Schedule induction conditions not only exaggerate intake but also enhance drug solution choice.
In previous research, rats exposed to daily, 3 h sessions of schedule-induced polydipsia (SIP) self-administered high doses of cocaine orally. However, a strong and durable preference for cocaine solution to water requires training in addition to mere oral self-administration exposure. If cocaine is dissolved in a preferred vehicle solution, and the vehicle is subsequently faded to water, then a strong preference for cocaine remains. A similar preference can be instituted for lidocaine solution. Such preferences may develop because the gustatory property of a drug becomes associated with the preferred vehicle and remains to function as a durable conditioned reinforcer after vehicle fading. To determine if drug preference is solely a function of this posited conditioning mechanism, or whether it also depends upon the SIP condition, rats were exposed to daily, 3 h sessions of single-ration feeding, rather than the SIP condition. A preferred vehicle (glucose/saccharin solution) was slowly faded from a 0.19 mg/ml lidocaine solution, which was presented concurrently with a choice for water. Although a preference for lidocaine solution to water could be generated, it occurred for only 5 out of 9 rats, and the preference was relatively unstable. By contrast, in two previous studies using SIP, 26 out of 27 rats maintained a preference for lidocaine solution. Thus, SIP not only exaggerates the amount of drug solution ingested but also contributes to the fixation of the associative drug solution choice.
Falk
J L
JL
Department of Psychology, Rutgers University, New Brunswick, NJ 08903, USA. jfalk@rci.rutgers.edu
Neal
S A
SA
Lau
C E
CE
D000818:Animals; D003213:Conditioning, Psychological / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004326:Drinking / Q000187:drug effects*; D005947:Glucose / Q000494:pharmacology; D008012:Lidocaine / Q000494:pharmacology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012054:Reinforcement, Psychology; D012439:Saccharin / Q000494:pharmacology; D012646:Self Administration
D008012:Lidocaine; D012439:Saccharin; D005947:Glucose