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 11,717 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The development process of physical dependence on and tolerance to morphine has been explored in rats treated with morphine-admixed food (0.5 mg/g of food) during 1 to 7 days. 2. In the morphine-treated animals, body weight loss was observed after the abrupt morphine withdrawal. 3. Intensity and time course of the weight loss were correlated to the morphine treatment. 4. On the other hand, the morphine-treated rats showed abnormal behaviors, such as diarrhea, ptosis, teeth chattering, salivation, body shakes, vocalization, nose bleed, irritability, aggression, lacrimation and writhing upon naloxone injection. 5. Loss of body weight, measured 3 hours after naloxone injection, was also correlated to the duration of morphine treatment. 6. Tolerance to the analgesic effect of morphine developed within one day in rats treated with morphine-admixed food. 7. The drug-admixed food ingestion method has the advantage of rapidly inducing a high degree of physical dependence and tolerance without causing morbidity or lethality in animals. It also eliminates the need for excessive handling of animals.
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PMID:Development of physical dependence on and tolerance to morphine in rats treated with morphine-admixed food. 668 88

We examined the locomotor-enhancing action of mu-opioid receptor agonists, such as morphine and [D-Ala2, N-MePhe4, Gly-ol5]enkephalin (DAMGO), and physical dependence on morphine in diabetic and nondiabetic mice. Morphine (5-20 mg/kg, s.c.) and DAMGO (1-4 nmol, i.c.v.) had a dose-dependent locomotor-enhancing effect in both nondiabetic and diabetic mice. The locomotor-enhancing effects of morphine and DAMGO were significantly less in diabetic mice than in nondiabetic mice, and were significantly reduced after pretreatment with either beta-funaltrexamine (20 mg/kg, s.c.), a selective mu-opioid receptor antagonist, or naloxonazine (35 mg/kg, s.c.), a selective mu1-opioid receptor antagonist. Both diabetic and nondiabetic mice were chronically treated with morphine (8-45 mg/kg, s.c.) for 5 days. During this treatment, neither diabetic nor nondiabetic mice showed any signs of toxicity. After morphine treatment, withdrawal was precipitated by injection of naloxone (0.3-10 mg/kg, s.c.). Several withdrawal signs, such as weight loss, diarrhea, ptosis, jumping and body shakes, were observed after naloxone challenge in morphine-dependent nondiabetic mice. Although morphine-dependent diabetic mice showed greater weight loss than nondiabetic mice, the incidence of jumping and body shakes after naloxone challenge in diabetic mice were lower than that in nondiabetic mice. These results suggest that diabetic mice are selectively hyporesponsive to mu1-opioid receptor-mediated locomotor enhancement. Furthermore, diabetes may affect mu1-opioid receptor-mediated naloxone-precipitated signs of withdrawal from physical dependence on morphine.
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PMID:Modification of mu-opioid agonist-induced locomotor activity and development of morphine dependence by diabetes. 763 31

The ontogeny of tolerance to mu opiate antinociception and the behavioral and endocrine profiles of the opiate withdrawal syndrome were studied in rats. Animals were treated with saline or an increasing dose regimen of morphine for 5 days (5-25 mg/kg b.i.d. s.c.) and were tested 36 hr later for morphine or sufentanil antinociception in the hot-plate paw-lift test, or withdrawal was precipitated with 5 mg/kg of naloxone 12 hr after the last chronic morphine dose. Twenty-seven-, 20- and 15-day-old rats all developed tolerance as indicated by a rightward shift of the dose-response curve after chronic morphine. Animals treated on days 4 to 8 and tested on day 10 did not develop tolerance to the same chronic dose regimen used in older animals. In contrast to the observed developmental difference in tolerance, both neonatal and weanling rats developed physical dependence after morphine treatment, as evidenced by the presence of withdrawal symptoms after naloxone administration. Withdrawal in weanling rats was characterized by ptosis, piloerection, abnormal posture, forepaw treading, vocalization on touch and mastication. In addition, both serum corticosterone and adrenocorticotropic hormone secretion were increased during passive withdrawal. The behaviors constituting the withdrawal syndrome precipitated in neonates were distinct from those in weanling rats. Spontaneous vocalization, wall climbing, tremor, mouthing and increased locomotion were all observed. As in the older animals, both serum corticosterone and adrenocorticotropic hormone secretion were elevated during passive withdrawal. Tremor also was induced in opiate naive neonates when naloxone (5 mg/kg) was administered 2 hr after a single 25-mg/kg morphine injection. Brain and serum morphine levels and the time course of antinociception were not altered by chronic morphine treatment at any age. Saturation binding assays in brain homogenates indicated that chronic morphine did not produce changes in receptor number or affinity for the antagonist. The shift induced by the guanine nucleotide Gpp(NH)p (10 microM) from high to low affinity on days 27 and 10, respectively, was not altered by chronic morphine treatment. These data indicate that 10-day-old rats are refractory to developing tolerance relative to older animals, and that changes in receptor number or coupling to guanine nucleotide proteins do not accompany tolerance to this regimen.
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PMID:The ontogeny of mu opiate tolerance and dependence in the rat: antinociceptive and biochemical studies. 779 Nov 9

