Format

Send to

Choose Destination
Psychopharmacology (Berl). 2010 Oct;212(3):369-78. doi: 10.1007/s00213-010-1966-9. Epub 2010 Aug 5.

Reinforcer-dependent enhancement of operant responding in opioid-withdrawn rats.

Author information

1
Department of Psychiatry, College of Physicians and Surgeons, Columbia University, New York State Psychiatric Institute, Substance Use Research Center, 1051 Riverside Dr, New York, NY 10032, USA. zc2160@columbia.edu

Abstract

RATIONALE AND OBJECTIVE:

Opioid withdrawal increases the reinforcing effectiveness of the μ-opioid agonist remifentanil in rodents. The current study explored the selectivity of this effect by assessing operant behavior maintained by drug and non-drug reinforcers, remifentanil, cocaine, a palatable liquid food, and standard food pellets, as a function of opioid dependence and withdrawal.

MATERIALS AND METHODS:

Operant responding exhibited by nondependent, morphine-naïve groups was compared with responding exhibited by morphine-dependent and withdrawn groups. Dependence was established using a noncontingent morphine dosing procedure that has been previously verified to maintain dependence while allowing for daily behavioral observation during a withdrawn state. Behavior maintained by remifentanil (0.10-10.0 μg/kg/infusion), cocaine (0.032-1.0 mg/kg/infusion), a palatable liquid food reinforcer (3.2-100.0% Vanilla Ensure® and water), or food pellets was assessed in dependent and nondependent groups.

RESULTS:

Morphine withdrawal enhanced remifentanil self-administration, resulting in an upward and rightward shift of the descending limb of the dose-response curve, and increased operant responding for both food reinforcers. However, opioid withdrawal did not affect cocaine self-administration, nor did it affect responding for water.

CONCLUSIONS:

Enhanced operant responding observed under opioid-dependent and withdrawn conditions, while selective, is generalized to some nonopioid reinforcers.

PMID:
20686752
PMCID:
PMC3001287
DOI:
10.1007/s00213-010-1966-9
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Springer Icon for PubMed Central
Loading ...
Support Center