Response suppression during cumulative dosing: a role for Pavlovian conditioning.
Key pecking by pigeons was maintained by a fixed-ratio 15 or a fixed-interval 15 s schedule of food presentation. Sessions consisted of six blocks that included a 4 min blackout then 2 min of schedule time or six food presentations. Cumulative dose-response curves were assessed by injecting saline at the start of the second block and increasing cocaine doses at the onset of subsequent blocks. Repeated cumulative dosing often shifted dose-response curves to the left, and these effects appeared to be due to the reliable correlation between smaller and larger doses administered early and later in the session. When saline was substituted for the larger doses later in the session, dose-response curves initially remained shifted to the left, and continued substitution eventually resulted in curves shifting to the right. Cumulative dosing was compared with two noncumulative dosing procedures: (a) pre-session dosing and (b) one cocaine injection at the block in which the same cumulative dose would be tested, with saline injections at the other blocks (except the first). Noncumulative dosing tended to produce more reliable (repeatable) results than did cumulative dosing, and at least one interpretation is the possibility of conditioning factors that may be present in cumulative-dosing but not in noncumulative-dosing procedures.
Walker
D J
DJ
Department of Psychology, University of Florida, Gainesville, USA. dwalker@dacc.uchicago.edu
Branch
M N
MN
D000818:Animals; D003042:Cocaine / Q000494:pharmacology*; D010856:Columbidae; D003214:Conditioning, Classical / Q000502:physiology*; D003216:Conditioning, Operant / Q000187:drug effects*; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005502:Food; D008297:Male; D012055:Reinforcement Schedule; D012054:Reinforcement, Psychology
D018765:Dopamine Uptake Inhibitors; D003042:Cocaine