A Phaseolus vulgaris Extract Reduces Cue-Induced Reinstatement of Chocolate Seeking in Rats

Irene Lorrai,Mauro A M Carai,Gian Luigi Gessa,Giancarlo Colombo,Paolo Morazzoni,Valentina Piga,Paola Maccioni,Antonella Riva

doi:10.3389/fphar.2016.00109

Abstract

Previous evidence has suggested that treatment with a standardized dry extract of Phaseolus vulgaris reduced intake and operant self-administration of highly palatable foods and fluids in rats and mice. The present study was designed to assess whether such extract was also effective in reducing seeking behavior for a highly hedonic chocolate-flavored beverage, using a “reinstatement” procedure adopted from the drug addiction research field and modeling relapse behavior. Rats were initially trained to lever-respond for the chocolate-flavored beverage under the Fixed Ratio (FR) 10 schedule of reinforcement. Subsequently, rats were exposed to an extinction responding phase, during which lever-responding – being unreinforced – diminished progressively up to extinction. Lever-responding was then powerfully reinstated by the non-contingent presentation of a complex of gustatory, olfactory, auditory, and visual stimuli previously associated to the availability of the chocolate-flavored beverage. Acute, intragastric administration of P. vulgaris dry extract (100 and 500 mg/kg) reduced lever-responding by 40–45%, in comparison to vehicle condition. These results indicate the ability of P. vulgaris dry extract to reduce seeking behavior for a highly palatable nourishment in an experimental model of relapse into disordered eating of palatable foods. The unavailability of the chocolate-flavored beverage in the reinstatement session tends to exclude that the observed effect of the P. vulgaris dry extract was secondary to any inhibition of carbohydrate metabolism; conversely, it is the likely consequence on a central action on the rewarding and hedonic properties of food.

Highlights

The Phaseolus vulgaris genus includes all species of legume seeds typically referred to as common beans
We employed (i) the same, standardized dry extract of P. vulgaris tested in all previous studies with different palatable nourishments (Carai et al, 2009; Fantini et al, 2009; Maccioni et al, 2010; Loi et al, 2013) and (ii) a chocolateflavored beverage possessing high hedonic, reinforcing, and motivational properties in rats; we adapted to the chocolate-flavored beverage an experimental procedure, named “reinstatement of seeking behavior,” largely used in the drug addiction field to model relapse episodes and loss of control over substances of abuse and, in much fewer instances, palatable foods (Martín-García et al, 2011; Calu et al, 2014)
Rats were trained to lever-respond for the chocolate-flavored beverage [5% (w/v) Nesquik R chocolate powder in water] under the Fixed Ratio (FR) 10 schedule of reinforcement in daily 60 min self-administration sessions

Summary

Introduction

The Phaseolus vulgaris genus includes all species of legume seeds typically referred to as common beans. With the aim of characterizing more in-depth the pharmacological profile of P. vulgaris extracts, the present study was designed to investigate the effect of a P. vulgaris extract on seeking behavior for a highly palatable food in rats To this end, we employed (i) the same, standardized dry extract of P. vulgaris tested in all previous studies with different palatable nourishments (Carai et al, 2009; Fantini et al, 2009; Maccioni et al, 2010; Loi et al, 2013) and (ii) a chocolateflavored beverage possessing high hedonic, reinforcing, and motivational properties in rats (see Maccioni and Colombo, 2016); we adapted to the chocolate-flavored beverage an experimental procedure, named “reinstatement of seeking behavior,” largely used in the drug addiction field to model relapse episodes and loss of control over substances of abuse (see Markou et al, 1993; Bossert et al, 2013) and, in much fewer instances, palatable foods (Martín-García et al, 2011; Calu et al, 2014). Concurrence of these stimuli or events is expected to trigger an intense reinstatement of lever-responding (still unreinforced), proposed to mimic human craving and seeking for the specific substance (see Markou et al, 1993; Bossert et al, 2013; Calu et al, 2014)

Methods

Results

Discussion

Conclusion