Prior work suggests that spinal neurons can support a simple form of instrumental learning.
Rats in the contingent, but not in the noncontingent, group learn to maintain a flexion response. In a subsequent test phase, all subjects receive contingent shock. We have shown that naltrexone, an opioid antagonist, injected i.p. blocks the induction of the learning deficit. In Experiment 1, we administered various doses of naltrexone intrathecally to verify that it was having its action on spinal neurons, and at the same time, extablished the effective intrathecal dose. In Experiment 2, we determined whether the opioid antagonist had its effect during training or testing.