and varenicline, may be better served as treatments to ameliorate the psychotomimetic effects of METH or to reverse METH-induced cognitive deficits. Preclinical studies show that vesicular monoamine transporter 2 inhibitors, metabotropic glutamate receptor ligands, and trace amine-associated receptor agonists are efficacious in attenuating the reinforcing effects of METH; however, clinical studies are needed to determine if these drugs effectively treat MUD. In addition to screening these compounds in individuals with MUD, potential future directions include increased emphasis on sex differences in preclinical studies and utilization of pharmacogenetic approaches to determine if genetic variances are predictive of treatment outcomes. These future directions can help lead to better interventions for treating MUD.

A mink (Neovison vison) model of self-injury: Effects of CBP-CREB axis on neuronal damage and behavior

Objective

Self-injurious behavior (SIB) is a clinically challenging problem in the general population and several clinical disorders. However, the precise molecular mechanism of SIB is still not clear. In this paper, the systematic investigation of the genesis and development of SIB is conducted based on behavioral and pathophysiology studies in mink (Neovison vison) models.

Method

The night-vision video was used to observe the mink behavior, and the duration was a month. HE stain was performed to characterize the pathology change in the brain of a mink. IHC assay was performed to conduct the protein level detection of Iba-1, p-CREB, CBP, and p300 in the brain tissues. Elisa assay was used to examine the levels of NfL and NfH in serum and CSF of mink. The qRT-PCR assay was used to detect the expression of Bcl-2, NOR1, FoxO4, c-FOS, CBP, and p300 in brain tissues. Western blot was used to detect the protein levels of p-CREB, CBP, and p300 in brain tissues. We also used Evans Blue as a tracer to detect whether the blood-brain barrier was impaired in the brain of mink.

Result

The behavioral test, histopathological and molecular biology experiments were combined in this paper, and the results showed that CBP was related to SIB. Mechanism analysis showed that the dysregulation of CBP in brain-activated CREB signaling will result in nerve damage of the brain and SIB symptoms in minks. More importantly, the CBP-CREB interaction inhibitor might help relieve SIB and nerve damage in brain tissues.

Conclusion

Our results illustrate that the induction of CBP and the activation of CREB are novel mechanisms in the genesis of SIB. This finding indicates that the CBP-CREB axis is critical for SIB and demonstrates the efficacy of the CBP-CREB interaction inhibitor in treating these behaviors.

The Pemoline Model of Self-Injurious Behavior: An Update

Neurodevelopmental disorders typically comprise a complex constellation of behavioral symptoms and neurochemical abnormalities. However, many of the symptoms are inconsistently expressed within any one particular patient group or overlap between patient groups. In other words, there is usually heterogeneity of symptoms between diagnostic groups, and there is often partial homogeneity of symptoms across these groups. These include cognitive deficits, emotional lability, and perseverative or aberrant behaviors. Animal models of neurodevelopmental disorders typically reproduce or mimic specific genetic, neurochemical, and/or behavioral sequelae, although they typically fail to replicate the entire spectrum of biological and behavioral characteristics. Indeed, it may be impractical or even impossible to model the entire spectrum of characteristics of a disorder in any single animal model. A focus on one or more specific behavioral characteristics that occur in multiple neurodevelopmental disorders (e.g., self-injury) may be a fruitful strategy. The development of these behaviorally focused models may yield increased understanding of the endogenous and environmental factors that confer vulnerability for aberrant behaviors that commonly occur in these disorders. One such behaviorally focused animal model is the pemoline model of self-injurious behavior.

Animal Models of Self-Injurious Behavior: An Update

Although self-injurious behavior is a common comorbid behavior problem among individuals with neurodevelopmental disorders, little is known about its etiology and underlying neurobiology. Interestingly, it shows up in various forms across patient groups with distinct genetic errors and diagnostic categories. This suggests that there may be shared neuropathology that confers vulnerability in these disparate groups. Convergent evidence from clinical pharmacotherapy, brain imaging studies, postmortem neurochemical analyses, and animal models indicates that dopaminergic insufficiency is a key contributing factor. This chapter provides an overview of studies in which animal models have been used to investigate the biochemical basis of self-injury and highlights the convergence in findings between these models and expression of self-injury in humans.

