Clomipramine, but not haloperidol or aripiprazole, inhibits quinpirole-induced water contrafreeloading, a putative animal model of compulsive behavior

Opening new vistas on obsessive-compulsive disorder with the observing response task

Obsessive-compulsive disorder (OCD), a highly prevalent and debilitating disorder, is incompletely understood in terms of underpinning behavioural, psychological, and neural mechanisms. This is attributable to high symptomatic heterogeneity; cardinal features comprise obsessions and compulsions, including clinical subcategories. While obsessive and intrusive thoughts are arguably unique to humans, dysfunctional behaviours analogous to those seen in clinical OCD have been examined in nonhuman animals. Genetic, ethological, pharmacological, and neurobehavioural approaches all contribute to understanding the emergence and persistence of compulsive behaviour. One behaviour of particular interest is maladaptive checking, whereby human patients excessively perform checking rituals despite these serving no purpose. Dysfunctional and excessive checking is the most common symptom associated with OCD and can be readily operationalised in rodents. This review considers animal models of OCD, the neural circuitries associated with impairments in habit-based and goal-directed behaviour, and how these may link to the compulsions observed in OCD. We further review the Observing Response Task (ORT), an appetitive instrumental learning procedure that distinguishes between functional and dysfunctional checking, with translational application in humans and rodents. By shedding light on the psychological and neural bases of compulsive-like checking, the ORT has potential to offer translational insights into the underlying mechanisms of OCD, in addition to being a platform for testing psychological and neurochemical treatment approaches.

Neuroreceptor kinetics in rats repeatedly exposed to quinpirole as a model for OCD

Background

Obsessive-compulsive disorder (OCD) is a chronic, incapacitating, early onset psychiatric disorder that is characterized by obsessions and compulsions originating from a disturbance in the cortico-striato-thalamico-cortical circuit. We implemented the preclinical quinpirole (QP) rat model for compulsive checking in OCD to analyse the behaviour and visualize the D2R, mGluR5 and GLT1 density in order to contribute to the understanding of the neuroreceptor kinetics.

Methods

Animals (n = 14) were exposed to either saline (1 mL/kg) or QP (dopamine D2-agonist, 0.5 mg/kg) twice-weekly during 7 weeks. After each injection animals were placed on an open field test. After model setup, animals were placed in a behavioural cage equipped with tracking software and hardware in order to analyse the behaviour. Subsequently, sagittal slides were made of the CP in the right hemisphere and a staining was done with the D2R, mGluR5 and GLT-1 antibody to visualize the corresponding receptor.

Results

The QP animals displayed a strong increase in travelled distance (+596.70%) and in the number of homebase visits (+1222.90%) compared to the control animals. After chronic exposure to QP, animals had a significantly (p < 0.05) higher percentage of D2R density in the CP (7.92% ± 0.48%) versus 6.66% ± 0.28% in animals treated with saline. There were no differences for mGluR5 and GLT1 receptor density.

Conclusions

Chronic exposure to QP leads to hyperlocomotion and an increase in D2R density. Furthermore, as mGluR5 and GLT1 density did not seem to be directly affected, decreased levels of glutamate might have influenced the binding potential in earlier reports.

Contrafreeloading in Rats Is Adaptive and Flexible: Support for an Animal Model of Compulsive Checking

Contrafreeloading involves working unnecessarily to obtain a reward that is otherwise freely available. It has been observed in numerous species and can be adaptive when it provides an organism with updated information about available resources. Humans frequently update their knowledge of the environment through checking behaviors. Compulsive checking occurs when such actions are performed with excessive frequency. In a putative animal model of compulsive checking, rats treated chronically with the dopamine agonist quinpirole display exaggerated contrafreeloading for water. Although this effect has been attributed to behavioral rigidity, some evidence suggests the behavior remains somewhat flexible and may be adaptive under certain conditions. We assessed the ability of quinpirole-treated rats with contrafreeloading experience to adapt to changing contingencies by requiring them to alternate between response levers. Rats treated with quinpirole or saline were first trained to obtain water by pressing either of two levers. Next, free water was made available for 8 days, and contrafreeloading was measured. Rates of contrafreeloading were significantly higher in the drug-treated rats than in controls. On the following 5 days, each reward caused the associated lever to become inactive until a reward was earned from the alternate lever. Quinpirole-treated rats learned this new response requirement more quickly than controls. Thus, exaggerated checking behavior induced by chronic quinpirole treatment can be advantageous when environmental contingencies change. These results provide support for this animal model of compulsive checking and hint at the presence of a specialized neural checking module involving the dopamine system.

