Marble kirkegård og Nestlet Shredding som Tester av repeterende, Compulsive-lignende atferd hos mus

Summary

Disease, head injury, genetic modifications, and treatment of mice with drugs can have profound effects on behavior. Utilizing well-characterized and validated approaches such as marble burying and nestlet shredding, compulsive-like behaviors can be documented accurately in mice as models of human obsessive-compulsive disorder and autism spectrum disorder.

Abstract

Tvangslidelse (OCD) og autismespekterforstyrrelser (ASD) er alvorlige og ødeleggende psykiatriske tilstander og hver utgjør et betydelig folkehelseproblem, særlig hos barn. Begge disse forholdene er fremhevet av gjentatte uttrykk for meningsløse atferd. Personer med OCD ofte vise kontroll, hyppig håndvask, og telling. Barn med ASDer også engasjere seg i repeterende tapping, arm eller hånd flagrende, og rocking. Denne oppførselen kan variere mye i intensitet og hyppighet av uttrykk. Mer intense former for repeterende atferd kan også føre til skade (for eksempel overdreven grooming, håndvask, og selvstimulering). Disse atferd er derfor svært forstyrrende og normal sosial diskurs vanskelig. Behandlingstilbud for repeterende atferd i OCD og ASDs er noe begrenset, og det er stor interesse for å utvikle mer effektive behandlingsformer for hver tilstand. Mange dyremodeller for evaluating tvangslignende atferd har blitt utviklet over de siste tre tiårene. Kanskje de dyremodeller med størst gyldighet og brukervennlighet er det marmor nedgraving test og nestlet shredding test. Begge testene dra nytte av det faktum at målet oppførsel oppstår spontant i mus. I marmor nedgraving test, er 20 klinkekuler kledd på overflaten av rent sengetøy. Antallet kuler begravd i en 30 min økt er scoret av etterforskere blinde til behandling eller status av fagene. I nestlet rivetesten, er en nestlet består av utgnidd bomullsfiber var veid på forhånd og plasseres på toppen av buret bedding og mengden av den resterende nestlet intakt etter 30 min testsesjon blir bestemt. I dag beskriver vi protokoller for og vise filmen dokumentasjon av marmor nedgraving og nestlet shredding. Begge testene er enkelt og nøyaktig scoret og hver er følsomme for små endringer i uttrykket av tvangslignende atferd som følge av genetisk manipulations, sykdom, eller hodeskade.

Introduction

Mouse models of human behaviors, and particularly psychiatric disorders, constitute important and essential experimental approaches to the study of disease mechanisms and to the development of new therapies. Many psychiatric illnesses remain extremely difficult to model in animals (e.g. schizophrenia). However, animals exhibit a large number of natural and distinctive behaviors that can readily be linked to similar behaviors in humans. Movement or locomotor activity is one example of a behavior in animals that has a counterpart in humans. Rodents often engage in a variety of repetitive behaviors and examples include grooming or digging. One psychiatric condition that involves the exhibition of recurrent and unwanted behaviors in humans is obsessive-compulsive disorder (OCD). Behaviors that are highly characteristic of OCD include checking, counting, and excessive washing or grooming. OCD is a highly prevalent (affects 1-3% of the population) and debilitating psychiatric disorder¹. A large number of pharmacological and behavioral approaches have been used to treat OCD. Many of these fall short of providing long-term relief and relapse is common at the end of a treatment regimen^2,3. Another psychiatric condition that involves the expression repetitive behaviors is autism spectrum disorder (ASD). ASDs are characterized by deficits in communication and social interaction and repetitive, stereotyped behaviors to include spinning, rocking, finger flicking or flapping, and complex body movements. The Centers for Disease Control and Prevention has estimated that about 1 in 88 children are diagnosed with ASDs. Treatment options for this disorder are extremely limited in number and efficacy^4,5. The intensity and frequency of occurrence of repetitive behaviors in OCD and ASD can become great enough to displace most other normal behaviors and social interactions in patients with these conditions. In light of the prevalence and debilitating nature of psychiatric conditions characterized by repetitive behaviors, and considering the poor understanding of their causes and limited treatment options, the use of animal models to study these behaviors takes on added urgency.

A large number of animal models of repetitive behaviors as seen in OCD and ASDs have been developed over the past 30 years and numerous excellent reviews describing these models have been published^6-14. In general, these established models can be classified as genetic, pharmacological, neurodevelopmental and behavioral and most show good face, construct and predictive validity^6,7. We have used two behavioral models- marble burying and nestlet shredding- to assess repetitive behaviors in mice genetically depleted of serotonin^15,16. These methods have numerous advantages not the least of which are their ease of use, the accuracy with which the behaviors can be scored, the spontaneous exhibition of these behaviors in rodents, and their use in high-throughput screening of genetically modified mice for abnormal behavioral phenotypes. Furthermore, each test is carried out in standard and familiar rodent housing cages containing the same bedding used in subjects' home cages, minimizing the need for habituation of mice to novel testing chambers. Food and/or water restriction are not required to "motivate" mice to perform. The marble burying test takes advantage of the proclivity of mice to dig in natural settings (e.g. burrows, escape tunnels) and in standard cage bedding, and the nestlet shred test capitalizes on the fact that mice are nesting animals by nature that build nests for protection of themselves and their offspring against environmental conditions (e.g. sound, light, temperature). Using nonspecialized and commonly available rodent housing materials, the marble burying and nestlet shredding tasks are simple and powerful behavioral assays of repetitive, compulsive-like behaviors in mice.

Protocol

All protocols using animals were carried out in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. The protocols were approved by the Institutional Care and Use Committee of Wayne State University (Permit Number A3310-01). 1. Preparation of Cages for Marble Burying and Nestlet Shredding Use standard polycarbonate rat cages (26 cm x 48 cm x 20 cm) with fitted filter-top covers for the marble b…

Representative Results

A primary advantage of the marble burying and nestlet shredding tests is the fact that each depends on natural and spontaneous behaviors of mice that can be quantified after test completion, allowing a single investigator to set up an experiment and then remain outside of the testing room until sessions end. A critical component of the marble burying test is the careful removal of the subject from the cage after testing. Mice typically attempt to avoid capture and, in the process, can dislodge or move marbles that were p…

Discussion

The marble burying and nestlet shredding tests are good examples of behavioral methods for studying repetitive and compulsive-like behaviors in mice. Both tests show excellent face, construct and predictive validity for the human disorders they model^6-11. These repetitive behaviors are natural and spontaneous in rodents and their frequency and intensity can vary after genetic modifications, as shown presently, or after head injury and treatment of subjects with drugs. The value of these two tests derives from …

Materials

Glass toy marbles	local toy store	N/A	assorted styles, colors, clear, and opaque
Nestlets	Ancare	NES3600
N10 series mouse cage	Ancare	N10HT	standard rodent cage with wire top
R20 series rat cage	Ancare	R20	standard rodent cage with wire top
Bed-o'Cobs	The Andersons	8B	standard rodent bulk bedding, 1/8 in