Hereditary compulsive self-mutillating behaviour in laboratory rabbits

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.

Rabbit Behavior

Rabbits are the third most common mammalian pet in the United States. They make good pets because they generally are nonaggressive and are playful, active, and curious. They form strong social bonds, both with rabbits they live with in the household and with the humans who care for them. They have several behaviors derived from their wild counterparts that can cause problems, if not properly allowed for, or be beneficial, such as their proclivity to use a specific site for elimination.

Human Infant Pants for Postoperative Protection during Social Housing of New Zealand White Rabbits (Oryctolagus cuniculus)

Elizabethan collars (E-collars) are commonly used in various species to safeguard healing wounds. However, E-collars inadvertently restrict the expression of normal species-typical behaviors, including coprophagy, self-grooming, and social housing. To maintain social housing in accordance with recommendations in the 8th edition of the Guide for the Care and Use of Laboratory Animals, we implemented the use of human infant pants instead of E-collars for postsurgical protection. We retrospectively reviewed the medical records of 154 intact male New Zealand white rabbits (age, 2 to 3 mo) regarding the use of E-collars (group 1; n = 72) compared with human infant pants (group 2; n = 82) for postoperative protection after 308 femoral angioplasty procedures. Maintenance of social pairs throughout the postoperative phase, replacement rate of infant pants, and self-mutilation rates were measured. Our findings indicate that using infant pants for postoperative protection was most successful in maintaining social housing, offers a more cost-effective option to E-collars, and does not increase the rate of self-mutilation in intact male New Zealand white rabbits.

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.

Suicide among Animals: Clues from Folklore That May Prevent Suicidal Behaviour in Human Beings

Knowing the most likely reasons for suicide might increase the chances to identify the early signs of suicide. Folkloric tales on suicide among animals are a possible source of such information, since people probably explain animal suicide using the same reasons they would apply to their kin. Modern naturalistic studies have found little evidence of self-harming conduct among nonhuman species. Nevertheless, mythological accounts often report suicidal behaviour among animals. Claudius Aelian's De natura animalium, a classic in its genre, written in the 2nd century AD, reports 21 cases of suicide among animals. In Aelian's tales, the severing of social ties emerges as an important motive for suicide, together with incest and rage caused by adultery. Paying attention to the mechanisms leading to suicide described in ancient mythology may help us understand unusual and uncommon motives for suicide and the reasons people feel suicidal.

Suicide among Animals: A Review of Evidence

Naturalists have not identified suicide in nonhuman species in field situations, despite intensive study of thousands of animal species. In this review, evidence on suicidal behavior among animals is analyzed to discover analogies with human suicidal behavior. Literature was retrieved by exploring Medline/PubMed and PsychINFO databases (1967–2007) and through manual literature searches. Keyword terms were “suicide or suicidal behavior” and “animal or animal behavior.” Few empirical investigations have been carried out on this topic. Nevertheless, sparse evidence supports some resemblance between the self-endangering behavior observed in the animal kingdom, particularly in animals held in captivity or put under pressure by environmental challenges, and suicidal behavior among humans. Animal models have contributed to the study of both normal and pathological human behaviors: discovering some correlates of suicide among animals could be a valid contribution to the field.

Biology and Diseases of Rabbits

Beginning in 1931, an inbred rabbit colony was developed at the Phipps Institute for the Study, Treatment and Prevention of Tuberculosis at the University of Pennsylvania. This colony was used to study natural resistance to infection with tuberculosis (Robertson et al., 1966). Other inbred colonies or well-defined breeding colonies were also developed at the University of Illinois College of Medicine Center for Genetics, the Laboratories of the International Health Division of The Rockefeller Foundation, the University of Utrecht in the Netherlands, and Jackson Laboratories. These colonies were moved or closed in the years to follow. Since 1973, the U.S. Department of Agriculture has reported the total number of certain species of animals used by registered research facilities (1997). In 1973, 447,570 rabbits were used in research. There has been an overall decrease in numbers of rabbits used. This decreasing trend started in the mid-1990s. In 2010, 210,172 rabbits were used in research. Despite the overall drop in the number used in research, the rabbit is still a valuable model and tool for many disciplines.

Self-mutilation and suicide attempts: relationships to bipolar disorder, borderline personality disorder, temperament and character

OBJECTIVE

Self-mutilation has traditionally been associated with borderline personality disorder, and seldom examined separately from suicide attempts. Clinical experience suggests that self-mutilation is common in bipolar disorder.

METHODS

A family study was conducted on the molecular genetics of depression and personality, in which the proband had been treated for depression. All probands and parents or siblings were interviewed with a structured interview and completed the Temperament and Character Inventory.

RESULTS

Fourteen per cent of subjects interviewed reported a history of self-mutilation, mostly by wrist cutting. Self-mutilation was more common in bipolar I disorder subjects then in any other diagnostic groups. In multiple logistic regression self-mutilation was predicted by mood disorder diagnosis and harm avoidance, but not by borderline personality disorder. Furthermore, the relatives of non-bipolar depressed probands with self-mutilation had higher rates of bipolar I or II disorder and higher rates of self-mutilation. Sixteen per cent of subjects reported suicide attempts and these were most common in those with bipolar I disorder and in those with borderline personality disorder. On multiple logistic regression, however, only mood disorder diagnosis and harm avoidance predicted suicide attempts. Suicide attempts, unlike self-mutilation, were not familial.

CONCLUSIONS

Self-mutilation and suicide attempts are only partially overlapping behaviours, although both are predicted by mood disorder diagnosis and harm avoidance. Self-mutilation has a particularly strong association with bipolar disorder. Clinicians need to think of bipolar disorder, not borderline personality disorder, when assessing an individual who has a history of self-mutilation.

Genetic, developmental and personality correlates of self-mutilation in depressed patients

OBJECTIVE

To examine whether the T allele of G protein beta3 (GNbeta3) is associated with self-mutilation in depressed patients.

METHOD

A history of self-mutilation was systematically inquired about when recruiting depressed patients for a long-term treatment trial. Risk factors such as borderline personality disorder and childhood abuse experiences were systematically assessed, and patients were genotyped for polymorphisms of GNbeta3.

RESULTS

The T allele of GNbeta3, borderline personality disorder and childhood sexual abuse were all significantly associated with self-mutilation in depressed patients. These associations were significant in both univariate and multivariate analyses, and as predicted were stronger in young depressed patients than in depressed patients of all ages.

CONCLUSIONS

If the association between the T allele of GNbeta3 and self-mutilation can be replicated, this may provide clues to understanding the neurobiology of self-mutilation.