Preclinical molecular imaging of glutamatergic and dopaminergic neuroreceptor kinetics in obsessive compulsive disorder

BACKGROUND

Molecular neuroimaging was applied in the quinpirole rat model for compulsive checking in OCD to visualize the D2- and mGluR5-receptor occupancy with Raclopride and ABP-688 microPET/CT.

METHODS

Animals (n=48) were exposed to either saline (CTRL; 1mL/kg) or quinpirole (QP; dopamine D2-agonist, 0.5mg/kg) in a single injection (RAC and ABP acute groups) or twice-weekly during 7weeks (chronic group). Animals underwent PET/CT after the 1st injection (acute) or before initial exposure and following the 10th injection in week 5 (chronic). For the latter, each injection was paired with an open field test and video tracking.

RESULTS

The QP animals displayed a strong increase in visiting frequency (checking) in the chronic group (+699.29%) compared to the control animals. Acute administration of the drug caused significant (p<0.01) decreases in D2R occupancy in the CP (-42.03%±4.01%). Chronical exposure resulted in significantly stronger decreases in the CP (-52.29%±3.79%). Furthermore significant increases in mGluR5 occupancy were found in the CP (10.36%±4.09%), anterior cingulate cortex (13.26%±4.01%), amygdala (24.36%±6.86%), entorhinal cortex (18.49%±5.14%) and nucleus accumbens (13.8%±4.87%) of the chronic group, not present after acute exposure.

CONCLUSIONS

Compared to acute exposure, sensitisation to QP as a model for OCD differs both on a dopaminergic and glutamateric level, indicating involvement of processes such as receptor internalization and changes in extracellular availability of both neurotransmitters.

Behavioral Biomarkers of Schizophrenia in High Drinker Rats: A Potential Endophenotype of Compulsive Neuropsychiatric Disorders

Psychogenic polydipsia, which is compulsive, non-regulatory fluid consumption, is present in 6%-20% of chronic psychiatric patients and frequently associated with the schizophrenia diagnosis. In the present study, we investigated the relation between schizophrenia-like symptoms and biomarkers with a compulsive drinking behavior phenotype in rats. Rats that were selected for low drinking vs high drinking behavior following schedule-induced polydipsia (SIP) were assessed in a latent inhibition (LI) paradigm using tone and electrical foot shock and in a spatial reversal learning task to evaluate behavioral inflexibility. We also analyzed the myelin basic protein in different brain areas of high drinker (HD) and low drinker (LD) rats. The HD rats, which were characterized by a compulsive drinking behavior on SIP, had a reduced level of LI effect and increased behavioral inflexibility in the spatial reversal learning task in comparison to the LD group. Moreover, HD rats showed less myelination in the center of the corpus callosum, striatum, and amygdala in comparison to LD rats. These findings strengthen the validity of HD rats that were selected by SIP as a possible phenotype of compulsive neuropsychiatric disorders, as evidenced by the existence of behaviors and biological markers that are related to schizophrenia and obsessive-compulsive disorder, including a reduced LI effect, behavioral inflexibility and reduced brain myelination. Future studies could contribute to the elucidation of the mechanisms underlying the compulsive phenotype of HD rats and its relation to vulnerability to schizophrenia.

