naltrindole and Substance-Related-Disorders

Topics: Animals; Aorta, Thoracic; Cocaine; Cyclic AMP; Electric Stimulation; Guinea Pigs; Humans; Ileum; In Vitro Techniques; Male; Mice; Muscle, Smooth; Opioid-Related Disorders; Rats; Receptors, Dopamine; Receptors, Opioid; Receptors, Serotonin; Substance-Related Disorders

This study investigated the effect of delta opioid receptor blockade by naltrindole on the development of physical dependence and tolerance to the antinociceptive and respiratory depressive effects of morphine in rats. Chronic morphine was delivered either by s.c. injection of increasing amounts of morphine over 5 days or by s.c. implantation of morphine pellets. Animals were cotreated with saline or naltrindole. Antinociception and respiratory depression were assessed after administration of a challenge dose of morphine, and withdrawal signs were determined after naloxone challenge. Naltrindole significantly attenuated the development of antinociceptive tolerance after all three chronic treatment regimens. In addition, rats pretreated with naltrindole displayed significantly fewer withdrawal symptoms and less weight loss after a naloxone challenge. In contrast, naltrindole did not prevent the development of tolerance to morphine-induced respiratory depression. These results imply that tolerance to antinociception and physical dependence involves adaptations at interacting mu and delta receptor populations, whereas tolerance to respiratory depression reflects actions of independent mu and delta receptor populations. These findings suggest that delta antagonists may have potential clinical application for decreasing the rapid development of tolerance to opiate-induced analgesia, while allowing for the development of protective tolerance to respiratory depression.

Topics: Animals; Drug Tolerance; Female; Male; Morphine; Naltrexone; Narcotic Antagonists; Rats; Rats, Sprague-Dawley; Substance-Related Disorders

The profile of actions of dihydroetorphine (DHE) concerning antinociception, tolerance and dependence was compared with those of morphine in mice. DHE at 1, 5, 10 or 20 micrograms/kg produced an antinociceptive effect in a dose dependent manner and 10 micrograms/kg was nearly equipotent to that of 10 mg/kg of morphine. The antinociceptive effect of both drugs was completely suppressed by 1 mg/kg of naloxone, while neither 10 mg/kg of naltrindole nor 1 mg/kg of nor-binaltorphimine had any suppressive effect. Mice tolerant to morphine antinociception were tolerant to DHE and vice versa. The naloxone-sensitive, locomotor accelerating activity was progressively enhanced by daily administration of DHE and morphine and a cross reverse tolerance developed between these compounds, suggesting that common mechanisms, especially mediating opioid receptors, underlay the activity enhancement. The development of physical dependence as evidenced by naloxone precipitated withdrawal signs, however, was not observed with daily treatment with DHE, 10, 20 and 100 micrograms/kg for 6 d. Thus, we demonstrated that DHE produces the antinociceptive effect mediated through mu opioid receptors without causing development of a physical dependence, suggesting that it is safe to use in the clinical therapy of patients suffering severe pain such as that accompanying cancer.

Topics: Analgesics; Animals; Body Weight; Drug Tolerance; Etorphine; Male; Mice; Mice, Inbred Strains; Morphine; Motor Activity; Naloxone; Naltrexone; Narcotic Antagonists; Pain Measurement; Substance-Related Disorders

Butorphanol, a synthetic agonist/antagonist, has been shown to act on mu-, delta- and kappa-opioid receptors. However, the relative involvement of opioid receptor subtypes in mediating butorphanol dependence is not known. In the present study, naltrindole, a delta-selective non-peptide antagonist, was administered intracerebroventricularly (i.c.v.) to mask supraspinal delta-opioid receptors before and during the induction of butorphanol dependence. Treatment with naltrindole (0.1, 1, or 10 nmol/5 microliters per rat) significantly blocked naloxone-, a nonspecific antagonist, precipitated butorphanol withdrawal behaviors (escape behavior, teeth-chattering, wet shakes, forepaw tremors, ptosis, diarrhea, body weight loss, and hypothermia) at all doses tested, and decreased ejaculation at 0.1 nmol in butorphanol-infused rats. In contrast, naltrindole treatment had no effect on yawning, nor urination. These results indicate that central delta-opioid receptors are involved in mediating butorphanol dependence in rats.

Topics: Animals; Butorphanol; Enkephalin, D-Penicillamine (2,5)-; Enkephalins; Male; Naltrexone; Rats; Rats, Sprague-Dawley; Receptors, Opioid, delta; Substance-Related Disorders

Recently, we demonstrated that delta opioid binding sites are involved in the development of morphine tolerance and dependence. In our present work, we studied the effect of the potent and selective delta antagonist, naltrindole (NTI), and its nonequilibrium analog, naltrindole 5'-isothiocyanate (5'-NTII), on the development of morphine tolerance and dependence in mice. In the acute model, mice injected with 100 mg/kg of morphine sulfate s.c. displayed acute tolerance 4 hr later as evidenced by a greater than 3-fold increase of the ED50 of morphine sulfate when compared to that of control mice. The acute tolerance was accompanied by the development of acute physical dependence as seen by the dramatic decrease in the amount of naloxone required to precipitate withdrawal jumping. Likewise, in the chronic model s.c. implantation of morphine pellets (75 mg free base) for 3 days produced tolerance and physical dependence. The ED50 of morphine sulfate in this case was increased by about 19-fold and the amount of naloxone needed to precipitate withdrawal jumping was 40 times lower than that required for acutely dependent mice. The development of acute tolerance and dependence was suppressed markedly in mice pretreated with NTI before induction of tolerance and dependence with 100 mg/kg of morphine sulfate. Multiple administration of either NTI or 5'-NTII before and during implantation with morphine base pellets also inhibited substantially the development of morphine tolerance and dependence.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Drug Implants; Drug Tolerance; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalins; Indoles; Isothiocyanates; Male; Mice; Morphinans; Morphine; Naltrexone; Narcotic Antagonists; Nociceptors; Receptors, Opioid; Receptors, Opioid, delta; Substance-Related Disorders; Thiocyanates

Chronic treatment with naloxone (Nx) or naltrexone (Ntx) induces paradoxical analgesia. In the present study, the effects of chronic treatment with opioid receptor antagonists, such as nor-binaltorphimine (nor-BNI) for kappa and naltrindole (NTI) for delta receptors, on analgesic response using the hot plate test and on morphine physical dependence in rats were examined. The hot plate latency was significantly increased by pretreatment with Nx (5 mg/kg, s.c.), nor-BNI (20 mg/kg, i.p.) or NTI (20 mg/kg, i.p.) for 5 days. After chronic pretreatment with these antagonists, the rats were treated with morphine-admixed food (0.5 mg/g of food) for 3 days. Chronic pretreatment with Nx and NTI significantly increased Nx precipitated body weight loss in morphine dependent rats, while chronic pretreatment with nor-BNI produced small increase. These results indicate that chronic treatment with nor-BNI or NTI as well as with Nx induces obviously paradoxical analgesia, and that chronic blockade of mu or delta may enhance the development of physical dependence on morphine.

Topics: Animals; Body Weight; Indoles; Male; Morphinans; Morphine; Naloxone; Naltrexone; Narcotic Antagonists; Pain Measurement; Rats; Rats, Inbred Strains; Substance Withdrawal Syndrome; Substance-Related Disorders