Schedule-Induced Polydipsia: Searching for the Endophenotype of Compulsive Behavior

Ana Sánchez-Kuhn,Sergio García-Martín,Olga Vilches,Margarita Moreno,Pilar Flores,Ana Merchán

doi:10.4236/wjns.2014.43029

Abstract

The development of excessive and persistent drinking under intermittent food-reinforcement schedules, known Schedule-induced polydipsia (SIP), has been proposed as a successful animal model to study compulsive behaviors. On the last decade, we have been working in our laboratory on the stratification of the compulsive rats on SIP in order to know whether differences in the acquisition of compulsive drinking behavior could predict alterations in other behavioral measures as well as in the neurochemical function typically associated with compulsive spectrum disorders. The aim of this review is to collate the main findings relevant to the characterization and use of the high compulsive drinking rats (HD) in SIP as a possible compulsive endophenotype. The review of the genetic, behavioral and neurochemical differences found in the selection allows us to conclude that HD rats could be a valid model for studying the compulsive phenotype and modelling psychopathology common to a variety of compulsivity spectrum disorders such as obsessivecompulsive disorder (OCD), schizophrenia and alcohol abuse.

Highlights

Compulsivity represents the performance of repetitive and functionally impairing overt or covert behavior without adaptive function, performed in a habitual or stereotyped fashion, either according to rigid rules or as a means of avoiding perceived negative consequences [1]
After schedule-induced polydipsia (SIP) acquisition high compulsive drinking rats (HD) and low drinkers (LD) rats have been tested in different procedures and tasks to assess behaviors and behavioral traits, such as novelty reactivity, anxiety or deficit in inhibitory control related to symptomatology and vulnerability to compulsive spectrum disorders
Because of its characteristics of excessiveness and persistence SIP has been proposed as a successful model to study those neuropsychiatric disorders characterized by the presence of compulsive behavior such as: obsessive-compulsive disorder (OCD), schizophrenia, and alcohol abuse [28]

Summary

Introduction

Compulsivity represents the performance of repetitive and functionally impairing overt or covert behavior without adaptive function, performed in a habitual or stereotyped fashion, either according to rigid rules or as a means of avoiding perceived negative consequences [1]. An excessive non-regulatory drinking, non-related to homeostatic needs or a physiological cause, has been observed in humans among different psychiatric disorders sharing impulsive-compulsive symtomatology such as OCDs, schizophrenia and ADHD [12]-[15]. Other behaviors have been shown to be functionally similar to schedule-induced polydipsia, including aggression [20], excessive running [21], induced stereotypy [22] and pica [23] Different factors, such as the state of food deprivation or the inter-food interval length influence the SIP acquisition and expression [16] [18] [24] [25] data from our laboratory have shown that the optimal Fixed Time (FT) intervals for inducing a high rate of drinking are FT-30s [26] and FT-60s [27]. To achieve that objective we review the genetic, behavioral and neurochemical differences found by the stratification of rats according to individual differences in the acquisition of compulsive drinking on SIP

Genetic Differences

Neurochemical Function in Compulsive SIP Rats

Conclusions