INVOLVEMENT OF DELTA-OPIOID RECEPTORS IN PHYSICAL-DEPENDENCE ON BUTORPHANOL

Butorphanol, a synthetic agonist/antagonist, has been shown to act on mu-, delta- and kappa-Opioid receptors. However, the relative involvem ent of opioid receptor subtypes in mediating butorphanol dependence is not known. In the present study, naltrindole, a delta-selective non-p eptide antagonist, was administered intracerebroventricularly (i.c.v.) to mask supraspinal delta-opioid receptors before and during the indu ction of butorphanol dependence. Treatment with naltrindole (0.1, 1, o r 10 nmol/5 mul per rat) significantly blocked naloxone-, a nonspecifi c antagonist, precipitated butorphanol withdrawal behaviors (escape be havior, teeth-chattering, wet shakes, forepaw tremors, ptosis, diarrhe a, body weight loss, and hypothermia) at all doses tested, and decreas ed ejaculation at 0.1 nmol in butorphanol-infused rats. In contrast, n altrindole treatment had no effect on yawning, nor urination. These re sults indicate that central delta-opioid receptors are involved in med iating butorphanol dependence in rats.