SELECTIVE INTERACTION OF DRUGS WITH A DISCRIMINABLE STIMULUS ASSOCIATED WITH NARCOTIC ACTION

Rats were trained to bar press on either 1 of 2 levers depending on whether they received an injection of morphine (10 mg/kg) or saline. The rats responded on the morphine-correct lever when injected with another narcotic, fentanyl, but responded on the saline-correct lever when injected with a narcotic antagonist or another CNS active, but non-narcotic, drug (e.g., amphetamine, apomorphine). The narcotic antagonist, naloxone, prevented the occurrence of the narcotic discriminable stimulus, but the rats responded on the morphine-correct lever when injected with morphine plus any of a number of potent CNS active, but non-narcotic compounds. These results were discussed with reference to the specificity of this procedure for detecting drugs with narcotic agonist or antagonist properties.