CONDITIONED ANALGESIA IN THE SPINALIZED RAT. J.A. Salinas *, P.A. Illich, M.W. Meagher & J.W. Grau (SPON:R.A. King). Dept. of Psychology, Texas A&M Univ. College Station, TX 77843.

Pairing a neutral stimulus with an aversive event can endow the stimulus with the ability to elicit analgesia. It has been generally assumed that forebrain systems play a critical role in producing this conditioned analgesia. However, there is some evidence that classically conditioned responses can be established in spinalized subjects. The present tudy assesses whether conditioned changes in pain reactivit can be obtained in spinalized subjects. Six rats received a spinal transection at T2. Eight hrs after the surgery, subjects received differential conditioning (which controls for both pseudoconditioning and sensitization). One stimulus (CS+) was paired with intense tail shock (2-sec, 3-mA), while the other (CS-) was presented alone. Mild shock (10-sec, 1.0-mA) delivered to the left or right paw served as the CS+ and CS-. The subjects received 30 CS+ and 30 CS- trials spaced 1 min apart. Which stimulus served as the CS+ was counter-balanced across subjects. Pain reactivity was then tested one hour later with the tail-flick test. Subjects appeared analgesic during the CS+ relative to the CS-. This difference extinguished over the course of testing. A second experiment was then performed to determine whether the conditioned anlagesia is naltrexone reversible. We found that a large dose of naltrexone (14 mg/kg) did not attenuate the conditioned analgesia. Supported by NSF grant BNS 881981 to JWG.

Published in Society for Neuroscience Abstracts, 15, 1989.

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