Obsessive-compulsive disorder: Insights from animal models

Research with animal models of obsessive-compulsive disorder (OCD) shows the following: (1) Optogenetic studies in mice provide evidence for a plausible cause-effect relation between increased activity in cortico-basal ganglia-thalamo-cortical (CBGTC) circuits and OCD by demonstrating the induction of compulsive behavior with the experimental manipulation of the CBGTC circuit. (2) Parallel use of several animal models is a fruitful paradigm to examine the mechanisms of treatment effects of deep brain stimulation in distinct OCD endophenotypes. (3) Features of spontaneous behavior in deer mice constitute a rich platform to investigate the neurobiology of OCD, social ramifications of a compulsive phenotype, and test novel drugs. (4) Studies in animal models for psychiatric disorders comorbid with OCD suggest comorbidity may involve shared neural circuits controlling expression of compulsive behavior. (5) Analysis of compulsive behavior into its constitutive components provides evidence from an animal model for a motivational perspective on OCD. (6) Methods of behavioral analysis in an animal model translate to dissection of compulsive rituals in OCD patients, leading to diagnostic tests.

Validity of Quinpirole Sensitization Rat Model of OCD: Linking Evidence from Animal and Clinical Studies

Obsessive-compulsive disorder (OCD) is a neuropsychiatric disorder with 1–3% prevalence. OCD is characterized by recurrent thoughts (obsessions) and repetitive behaviors (compulsions). The pathophysiology of OCD remains unclear, stressing the importance of pre-clinical studies. The aim of this article is to critically review a proposed animal model of OCD that is characterized by the induction of compulsive checking and behavioral sensitization to the D2/D3 dopamine agonist quinpirole. Changes in this model have been reported at the level of brain structures, neurotransmitter systems and other neurophysiological aspects. In this review, we consider these alterations in relation to the clinical manifestations in OCD, with the aim to discuss and evaluate axes of validity of this model. Our analysis shows that some axes of validity of quinpirole sensitization model (QSM) are strongly supported by clinical findings, such as behavioral phenomenology or roles of brain structures. Evidence on predictive validity is contradictory and ambiguous. It is concluded that this model is useful in the context of searching for the underlying pathophysiological basis of the disorder because of the relatively strong biological similarities with OCD.

Detrimental effect of clomipramine on hippocampus-dependent learning in an animal model of obsessive-compulsive disorder induced by sensitization with d2/d3 agonist quinpirole

Quinpirole (QNP) sensitization is one of the commonly used animal models of obsessive-compulsive disorder (OCD). We have previously shown that QNP-sensitized animals display a robust cognitive flexibility deficit in an active place avoidance task with reversal in Carousel maze. This is in line with numerous human studies showing deficits in cognitive flexibility in OCD patients. Here we explored the effect of clomipramine, an effective OCD drug that attenuates compulsive checking in QNP, on sensitized rats in acquisition and reversal performances in an active place avoidance task. We found that the addition of clomipramine to QNP-sensitization impairs acquisition learning to a degree that reversal learning could not be tested. In a hippocampal-independent two-way active avoidance task clomipramine did not have an effect on acquisition learning in QNP-treated rats; suggesting that the detrimental effect of clomipramine is hippocampus based. We also tested the effect of risperidone in QNP-sensitized animals, which is not effective in OCD treatment. Risperidone also marginally impaired acquisition learning of QNP-sensitized animals, but not reversal. Moreover, we explored the effect of the augmentation of clomipramine treatment with risperidone in QNP-sensitized rats- a common step in treating SRI-unresponsive OCD patients. Only under this treatment regime animals were unimpaired in both acquisition and reversal learning. Augmentation of SRI with neuroleptics therefore could be beneficial for improving cognitive flexibility, and possibly be considered a first line of treatment in patients with reduced cognitive flexibility.

Inhibition of hippocampal plasticity in rats performing contrafreeloading for water under repeated administrations of pramipexole

RATIONALE

Compulsive symptoms develop in patients exposed to pramipexole (PPX), a dopaminergic agonist with high selectivity for the D3 receptor. Consistently, we demonstrated that PPX produces an exaggerated increase in contrafreeloading (CFL) for water, a repetitive and highly inflexible behavior that models core aspects of compulsive disorders.

