Marco Venniro1, Anna Mutti2, Cristiano Chiamulera2. 1. Neuropsychopharmacology Laboratory, Section of Pharmacology, Department of Public Health and Community Medicine, University of Verona, Policlinico Borgo Roma, P.le Scuro 10, 37134, Verona, Italy. venniro.marco@nih.gov. 2. Neuropsychopharmacology Laboratory, Section of Pharmacology, Department of Public Health and Community Medicine, University of Verona, Policlinico Borgo Roma, P.le Scuro 10, 37134, Verona, Italy.
Abstract
BACKGROUND: Recreational ketamine use may be modulated by factors such as ketamine infusion patterns, associated conditioned stimuli and spatial-temporal contexts. Our aim was to study the pharmacological and non-pharmacological factors that regulate the acquisition of ketamine use. METHODS: In experiment 1, four groups of male rats were trained to self-administer ketamine during nine 1-h daily sessions, under four reinforcement schedules: i) pre-session ketamine priming (Priming-[KET]), ii) conditioned stimulus (CS) paired to the ketamine infusions ([KET + CS]), iii) neither priming nor CS ([KET]), iv) combination of both (Priming-[KET + CS]). In experiment 2, two groups of male rats were trained to self-administer ketamine during nine 1-h daily or weekly sessions, under the Priming-[KET + CS] schedule. Lever pressing was then extinguished by saline substitution for ketamine infusion. Afterwards, ketamine was made available again upon responding under the same schedule. RESULTS: The Priming-[KET + CS] schedule of reinforcement showed a significant increase in the number of ketamine reinforcements and a significant discrimination between active vs. inactive levers. The same schedule allowed the establishment of ketamine self-administration on a weekly basis. During the extinction phase, rate of responding significantly dropped in both weekly and daily groups although it was twofold longer in the former, which showed a lack of reacquisition. CONCLUSIONS: Both pre-session ketamine priming and a conditioned stimulus paired to the ketamine infusions are required for the acquisition of ketamine self-administration. The longer extinction and the lack of reacquisition in the weekly group could be due to changes in temporal context that might affect the conditioning process.
BACKGROUND: Recreational ketamine use may be modulated by factors such as ketamine infusion patterns, associated conditioned stimuli and spatial-temporal contexts. Our aim was to study the pharmacological and non-pharmacological factors that regulate the acquisition of ketamine use. METHODS: In experiment 1, four groups of male rats were trained to self-administer ketamine during nine 1-h daily sessions, under four reinforcement schedules: i) pre-session ketamine priming (Priming-[KET]), ii) conditioned stimulus (CS) paired to the ketamine infusions ([KET + CS]), iii) neither priming nor CS ([KET]), iv) combination of both (Priming-[KET + CS]). In experiment 2, two groups of male rats were trained to self-administer ketamine during nine 1-h daily or weekly sessions, under the Priming-[KET + CS] schedule. Lever pressing was then extinguished by saline substitution for ketamine infusion. Afterwards, ketamine was made available again upon responding under the same schedule. RESULTS: The Priming-[KET + CS] schedule of reinforcement showed a significant increase in the number of ketamine reinforcements and a significant discrimination between active vs. inactive levers. The same schedule allowed the establishment of ketamine self-administration on a weekly basis. During the extinction phase, rate of responding significantly dropped in both weekly and daily groups although it was twofold longer in the former, which showed a lack of reacquisition. CONCLUSIONS: Both pre-session ketamine priming and a conditioned stimulus paired to the ketamine infusions are required for the acquisition of ketamine self-administration. The longer extinction and the lack of reacquisition in the weekly group could be due to changes in temporal context that might affect the conditioning process.
Authors: A R Caggiula; E C Donny; A R White; N Chaudhri; S Booth; M A Gharib; A Hoffman; K A Perkins; A F Sved Journal: Pharmacol Biochem Behav Date: 2001-12 Impact factor: 3.533
Authors: Nadia Chaudhri; Anthony R Caggiula; Eric C Donny; Sheri Booth; Maysa Gharib; Laure Craven; Matthew I Palmatier; Xiu Liu; Alan F Sved Journal: Psychopharmacology (Berl) Date: 2006-07-18 Impact factor: 4.530