"Himalayan Bridge": A New Unstable Suspended Bridge to Investigate Rodents' Venturesome Behavior.

Fabiana Festucci,Maurizio Oggiano,Giovanni Laviola,Anna Parvopassu,Giuseppe Curcio,Walter Adriani,Marco Bortolato,Clelia Buccheri

doi:10.3389/fnbeh.2021.637074

Fabiana Festucci, Maurizio Oggiano + Show 6 more

Open Access

https://doi.org/10.3389/fnbeh.2021.637074

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Abstract

While both risk-taking and avoidant behaviors are necessary for survival, their imbalanced expression can lead to impulse-control and anxiety disorders, respectively. In laboratory rodents, the conflict between risk proneness and anxiety can be studied by using their innate fear of heights. To explore this aspect in detail and investigate venturesome behavior, here we used a “Himalayan Bridge,” a rat-adapted version of the suspended wire bridge protocol originally developed for mice. The apparatus is composed of two elevated scaffolds connected by bridges of different lengths and stability at 1 m above a foam rubber-covered floor. Rats were allowed to cross the bridge to reach food, and crossings, pawslips, turnabouts, and latencies to cross were measured. Given the link between risky behavior and adolescence, we used this apparatus to investigate the different responses elicited by a homecage mate on the adolescent development of risk-taking behavior. Thus, 24 wild-type (WT) subjects were divided into three different housing groups: WT rats grown up with WT adult rats; control WT adolescent rats (grown up with WT adolescents), which showed a proclivity to risk; and WT rats grown up with an adult rat harboring a truncated mutation for their dopamine transporter (DAT). This latter group exhibited risk-averse responses reminiscent of lower venturesomeness. Our results suggest that the Himalayan Bridge may be useful to investigate risk perception and seeking; thus, it should be included in the behavioral phenotyping of rat models of psychiatric disorders and cognitive dysfunctions.

Highlights

The decision-making process that leads individuals to choose between different beneficial and harmful options is at the heart of everyday life
The fact that the fear of heights is rapidly acquired during initial exposure to the apparatus suggests that there is a genetic, innate predisposition to develop this fear
Conditioned fear, based on associating cues/contexts to unescapable aversive stimuli, or instrumental punishment, based on negative reinforcement to cancel an unwanted action with its punishment, has been used to model phobia; simple exposure to frights or innately scary situations has not yet been used to prove useful animal models of phobia

Summary

Introduction

The decision-making process that leads individuals to choose between different beneficial and harmful options is at the heart of everyday life. Conditioned fear, based on associating cues/contexts to unescapable aversive stimuli, or instrumental punishment, based on negative reinforcement to cancel an unwanted action with its punishment, has been used to model phobia; simple exposure to frights or innately scary situations has not yet been used to prove useful animal models of phobia. This rapidly acquired fear of heights using a naturalistic test situation may prove more useful (Klein, 1980). This feeling of danger causes excessive and maladaptive avoidance that contributes to the development and maintenance of anxiety disorders and prevents the extinction of fearful responses in humans (Craske et al, 2009; Lovibond et al, 2009) and rodents (Muigg et al, 2008)

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