A Procedure to Study Stress-Induced Relapse of Heroin Seeking after Punishment-Imposed Abstinence

Summary

A procedure that demonstrates a robust acute food deprivation-induced relapse to heroin seeking after punishment-imposed abstinence is described. A punishment-imposed abstinence model was successfully implemented using the seek and take chain schedule for heroin self-administration. Heroin-seeking tests are then performed following 24 h of food-deprivation stress.

Abstract

The punishment-imposed abstinence procedure models the self-imposed abstinence that humans initiate due to the adverse consequences associated with drug-taking. This model has been implemented in experiments using different types of substances of abuse such as methamphetamine, cocaine, and alcohol. However, punishment-induced abstinence in heroin-trained animals has not been demonstrated. Furthermore, acute stress is a key trigger for relapse in humans and animal models. It was previously demonstrated that acute food deprivation robustly induced reinstatement of extinguished cocaine and heroin seeking. The procedure described here can be used to assess the effects of acute stress exposure on heroin seeking after punishment-imposed abstinence. A total of 8 rats were implanted with chronic intravenous (i.v.) catheters and trained to self-administer heroin (0.1 mg/kg/infusion) for 18 days under a seek-take chained schedule. Completing the seek link gave access to the take lever, which was paired with a heroin infusion. The seek lever was programmed with a variable interval 60 schedule of reinforcement (VI60), and the take lever was programmed with a fixed-ratio 1 reinforcement schedule (FR1). Following self-administration training, a mild foot shock was delivered on 30% of the completed seek links instead of the extension of the take lever. Footshock intensity was increased by 0.1 mA per daily session from 0.2 mA to 1.0 mA. Heroin-seeking tests were performed after 24 h of food deprivation (FD) or sated conditions. Rats under acute food deprivation condition robustly increased heroin seeking after punishment-imposed abstinence.

Introduction

Relapse is the most challenging problem in the treatment of drug use^1,2. However, only a handful of pharmacological treatments are approved to help avoid relapse in humans³. The opioid epidemic that North America is currently facing is a striking example of it, and it demands considering different approaches on animal models of relapse to opioids.

Acute stress has been shown to be a key trigger to relapse in humans⁴. One environmental stressor that is often associated with drug addiction is food deprivation. Drug ....

Protocol

All rats are treated according to the guidelines of the Canadian Council on Animal Care. Approval for all the experimental procedures was granted by the Concordia University Animal Research Ethics Committee.

1. Animals

1. Acquire Long Evans rats weighing 275-300 g (males) or 225-250 g (females). Double house rats in standard plastic cages with corncob bedding and shredded paper until surgery.
2. Keep the rats on a reversed light-dark cycle (lights off at 9:30 AM, light on at 9:30 PM).
3. Allow unlimited access to food and water, except during the food-deprivation test. Use regular rat chow (20.9% prot....

Results

Male rats demonstrated an increase in seek lever presses as the schedule of reinforcement increased over the training days, and a reliable, consistent number of heroin infusions over training days (Figure 1). During punishment, rats decreased the number of seek lever presses and infusions with the increase of footshock intensity over 8 punishment days (Figure 2). Food-deprivation condition significantly increased heroin seeking after punishment-imposed abstinenc.......

Discussion

There are two important demonstrations in this paper. First, the validation of the punishment-imposed abstinence using the seek and take chain with heroin. Second, it was demonstrated that stress-induced relapse could be observed in a punishment-imposed abstinence procedure. These are important demonstrations because (i) The punishment-induced abstinence procedure more closely mimics the human condition as it results in voluntary abstinence, i.e., not due to extinction of drug-seeking or forced removal from the drug-taki.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Anafen Injection 100 mg/mL Vial/50 mL	MERIAL Canada, Inc.	1938126	anti-inflammatory drug
Balance arm	Coulbourn Instruments	H29-01
Cannulae (22 G, 5-up)	Plastics One	C313G-5up
Environment connection board & Linc cable	Coulbourn Instruments	H03-04
Fixed speed infusion pump (3.3 RPM)	Coulbourn Instruments	A73-01-3.3
GE Marine Silicon	GE	SE-1134
Graphic State Notation 3	Coulbourn Instruments	GS3	Software
Habitest universal Linc	Coulbourn Instruments	H02-08
Heroin HCl	National Institute for Drug Abuse, Research Triangle Park, NC, USA
House light-Rat	Coulbourn Instruments	H11-01R
Isofluorane USP 99.9% Vial/250 mL	Fresenius Kabi Canada Ltd	2237518
Liquid Swivels, Plastic, 22 G	Lomir Biomedical, Inc.	RSP1
Rat test cage	Coulbourn Instruments	H10-11R-TC	Operant conditioning chambers
Retractable lever-Rat	Coulbourn Instruments	H23-17RA
Silastic tubing (ID 0.02, OD 0.037)	Fisher Scientific (Canada)	1118915A
Single high-bright cue-Rat	Coulbourn Instruments	H11-03R
Sound attenuation boxes	Concordia University	Home made
Stainless steal grid floor	Coulbourn Instruments	H10-11R-TC-SF
System controller 2	Coulbourn Instruments	SYS CTRL 2
System power base	Coulbourn Instruments	H01-01
Tone module 2.9 KHz	Coulbourn Instruments	H12-02R-2.9
Tygon tubing (ID 0.02, OD 0.060)	VWR	63018-044