Chemical afferent vagal axotomy blocks re-intake after partial withdrawal of gastric food contents

Abstract

Objectives: The aim of this study was to investigate the biological process by which animals regulate meal size. An experimental procedure for its study is to examine food re-intake after partial withdrawal of gastric food contents.

Methods: The aim of the present experiments was to investigate the role of vagal afferents in food re-intake after perivagal administration of capsaicin, a neurotoxin that specifically damages weakly myelinated or unmyelinated vagal sensory axons.

Results: In experiment 1, capsaicin-treated animals initially consumed higher amounts of food in comparison to controls (in first 24 hours) but their excess intake was compensated for in subsequent daily satiation tests. However, capsaicin treatment impaired the common short-term re-intake behavior observed in control rats after partial removal of gastric food nutrients, and the lesioned animals consumed significantly less food than had been withdrawn after completion of the initial meal; moreover, in this deficit condition, no counteraction was observed in subsequent repeated tests. This behavioral disturbance cannot be attributed to an indirect effect of capsaicin on gastric emptying volume, because the stomach contents were similar in both groups (Experiment 2).

Discussion: These findings are discussed in terms of the critical role played by vagal afferents in rapid visceral adjustments related to short-term food intake, as also observed in other gastrointestinal regulatory behaviors that require immediate processing of visceral sensory information.

Keywords:

• Satiation
• Meal size
• Stomach weight
• Gastric emptying
• Capsaicin
• Rapid visceral adjustments

Acknowledgements

We are grateful to Richard Davies for his assistance with the English version of this paper.

Disclaimer statements

Contributors MAZ, FM, and AP conceived the study; MAZ and FM performed the experiments; MAZ and AP analyzed the data and wrote the paper.

Funding This study was supported in part by the University of Granada and Spanish Ministry of Education and Culture (Nacional R+D Plan: SEJ/FEDER2007-61839 and PSI2010-17400).

Conflicts of interest The authors declare no conflict of interest.

Ethics approval All experimental procedures took place during light periods and were conducted in accordance with the Animal Care and Use Guidelines established by European Community Council Directive 86/609/CEE and Spanish Royal Law 223/1988.