The role of anxiety in vulnerability for self-injurious behaviour: studies in a rodent model

Self-injurious behaviour (SIB) is a debilitating characteristic that is highly prevalent in autism and other neurodevelopmental disorders. Pathological anxiety is also common, and there are reports of comorbid anxiety and self-injury in some children. We have investigated potential interactions between anxiety and self-injury, using a rat model of pemoline-induced self-biting. In one experiment, rats were pre-screened for trait anxiety by measuring expression of anxiety-related behaviour on the elevated plus maze and open field emergence test. The rats were then treated with pemoline once daily for ten days, and vulnerability for pemoline-induced self-injury was evaluated. This revealed modest correlations between innate levels of anxiety-related behaviour in the open field test (time in the start box, and latency to enter the open field), and vulnerability for pemoline-induced self-biting (total duration of self-injurious oral contact, and total size of tissue injury). Measures in the elevated plus maze were not significantly correlated with vulnerability for pemoline-induced self-injury. In a second experiment, rats were treated with the beta-carboline FG 7142 twice daily, during 5days of treatment with pemoline. The rats that were treated with this anxiogenic drug exhibited greater duration of self-injurious oral contact, and larger injuries than vehicle-treated controls did. Overall, these results suggest that anxiety may contribute to the etiology and/or expression of self-injurious behaviour, and indicate that further research is warranted.

The Addictive Model of Self-Harming (Non-suicidal and Suicidal) Behavior

INTRODUCTION

Behavioral addictions such as gambling, sun-tanning, shopping, Internet use, work, exercise, or even love and sex are frequent, and share many characteristics and common neurobiological and genetic underpinnings with substance addictions (i.e., tolerance, withdrawal, and relapse). Recent literature suggests that both non-suicidal self-injury (NSSI) and suicidal behavior (SB) can also be conceptualized as addictions. The major aim of this mini review is to review the literature and explore the neurobiological and psychological mechanisms underlying the addiction to self-harming behaviors.

METHOD

This is a narrative review. The authors performed literature searches in PubMed and Google for suicidal behavior, self-harming, addiction, and "major repeaters." Given the scarce literature on the topic, a subset of the most closely related studies was selected. The authors also focused on three empirical studies testing the hypothesis that major repeaters (individuals with ≥5 lifetime suicide attempts) represent a distinctive suicidal phenotype and are the individuals at risk of developing an addiction to SB.

RESULTS

The authors reviewed the concept of behavioral addictions and major repeaters, current empirical evidence testing concerning whether or not NSSI and SB can be understood as "addictions," and the putative mechanisms underlying them.

CONCLUSION

Our review suggests that both NSSI and SB can be conceptualized as addictions. This is relevant because if some individual's self-harming behaviors are better conceptualized as an addiction, treatment approaches could be tailored to this addiction.

Multidisciplinary assessment and treatment of self-injurious behavior in autism spectrum disorder and intellectual disability: integration of psychological and biological theory and approach

The objective of this review is to consider the psychological (largely behavioral) and biological [neurochemical, medical (including genetic), and pharmacological] theories and approaches that contribute to current thinking about the etiology and treatment of self-injurious behavior (SIB) in individuals with autism spectrum disorder and/or intellectual disability. Algorithms for the assessment and treatment of SIB in this context, respectively, from a multidisciplinary, integrative perspective are proposed and challenges and opportunities that exist in clinical and research settings are discussed.

Self-injurious behaviour in autistic children: a neuro-developmental theory of social and environmental isolation

RATIONALE

Self-injurious behaviour is not one of the three core symptoms that define autism. However, children on the autism spectrum appear to be particularly vulnerable. Afflicted children typically slap their faces, punch or bang their heads, and bite or pinch themselves. These behaviours can be extremely destructive, and they interfere with normal social and educational activities. However, the neurobiological mechanisms that confer vulnerability in children with autism have not been adequately described.

OBJECTIVES

This review explores behavioural and neurobiological characteristics of children with autism that may be relevant for an increased understanding of their vulnerability for self-injurious behaviour.

METHODS

Behavioural characteristics that are co-morbid for self-injurious behaviour in children with autism are examined. In addition, the contributions of social and environmental deprivation in self-injurious institutionalized orphans, isolated rhesus macaques, and additional animal models are reviewed.

RESULTS

There is extensive evidence that social and environmental deprivation promotes self-injurious behaviour in both humans (including children with autism) and animal models. Moreover, there are multiple lines of convergent neuroanatomical, neurophysiological, and neurochemical data that draw parallels between self-injurious children with autism and environmentally deprived humans and animals.

