Variability of drug self-administration in rats

• Published in: Psychopharmacologia Vol. 167; no. 1; pp. 9 - 19
• Main Authors: Panlilio, Leigh V., Katz, Jonathan L., Pickens, Roy W., Schindler, Charles W.
• Format: Journal Article
• Language: English
• Published: Berlin Springer 01.04.2003; Springer Nature B.V
• Subjects: Analgesics, Opioid - administration & dosage; Analgesics, Opioid - pharmacology; Animals; Biological and medical sciences; Cocaine - administration & dosage; Cocaine - pharmacology; Conditioning, Operant; Dose-Response Relationship, Drug; Drug addictions; Food; Male; Medical sciences; Piperidines - administration & dosage; Piperidines - pharmacology; Rats; Rats, Sprague-Dawley; Reaction Time; Reinforcement Schedule; Self Administration; Toxicology; Agonist; Intravenous administration; Rat; Psychotropic; μ Opioid receptor; Opiates; Self administration; Narcotic analgesic; Remifentanil; Dose activity relation; Learning; Ester; Acquisition process; Dependence; Reinforcement; Satiety; Drug of abuse; Food; CNS stimulant; Rodentia; Instrumental conditioning; Vertebrata; Mammalia; Animal; Interindividual comparison; Titration Regulation; Cocaine; Comparative study
• ISSN: 0033-3158; 1432-2072
• DOI: 10.1007/s00213-002-1366-x

Although temporal patterns of drug self-administration in animals are known to be highly regular, this regularity has rarely been quantified or systematically compared across reinforcers. Over a range of unit doses, this study assessed: (1) the within-subject variability of inter-infusion intervals (latencies); (2) the estimated whole-body drug level at the time of self-infusion; (3) the within-subject variability of these drug levels; and (4) the statistical dependence between successive latencies, to determine whether regularity is maintained by compensatory, moment-to-moment adjustment of latencies. Rats were trained with cocaine (10-1000 microg/kg per infusion, IV), remifentanil (an ultra-short acting opioid; 0.25-32 microg/kg per infusion, IV), or food (20-180 mg/delivery). Within subjects, latencies were most consistent from infusion to infusion at unit doses on the descending limb of the dose-response curve. However, the drug level at the time an infusion was initiated was actually least consistent at these doses. Sequential latencies showed only a weak autocorrelation for both drugs. These results suggest that highly consistent response patterns are not simply a product of precise titration of drug levels. The weak autocorrelation between sequential latencies suggests that temporal regularity of responding is not maintained through compensatory adjustments of post-infusion pauses.