Rationale Research - PowerPoint Presentation

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Rationale

Research on the development of OCD is necessary to understand its pathophysiology. This is because the cause of OCD is unknown and pathophysiology cannot be elucidated unequivocally for any morbid condition of unknown cause (1). Without an identified causal agent, the available experimental paradigm to elucidate pathophysiology is the comparison of individuals with and without the condition. However, findings from such studies may indicatethe specific effects produced by the disease-producing agentthe normal compensation to perturbation from the morbid conditionthat the observed changes are actually from several morbid conditions with different causes. Clearly, to identify the pathophysiology of OCD unequivocally requires a paradigm where development of the morbid condition is followed chronologically from its very inception onwards. We have established an animal model—the quinpirole sensitization rat model of OCD—where the transformation from normal behavior to the OCD phenotype is under experimental control and develops over a course of several weeks, providing a preparation to isolate the neurobiological changes of OCD pathogenesis and identify its pathophysiology (2).

Objective

To

investigate the biological development of compulsive checking behavior with gene expression profiling in a rat model of OCD. As a preliminary step in such a project, here we report on the feasibility of using blood to track mRNA changes during induction of the OCD phenotype.

Conclusion

Analysis of rat behavior showed that, as expected, quinpirole-treated rats developed compulsive checking behavior. Analysis of the mRNA results indicates that of the 34 genes measured, differential gene expression between quinpirole- and saline- treated rats was not found, except in the case of the CST3 gene. Further experimentation is required in the collection and analysis of blood mRNA in the progression of the OCD phenotype to assess the feasibility of such a method for identifying the pathophysiology of OCD.

Search for the Molecular Signature of Pathogenesis of Obsessive-Compulsive Disorder (OCD) Paul Jung1; Tony Jung1; Lucshman Raveendran1; Yasamin Farbod2; James Murphy3; Kjetil Ask3; Jane Foster4; Anna Dvorkin-Gheva4; Boris Sakic4; Henry Szechtman4 1B.H.Sc. Candidate, Health Sciences Program, McMaster University; 2Hon.B.Sc., Life Sciences Program, McMaster University; 3Department of Medicine, Division of Nephrology, McMaster University; 4Department of Psychiatry and Behavioural Neurosciences, McMaster University

Methods

Long-Evans

rats were treated chronically with the D2/D3 dopamine agonist quinpirole (n=16; 0.25 mg/kg, weekly for five weeks, then twice weekly for two weeks), and compared to saline controls (n=16). Their movement was tracked using

EthoVision

software in a large open-field with 4 small objects. 1-3mL of blood was drawn depending on the size of the animal one day after injection every two weeks from the tail vein or, when necessary, the saphenous vein. RNA was isolated from blood samples (NucleoSpin RNA Plus protocol) and gene expression was quantified via

NanoString

nCounter analysis.

Results

As

expected, chronic treatment with quinpirole induced compulsive checking behavior. This is illustrated in Figure 1 where the quinpirole-treated rats are significantly different from saline controls on all the criteria measures for compulsive checking. Figure 2 shows the paths of locomotion in a representative saline and quinpirole rat, illustrating that development of compulsive checking is associated with a unique distribution of routes of travel.

Gene Expression

Changes

Behavioral Findings

Of the 34 genes analyzed, there were no significant differences in gene expression between quinpirole-

and saline-treated rats, except for the CST3 gene. Figures 3 and 4 below are dendrograms that show the hierarchial clustering of gene expression in each rat for each injection.

Figure 1: Progression of compulsive checking behavior and satiety in quinpirole- and saline-treated rats

Figure 2: Example pathplots of quinpirole- and saline-treated rats

34 genes were chosen for analysis based on previous research of genes implicated in OCD (3). They are shown in the table below.

ATF4 COX8A D4 GRP78 PFKFB4 TMEM33 YWHAB B2m CST3 D5 IL3RA PP1R9B TNF ACTB CD81 D1 DAT1 ILF3 Prolactin TST HPRT1 CDK4 D2 GABARAP MCP1 QDPR TyrosineHydroxylase PGK1 CHOP D3 GDI1 MT1A RHD XBP1 

Table 1: List of genes analyzed in detail

Figure 3: Dendrogram of injections 1, 3, 5, and 9

Figure 4:

Dendrogram

of injections 1 and 9 only

References

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H,

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W,

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D. Quinpirole induces compulsive checking behavior in rats: a potential animal model of obsessive-compulsive disorder (OCD).

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