Table 1.
Conditioning | Test | ||||
---|---|---|---|---|---|
CS Type | Drug | Trials | |||
Light | X | Saline | X | 8 | Light? |
Compound | Naltrexone | ||||
No CS |
Note. Animals were conditioned to fear a light CS, compound light-noise CS or trained in the absence of an explicit CS (No CS group). Eight-trial conditioning proceeded under the influence of the opioid antagonist naltrexone or the saline vehicle. The CS type and drug condition were manipulated using a 3 × 2 factorial design. The following day, animals were tested to one presentation of the light CS.