CONCLUSIONS

A hypothesis is presented that describes how the core symptoms of autism make these children particularly vulnerable for self-injurious behaviour. Relevant neurodevelopmental pathology is described in cortical, limbic, and basal ganglia brain regions, and additional research is suggested.

The pemoline model of self-injurious behaviour

Traditional models of neuropsychiatric disorders consist of attempts to replicate the broad spectrum of behavioural and neurochemical sequelae that characterize a specific disorder. However, these disorders comprise complex constellations of symptoms, including emotional instability, perseverative thoughts, and aberrant behaviours. Close examination often reveals heterogeneity of symptom expression within patient groups and homogeneity in expression of specific symptoms across diagnostic categories. Accordingly, it may not be possible to model the entire spectrum of characteristics for any one of these disorders in any single animal model. A focus on one or more specific behavioural characteristics (e.g. self-injury) may be a more fruitful strategy. Development of behaviourally focused models yields increased understanding of the genetic basis and biochemical abnormalities that underlie specific psychiatric dysfunctions. Furthermore, by revealing pathophysiology that underlies specific disease characteristics, behaviourally focused models improve translational power and help to identify targets for effective pharmacotherapies. One such behaviourally focused animal model is the pemoline model of self-injurious behaviour.

Animal models of self-injurious behaviour: an overview

Self-injurious behaviour is highly prevalent in neurodevelopmental disorders. Interestingly, it is not restricted to any individual diagnostic group. Rather, it is exhibited in various forms across patient groups with distinct genetic defects and classifications of disorders. This suggests that there may be shared neuropathology that confers vulnerability. Convergent evidence from clinical pharmacotherapy, brain imaging studies, postmortem neurochemical analyses, and animal models indicates that dopaminergic insufficiency is a key culprit. This chapter provides an overview of studies in which animal models have been used to investigate the biochemical basis of self-injury, and highlights the convergence in findings between these models and expression of self-injury in humans.

Individual differences in vulnerability for self-injurious behavior: studies using an animal model

Self-injurious behavior (SIB) is a debilitating characteristic that is prevalent across a broad spectrum of neurodevelopmental disorders. In most of these disorders, some individuals exhibit SIB, whereas others do not. However, the neurobiological mechanisms that confer vulnerability are virtually unexplored. We examined innate characteristics that contribute to vulnerability or resistance for SIB in an animal model of the behavioral pathology. Eighteen outbred Long-Evans rats were screened for behavioral responsiveness to the mild stress of a novel environment. The rats were then categorized as high responders (HR; those rats that had the highest locomotor counts) or low responders (LR; those rats that had lower locomotor counts) by median split. All the rats were then given daily injections of the indirect monoamine agonist pemoline (150 mg/kg/day) for 10 days, and self-injury was evaluated. All 9 HR rats and 5 of the 9 LR rats exhibited self-injury. The HR rats spent more time self-injuring, injured more body sites, and caused larger areas of tissue damage than the LR rats did. Furthermore, the behavioral responsiveness to novelty stress was significantly correlated with each of these measures of self-injury. The HR rats did not exhibit substantially enhanced responses on other measures of psychostimulant action (stereotypy, grooming, locomotion, rearing). Accordingly, vulnerability to develop pemoline-induced SIB is positively correlated with, and can be predicted based upon, a behavioral measure of innate stress responsiveness. These findings suggest that characteristics that are common in developmental disorders may help predispose afflicted individuals to self-injure. The findings also extend the variety of behavioral pathologies (e.g. drug addiction) for which the HR/LR model predicts vulnerability.

Lesch-Nyhan disease: from mechanism to model and back again

Lesch-Nyhan disease (LND) is a rare inherited disorder caused by mutations in the gene encoding hypoxanthine-guanine phosphoribosyltransferase (HPRT). LND is characterized by overproduction of uric acid, leading to gouty arthritis and nephrolithiasis. Affected patients also have characteristic neurological and behavioral anomalies. Multiple cell models have been developed to study the molecular and metabolic aspects of LND, and several animal models have been developed to elucidate the basis for the neurobehavioral syndrome. The models have different strengths and weaknesses rendering them suitable for studying different aspects of the disease. The extensive modeling efforts in LND have questioned the concept that an 'ideal' disease model is one that replicates all of its features because the pathogenesis of different elements of the disease involves different mechanisms. Instead, the modeling efforts have suggested a more fruitful approach that involves developing specific models, each tailored for addressing specific experimental questions.

