Sucrose Preference and Novelty-Induced Hypophagia Tests in Rats using an Automated Food Intake Monitoring System

Summary

Presented here is a protocol to study depression-like and anhedonic behavior in rats. It combines two well-established behavioral methods, the sucrose preference and novelty-induced hypophagia tests, with an automated food and liquid intake monitoring system, to indirectly investigate rodent behavior using surrogate parameters.

Abstract

The prevalence and incidence of depressive disorders are rising worldwide, affecting about 322 million individuals, underlining the need for behavioral studies in animal models. In this protocol, to study depression-like and anhedonic behavior in rats, the established sucrose preference and novelty-induced hypophagia tests are combined with an automated food and liquid intake monitoring system. Prior to testing, in the sucrose preference paradigm, male rats are trained for at least 2 days to consume a sucrose solution in addition to tap water. During the test, rats are again exposed to water and sucrose solution. Consumption is registered every second by the automated system. The ratio of sucrose to total water intake (sucrose preference ratio) is a surrogate parameter for anhedonia. In the novelty-induced hypophagia test, male rats undergo a training period in which they are exposed to a palatable snack. During training, rodents show a stable baseline snack intake. On test day, the animals are transferred from home cages into a fresh, empty cage representing a novel unknown environment with access to the known palatable snack. The automated system records the total intake and its underlying microstructure (e.g., latency to approaching the snack), providing insight into anhedonic and anxious behaviors. The combination of these paradigms with an automated measuring system provides more detailed information, along with higher accuracy by reducing measuring errors. However, the tests use surrogate parameters and only depict depression and anhedonia in an indirect manner.

Introduction

On average, 4.4% of the world’s population is affected by depression. These account for 322 million people worldwide, an 18% increase compared to ten years ago¹. According to estimates by the World Health Organization, depression will be second in the ranking of Disability Adjusted Life Years in 2020². To address the rising prevalence of affective disorders and establish new interventional strategies, it is necessary to further study this behavior. Prior and in addition to examination in humans, animal studies are necessary.

Several models have been established to study components of dep....

Protocol

Animal care and experimental procedures followed the specific institutional ethics guidelines and was approved by the state authority for animal research.

1. Operation of the automated monitoring system

NOTE: When operating the automated monitoring system, it is crucial to document every action in the comment box included in the software immediately prior to the action. The description should be typed into the comment box, and by pressing Save, it is .......

Discussion

The sucrose preference and novelty-induced hypophagia tests are two established techniques for evaluating anhedonia in rats. Their combination with the automated food intake monitoring system allows for more detailed analysis in undisturbed rats and reduces erroneous measurement.

The incidence of errors is reduced by different approaches. First, to address the error occurring due to spillage, the gap between the food hopper and gate allows crumbs generated during gnawing to fall onto the integ.......

Materials

Name	Company	Catalog Number	Comments
Assembly LH Cage Mount - RAT-FOOD - includes Stainless cage mount, hopper, blocker, coupling	Research Diets, Inc., Jules Lane, New Brunswick, NJ, USA	BCMPRF01
Assembly LH Cage Mount unplugged - RAT - FOOD includes stainless steel cage mount, hopper, blocker, unplugged adapter, coupling	Research Diets, Inc., Jules Lane, New Brunswick, NJ, USA	BCMUPRF01
cage w/ 2 openings - RAT - costum modified cage - includes cage top and standard water bottle	Research Diets, Inc., Jules Lane, New Brunswick, NJ, USA	BCR02	single housing
Data collection Laptop Windows - Configured w/ BioDAQ Software	Research Diets, Inc., Jules Lane, New Brunswick, NJ, USA	BLT003
enrichment (plastic tubes, gnawing wood)			distributed by the animal facility
HoneyMaid Graham Cracker Crumbs	Nabisco, East Hanover, NJ, USA	ASIN: B01COWTA98	palatable snack for NIH test
low vibration polymer rack	Research Diets, Inc., Jules Lane, New Brunswick, NJ, USA	BRACKR
male Sprague Dawley rats	Envigo	Order Code: 002
Model #2210 32x Port BioDAQ Central Controller - includes cables, and calibration kit	Research Diets, Inc., Jules Lane, New Brunswick, NJ, USA	BCC32_03
Peripheral sensor Controller - includes cable	Research Diets, Inc., Jules Lane, New Brunswick, NJ, USA	BPSC01
SigmaStat 3.1	Systat Software, San Jose, CA, USA		statistical analysis
Stainless steel blocker	Research Diets, Inc., Jules Lane, New Brunswick, NJ, USA	BBLKR
standard rodent diet with 10 kcal% fat	Research Diets, Inc., Jules Lane, New Brunswick, NJ, USA	D12450B
sucrose powder	Roth	4621.1	for SPT