OBJECTIVES

Given the role of the hippocampus in behavioral flexibility, motivational control, and visuospatial working memory, we investigated the role of hippocampus in the expression of PPX-induced CFL. To this aim, rats were subjected to CFL under chronic PPX, and then examined for the electrophysiological, structural, and molecular properties of their hippocampus.

METHODS

We measured long-term potentiation (LTP) at CA1 Schaffer collaterals, dendritic spine density in CA1 pyramidal neurons, and then glutamate release and expression of pre and postsynaptic proteins in hippocampal synaptosomes. The effects of PPX on hippocampal-dependent working memory were assessed through the novel object recognition (NOR) test.

RESULTS

We found that PPX-treated rats showing CFL exhibited a significant decrease in hippocampal LTP and failed to exhibit the expected increase in hippocampal spine density. Glutamate release and PSD-95 expression were decreased, while pSYN expression was increased in hippocampal synaptosomes of PPX-treated rats showing CFL. Despite a general impairment of hippocampal synaptic function, working memory was unaffected by PPX treatment.

CONCLUSIONS

Our findings demonstrate that chronic PPX affects synaptic function in the hippocampus, an area that is critically involved in the expression of flexible, goal-centered behaviors. We suggest that the hippocampus is a promising target in the pharmacotherapy of compulsive disorders.

Are 5-HT3 antagonists effective in obsessive-compulsive disorder? A systematic review of literature

OBJECTIVE

The purpose of this literature database search-based review was to critically consider and evaluate the findings of literature focusing on efficacy and safety of 5-HT3 antagonists in the treatment of obsessive-compulsive disorder (OCD), so as to test whether preclinical data match clinical therapeutic trials.

DESIGN

The PubMed database has been searched for papers on 5-HT3 antagonists and OCD in humans and for animal models of OCD and 5-HT3 receptors.

RESULTS

Of the clinically tested 5-HT3 receptor antagonists, ondansetron has been used to treat OCD in five therapeutic studies, whereas granisetron only in one recent trial. Both showed some efficacy in open studies and superiority to placebo in double-blind studies, along with fair safety. No animal OCD model directly implicated 5-HT3 receptors.

CONCLUSIONS

Overall, results indicate some utility, but the available literature is too scanty to allow for valid conclusions to be drawn. The mismatch between animal models of obsessive-compulsive disorder and clinical data with 5-HT3 antagonists needs more clinical data to ensure that it is not an artefact.

Animal models of obsessive-compulsive disorder: utility and limitations

Obsessive-compulsive disorder (OCD) is a disabling and common neuropsychiatric condition of poorly known etiology. Many attempts have been made in the last few years to develop animal models of OCD with the aim of clarifying the genetic, neurochemical, and neuroanatomical basis of the disorder, as well as of developing novel pharmacological and neurosurgical treatments that may help to improve the prognosis of the illness. The latter goal is particularly important given that around 40% of patients with OCD do not respond to currently available therapies. This article summarizes strengths and limitations of the leading animal models of OCD including genetic, pharmacologically induced, behavioral manipulation-based, and neurodevelopmental models according to their face, construct, and predictive validity. On the basis of this evaluation, we discuss that currently labeled "animal models of OCD" should be regarded not as models of OCD but, rather, as animal models of different psychopathological processes, such as compulsivity, stereotypy, or perseverance, that are present not only in OCD but also in other psychiatric or neurological disorders. Animal models might constitute a challenging approach to study the neural and genetic mechanism of these phenomena from a trans-diagnostic perspective. Animal models are also of particular interest as tools for developing new therapeutic options for OCD, with the greatest convergence focusing on the glutamatergic system, the role of ovarian and related hormones, and the exploration of new potential targets for deep brain stimulation. Finally, future research on neurocognitive deficits associated with OCD through the use of analogous animal tasks could also provide a genuine opportunity to disentangle the complex etiology of the disorder.

Differences in the structure of drinking, cart expression and dopamine turnover between polydipsic and non polydipsic rats in the quinpirole model of psychotic polydipsia

RATIONALE

Dopaminergic D2/D3 agonist quinpirole (QNP) elicits nonregulatory drinking in rats, a model of psychotic polydipsia. Why only a fraction of QNP-treated rats responds to the treatment becoming polydipsic is still unclear.

