Water deprivation-induced oral self-administration of cocaine in the Lewis rat: evidence for locomotor effects but not reinforcement.
Oral cocaine self-administration was studied in water-deprived Lewis rats. Liquid was available to rats only during daily 90-min sessions, in chambers equipped with spouts that delivered precise volumes of liquid following completion of lever-press responses. Blocks of training and testing sessions were alternately carried out during which increasing cocaine concentrations were presented: 0.0, 0.0125, 0.025, 0.05, 0.1, 0.2, 0.282, and 0.4 mg/ml. Although high cocaine intakes (23.3-33.0 mg/kg) were obtained, neither avoidance nor preference for cocaine developed. Subsequently, fixed-ratio size was increased, and then distinctive stimulus lights were correlated with each liquid. One rat showed a preference for water following these changes, but two rats continued to show no preference. To determine if the amounts of cocaine self-administered had behavioral effects, locomotor activity tests were run immediately following self-administration sessions. Locomotor activity was substantially higher following cocaine self-administration than following water self-administration. These results demonstrate that the cocaine intakes reached under the present conditions did produce locomotor, but not reinforcing, effects.
Bell
S M
SM
Department of Psychiatry and Behavioral Sciences, University of Texas Health Science Center, Houston 77030-3497.
Macenski
M J
MJ
Silverman
P B
PB
Meisch
R A
RA
D000818:Animals; D003042:Cocaine / Q000008:administration & dosage / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D051381:Rats; D011917:Rats, Inbred Lew; D012055:Reinforcement Schedule; D012054:Reinforcement, Psychology; D012646:Self Administration; D014868:Water Deprivation / Q000502:physiology*
D003042:Cocaine