Low-dose naltrexone inhibits pemoline-induced self-biting behavior in prepubertal rats

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 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.

Pemoline (2-amino-5-phenyl-1,3-oxazol-4-one)-induced self-injurious behavior: a rodent model of pharmacotherapeutic efficacy

Self-injury is a devastating, maladaptive behavior disorder that is common in developmental disabilities and is comorbid with numerous psychiatric disorders. Examples of self-injurious behavior (SIB) include head-banging, self-biting, and self-punching. The neurochemical basis of SIB is unknown; however, many different classes of drugs are prescribed (e.g., neuroleptics, atypical neuroleptics, anti-epileptics, opioid antagonists) to reduce these behaviors. These drugs have all shown clinically significant but limited efficacy in patient populations, and no class of drug is effective for all patients. The development and characterization of a valid animal model could provide important information regarding the neurochemical basis of SIB and could be used to screen potential new pharmacotherapies. In one model of SIB, high doses of pemoline (2-amino-5-phenyl-1,3-oxazol-4-one) are administered to rats. Using this model, we evaluated the effectiveness of three drugs (risperidone, valproate, and topiramate) that reduce SIB in humans. We also screened the potential effectiveness of tramadol, a drug that decreases stereotyped and compulsive behaviors but has not been assessed in human self-injurers. We found that risperidone, valproate, and topiramate each significantly attenuate pemoline-induced SIB, whereas tramadol does not. These findings suggest that the pemoline model of SIB has predictive validity across a range of drug classes and implicate important potential neurochemical mechanisms that may contribute to the behavior disorder. The findings also indicate that tramadol may not be an effective pharmacotherapy for SIB.

Paradoxical effects of serotonin and opioids in pemoline-induced self-injurious behavior

Self-injurious behavior (SIB) is a symptom of various psychiatric disorders with differing etiologies. Although no generally effective pharmacological treatment of SIB is available, subsets of individuals exhibiting SIB have been found to respond to opioid antagonists and selective serotonin reuptake inhibitors (SSRIs). The present study evaluated the efficacy of these two treatments in the pemoline-induced model of self-biting behavior (SBB) in rats. Using a factorial design, adult rats receiving daily pemoline at 100 mg/kg or the peanut oil vehicle were pretreated with either distilled water vehicle (1 cc/kg), naltrexone (1 mg/kg), or paroxetine (1 mg/kg). Each day, animals were rated on the severity of SBB and also periodically behavioral changes were evaluated using various other outcome measures. Paroxetine significantly increased the severity of SBB induced by pemoline, while naltrexone only marginally increased the SBB. These results were not expected and suggest that further studies into the role of serotonin agonists and antagonists are needed in evaluating this model.

Cortical damage enhances pemoline-induced self-injurious behavior in prepubertal rats

Self-injurious behavior (SIB) is a devastating characteristic of several developmental disorders including a number of mental retardation syndromes. The functional neuroanatomy and neuropharmacology of SIB is not well understood. Self-biting behavior (SBB) can be induced in rats by a high dose, systemic injection of pemoline (250 mg/kg, SC). This animal model allows for the investigation of anatomical and pharmacological aspects of SIB. Cortical pathology is a common occurrence in human disorders with SIB, and may be a fundamental pathological factor in producing the behavior. The present experiment was designed to investigate the effects of cortical damage on pemoline-induced SBB in prepubertal rats. Bilateral cortical aspirations were performed in 3-5-week-old rats. One week postsurgery, a pemoline challenge was administered. Behavioral comparisons were completed between the lesion group and an anesthetized-only control group. Results indicated that cortical damage significantly enhanced pemoline-induced SBB, along with some of the other pemoline-induced stereotypical behaviors. These results support the hypothesis that cortical damage influences the expression of stimulant-induced self-injury, and potential mechanisms for this influence are suggested.

Pemoline produces ipsilateral turning behavior in unilateral 6-OHDA-lesioned rats

1. Male Sprague-Dawley rats received either a unilateral injection of 6-hydroxy-dopamine or vehicle injection into the medial forebrain bundle. 2. Two weeks post surgery, all rats received a pemoline challenge (250 mg/kg s.c.), and rotational and stereotyped behaviors were videotaped and analyzed. 3. All rats regardless of injection expressed stereotyped behaviors and hyper-locomotion after pemoline challenge. 4. High performance liquid chromatography (HPLC) with electrochemical detection was used to evaluate changes in the levels of dopamine, serotonin and their metabolites in neostriata. 5. Rats with dopamine depleting lesions exhibited ipsilateral rotational behavior, indicating that pemoline, a central stimulant, is an indirect dopamine agonist in the rat. 6. The extent of dopamine depletion and serotonin elevation in the neostriatum in lesioned animals was related to the expression and degree of rotational behavior.