OBJECTIVES

To unveil possible factors contributing to such variability, we analyzed drinking microstructure in saline and QNP-treated rats, the hypothalamic expression of the cocaine and amphetamine regulated transcript (CART), and the monoaminergic turnover in selected brain areas.

METHODS

Rats were daily treated with saline or QNP 0.5 mg/kg, and their 5-h water intake was measured for five consecutive days. The number of bouts and episodes of licking, and their duration, were also measured. Brain CART expression was measured by in situ hybridization and monoamines turnover by HPLC analysis of tissue extracts. Based on the amount of water ingested during the 5-h session, QNP-treated rats were post hoc grouped in polydipsic (PD) and in nonpolydipsic (NPD) rats, and the results compared accordingly.

RESULTS

The number of drinking bouts and episodes increased in PD rats, while NPD rats behaved as the controls. CART expression decreased in the arcuate nucleus of the hypothalamus of the PD rats. In contrast, both PD and NPD rats showed a reduction of DA turnover in both ventral tegmental area (VTA) and nucleus accumbens (NAcc). No difference was detected in the turnover of 5HT and NA.

CONCLUSIONS

Microstructure analysis confirms that QNP acts on the appetitive component of drinking behavior, making it compulsive. CART expression reduction in response to dopaminergic hyperstimulation might sustain excessive drinking in PD rats.

Spatial reversal learning in chronically sensitized rats and in undrugged sensitized rats with dopamine d2-like receptor agonist quinpirole

Dopamine plays a role in generating flexible adaptive responses in changing environments. Chronic administration of D2-like agonist quinpirole (QNP) induces behavioral sensitization and stereotypical behaviors reminiscent of obsessive–compulsive disorder (OCD). Some of these symptoms persist even after QNP discontinuation. In QNP-sensitization, perseverative behavior has often been implicated. To test the effect of QNP-sensitization on reversal learning and its association with perseveration we selected an aversively motivated hippocampus-dependent task, active place avoidance on a Carousel. Performance was measured as the number of entrances into a to-be-avoided sector (errors). We tested separately QNP-sensitized rats in QNP-drugged and QNP-undrugged state in acquisition and reversal tasks on the Carousel. In acquisition learning there were no significant differences between groups and their respective controls. In reversal, QNP-sensitized drugged rats showed a robust but transient increase in number of errors compared to controls. QNP-sensitized rats in an undrugged state were not overtly different from the control animals but displayed an altered learning manifested by more errors at the beginning compensated by quicker learning in the second session compared to control animals. Importantly, performance was not associated with perseveration in neither QNP-sensitized drugged nor QNP-sensitized undrugged animals. The present results show that chronic QNP treatment induces robust reversal learning deficit only when the substance is continuously administered, and suggest that QNP animal model of OCD is also feasible model of cognitive alterations in this disorder.

Animal models of obsessive-compulsive spectrum disorders

Obsessive-compulsive disorder (OCD) and related conditions (trichotillomania, pathological skin-picking, pathological nail-biting) are common and disabling. Current treatment approaches fail to help a significant proportion of patients. Multiple tiers of evidence link these conditions with underlying dysregulation of particular cortico-subcortical circuitry and monoamine systems, which represent targets for treatment. Animal models designed to capture aspects of these conditions are critical for several reasons. First, they help in furthering our understanding of neuroanatomical and neurochemical underpinnings of the obsessive-compulsive (OC) spectrum. Second, they help to account for the brain mechanisms by which existing treatments (pharmacotherapy, psychotherapy, deep brain stimulation) exert their beneficial effects on patients. Third, they inform the search for novel treatments. This article provides a critique of key animal models for selected OC spectrum disorders, beginning with initial work relating to anxiety, but moving on to recent developments in domains of genetic, pharmacological, cognitive, and ethological models. We find that there is a burgeoning literature in these areas with important ramifications, which are considered, along with salient future lines of research.