Experimental therapeutics for dystonia

Dystonia is a neurological syndrome characterized by excessive involuntary muscle contractions leading to twisting movements and unnatural postures. It has many different clinical manifestations, and many different causes. More than 3 million people worldwide suffer from dystonia, yet there are few broadly effective treatments. In the past decade, progress in research has advanced our understanding of the pathogenesis of dystonia to a point where drug discovery efforts are now feasible. Several strategies can be used to develop novel therapeutics for dystonia. Existing therapies have only modest efficacy, but may be refined and improved to increase benefits while reducing side effects. Identifying rational targets for drug intervention based on the pathogenesis of dystonia is another strategy. The surge in both basic and clinical research discoveries has provided insights at all levels, including etiological, physiological and nosological, to enable such a targeted approach. The empirical approach to drug discovery, whereby compounds are identified using a nonmechanistic strategy, is complementary to the rational approach. With the recent development of multiple animal models of dystonia, it is now possible to develop assays and perform drug screens on vast numbers of compounds. This multifaceted approach to drug discovery in dystonia will likely provide lead compounds that can then be translated for clinical use.

L-DOPA-induced activation of striatal p38MAPK and CREB in neonatal dopaminergic denervated rat: Relevance to self-injurious behavior

The destruction of nigrostriatal dopaminergic neurons with 6-hydroxydopamine (6OHDA) during the neonatal period results in dopamine (DA) loss and susceptibility for self-injurious behavior (SIB) when challenged with L-dihydroxyphenylalanine (L-DOPA), via a supersensitive D1 receptor-mediated mechanism. However, there are no changes in D1 receptor binding or mRNA levels, suggesting a potential postreceptor signaling mechanism(s). Here, we examined whether L-DOPA-induced SIB is associated with altered MAPK signaling (p38MAPK, ERK1/2, and JNK) and their nuclear target, CREB. Neonatal dopaminergic lesioned animals were challenged, as adults, with L-DOPA, observed for SIB for 6 hr, and then sacrificed. The data were grouped as follows: control, lesioned rats without SIB (SIB(-)), and lesioned rats that were positive for SIB (SIB(+)). HPLC analysis of striatal extracts revealed a more significant loss of DA and an increase of serotonin in the SIB(+) than in the SIB(-) group. The striatal levels of TH protein were severely decreased, but D1 receptor levels were unaltered in the lesioned groups. These results confirm and extend previous studies indicating that SIB is associated with a near-total loss of DA and TH, an increase in serotonin, and no change in D1 receptor levels. The present studies further revealed that the levels of active phosphorylated forms of p38MAPK and CREB were significantly higher in the SIB(+) group than in the SIB(-) group in the striatum, but not in cortex or olfactory tubercle. The results indicate an induction of striatal p38MAPK and an activation of its nuclear target, CREB, as additional mechanisms in the genesis of L-DOPA-induced SIB.

Glutamate-mediated neuroplasticity in an animal model of self-injurious behaviour

Self-injurious behaviour (SIB) is exhibited by individuals with a broad variety of developmental disorders and genetic abnormalities, including autism and Lesch-Nyhan, Prader-Willi and Rett syndromes. Most research has focused on environmental factors that reinforce SIB, and less is known about the biological basis of this behaviour disorder. However, animal models have been developed to study the neurochemical pathology that underlies SIB. In one model, rats exhibit self-biting after repeated daily administration of moderately high doses of pemoline (100-200mg/kg). Dopaminergic and glutamatergic neurotransmission have been implicated in this model. Accordingly, we investigated the role of glutamatergic neurotransmission in pemoline-induced SIB, using the N-methyl-d-aspartate (NMDA) receptor antagonists MK-801 and memantine. MK-801 is a high affinity antagonist which blocks glutamate-mediated neuroplasticity and behavioural sensitization to other psychostimulants. It lessened the incidence of SIB, the time spent self-injuring, and the area of tissue damage in the pemoline model. Memantine, on the other hand, is a low affinity antagonist which does not disrupt glutamate-mediated neuroplasticity, and it had little if any effect on any measure of pemoline-induced SIB. These results suggest that repeated pemoline administration induces glutamate-mediated neuroplastic changes that lead to the eventual expression of SIB. Further investigation of these changes may reveal specific neurochemical factors that contribute to SIB in this animal model of self-injury.