Sa. Mckee et al., A CONTEXT-SPECIFIC DETRIMENTAL EFFECT OF UCS PREEXPOSURE ON PLACE CONDITIONING WITH MORPHINE, Animal learning & behavior, 22(3), 1994, pp. 282-290
The effect of morphine preexposure on place conditioning with morphine
was investigated. In the first experiment, five injections of 10 mg/k
g morphine were administered to rats prior to place conditioning or ta
ste-aversion training with morphine. Although this number of preexposu
res retarded taste-aversion learning, there was no effect on place con
ditioning. In subsequent experiments we investigated the role of conte
xt blocking in UCS preexposure in place conditioning. In one experimen
t, preexposure to five morphine injections prior to place conditioning
resulted in a reduced place preference, compared with preexposure and
place conditioning in different contexts. However, the overall detrim
ental effect of morphine preexposure was questionable, because the rat
s that were preexposed were only marginally different from those that
were not preexposed. In a final experiment we examined the effect of a
context change from preexposure to place conditioning with 15 preexpo
sures and demonstrated a detrimental effect of preexposure on place co
nditioning that was context specific. These results support a role of
classical conditioning in place-preference conditioning with morphine.