Effects of the 5HT2C antagonist SB242084 on the pramipexole-induced potentiation of water contrafreeloading, a putative animal model of compulsive behavior

RATIONALE

In rats, quinpirole, a dopaminergic D2/D3 receptor agonist, elicits both hyperdipsia and water "contrafreeloading" (CFL), a putative model of compulsivity. The role of D3 receptors in this effect remains unclear. Clomipramine (CIM) was found to contrast both hyperdipsia and CFL, but the role of serotonin in this effect requires further investigation.

OBJECTIVES

We studied the effects of the preferential D3 agonist pramipexole (PPX) in both models. Furthermore, we tested the sensitivity of PPX-induced CFL to CIM and to the 5HT2c antagonist SB242084.

METHODS

In experiment 1, drinking was measured at 2 and 5 h after eight daily injections of PPX (0 to 1.0 mg/kg intraperitoneally). In the CFL study, every other third lever press, the rat was reinforced by the delivery of water. On days 1-6, water was only available upon lever pressing. On days 7-15, choice between response-contingent and free access was provided. PPX doses as in the experiment 1 were given. In two further experiments, PPX (0.5 mg/kg) was administered alone or in combination with CIM (5 or 10 mg/kg) or SB242084 (0.3 or 1.0 mg/kg).

RESULTS

PPX did not produce hyperdipsia but enhanced spontaneous CFL. SB242084 attenuated PPX-induced CFL more effectively than CIM, restoring the preference for free access to water.

CONCLUSIONS

CFL, but not polydipsia, was induced by preferential D3 activation, an effect prevented by 5HT2c receptor blockade. Since PPX interferes with decision making and 5HT2c receptor supersensitivity is involved in the expression of compulsive behaviors, this study supports the compulsive nature of dopaminergic-induced CFL.

Increased drinking after intra-striatal injection of the dopamine D2/D3 receptor agonist quinpirole in the rat

RATIONALE

Dopamine D2 receptor hyperactivity has been implicated in the development of psychogenic polydipsia in schizophrenic patients. Repeated treatment with dopamine agonists, including the D2/D3 agonist quinpirole, has been shown to induce hyperdipsia in a number of animal models. Despite these observations, obtained with systemic administrations, little attempt has been made to investigate where in the brain dopamine agonists act to induce hyperdipsia.

OBJECTIVE

The present study investigates the effects of repeated intra-caudate infusions of quinpirole on the intake of water by rats tested under free-drinking conditions.

MATERIALS AND METHODS

Rats with bilateral cannulae placed into the anterior, central or posterior caudate received quinpirole microinfusions (1 μg/side) for five consecutive days in their home cage. Water intake was measured 15 and 60 min after the treatment.

RESULTS

When injected in the central caudate, quinpirole increased water intake, and this effect progressively increased over sessions, indicating the development of sensitization. When injected in the posterior caudate, the dipsogenic effect of quinpirole was less intense and did not undergo sensitization. The infusion of quinpirole in the anterior caudate did not affect drinking.

CONCLUSION

The present study shows that caudate D2/3 receptors play an important role in the development of quinpirole-induced hyperdipsia, an animal model of psychotic polydipsia.

Dopamine agonists and pathologic behaviors

The dopamine agonists ropinirole and pramipexole exhibit highly specific affinity for the cerebral dopamine D3 receptor. Use of these medications in Parkinson's disease has been complicated by the emergence of pathologic behavioral patterns such as hypersexuality, pathologic gambling, excessive hobbying, and other circumscribed obsessive-compulsive disorders of impulse control in people having no history of such disorders. These behavioral changes typically remit following discontinuation of the medication, further demonstrating a causal relationship. Expression of the D3 receptor is particularly rich within the limbic system, where it plays an important role in modulating the physiologic and emotional experience of novelty, reward, and risk assessment. Converging neuroanatomical, physiological, and behavioral science data suggest the high D3 affinity of these medications as the basis for these behavioral changes. These observations suggest the D3 receptor as a therapeutic target for obsessive-compulsive disorder and substance abuse, and improved understanding of D3 receptor function may aid drug design of future atypical antipsychotics.