Tyr-W-MIF-1-induced conditioned place preference

Based on the evidence that Tyr-Pro-Trp-Gly NH, (Tyr-W-MIF-1) produced dose- dependent, mu-opiate agonistic/antagonistic effects, we investigated whethe r Tyr-W-MIF-1 exhibited similar properties in the conditioned place prefere nce (CPP) test. To examine the opiate agonistic effects on CPP, rats were c onditioned with alternating ICV injections of saline and Tyr-W-MIF-1 (0 or 200 mu g). This procedure resulted in Tyr-W-MIF-1-induced CPP. To examine t he opiate antagonistic properties of low doses of Tyr-W-MIF-1, morphine-ind uced CPP was challenged with Tyr-W-MIF-1 (0, 25, 50, or 100 mu g). Morphine -induced CPP was not affected by Tyr-W-MIF-1 at these doses. These findings show that in the CPP test Tyr-W-MIF-1 produced opiate agonistic effects at the high dose and was without opiate antagonistic properties at lower dose s. (C) 1999 Elsevier Science Inc. All rights reserved.