The destruction of N-methyl-D-aspartate (NMDA) receptor-bearing neurons by insulin-induced hypoglycemia has long been known to be due to excessively released aspartate and glutamate. In this study, the effects of NMDA-bearing neuron destruction by insulin-induced hypoglycemia on the development of morphine (M) physical dependence, which was found related to functional states of NMDA receptors, were investigated. NMDA receptor antagonists CGP 39551 and MK-801 were used to see whether they could change intensity of precipitated abstinence syndrome by preventing destruction. Therefore, two groups of fasting rats injected IP with physiological saline, and another two groups given IP 10 mg/kg CGP 39551 and 0.5 mg/kg MK-801 received 15 IU/kg crystalline zinc insulin IP. After 2 h, the rats were orally given 2 x 4 ml of 5% glucose solution. On the third day, two pellets containing 75 mg base M were SC implanted to all rats. On the sixth day, they were IP given 2 mg/kg naloxone (NL). Then jumps, wet-dog shakes, and defecation were counted while diarrhea and ptosis were rated for 15 min. The rats given insulin manifested significantly more intense NL-precipitated abstinence syndrome than controls. The rats administered CGP 39551 showed a less intense physical dependence than those injected with only insulin. But, the intensity was still significantly higher than controls. In the rats that received MK-801, the abstinence syndrome was more or less equal to that in controls.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Morphine physical dependence intensification by hypoglycemia: NMDA receptor involvement. 793 7

Pregnant rats were SC injected with physiological saline (control) or 10 mg/kg morphine (morphine group) or 2 mg/kg naloxone (naloxone group) three times daily during the last 5 days of gestation. Three weeks after birth, male young rats of each group were taken and placed in separate cages. When their body weight reached 130-150 g, 10 rats from control, morphine, and naloxone groups were SC implanted with two pellets containing 75 mg morphine base (total 150 mg). Three days following implantation, rats were IP given 2 mg/kg naloxone for precipitated abstinence syndrome. Immediately after naloxone injection, rats were strictly observed for 15 min and jumping, wet-dog shakes, teeth-chattering, diarrhoea, defecation, and ptosis counted or rated. All abstinence syndrome signs were significantly higher in the morphine or naloxone group than in control. On the basis of the previous experimental findings supporting the idea that opiate physical dependence is related to the binding of opiate, possibly other than their own, to NMDA receptors and the upregulation and/or supersensitivity associated with the binding, the intensification of morphine dependence has been attributed to the long-lasting NMDA receptor upregulation and/or supersensitivity.
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PMID:Prenatal exposure to morphine or naloxone intensifies morphine dependence at maturity. 846 3

A cannabinoid antagonist, SR 141716A, dose dependently precipitated a behavioral withdrawal syndrome in rats continuously infused i.p. for only 4 days with relatively low-dose regimens of delta 9-tetrahydrocannabinol. The following dose regimens, expressed as mg/kg/24 hr, were used for days 1 through 4: high-12.5, 25, 50 and 100; medium-2.5, 5, 10 and 20; and low-0.5, 1, 2 and 4. The major withdrawal signs of the syndrome were scratching, rubbing face with paws, licking, wetdog shakes, arched back and ptosis (at least 50% closure of eyelids). At the highest dose regimen, other signs noted in fewer subjects were biting, tongue rolling, retropulsion, head shakes, extended limbs or high stepping, ataxia, myoclonic spasms and front paw treading. During abrupt withdrawal (delta 9 tetrahydrocannabinol was discontinued and vehicle substituted) abstinence signs were also noted; however, except during a 48-hr observation period, withdrawal was not sufficiently robust to achieve statistical significance. The results of this study provide evidence that a modest course of delta 9-tetrahydrocannabinol can produce physical dependence. Hence, the risk and incidence of marijuana dependence in humans may be greater than previously projected.
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PMID:Dependence on delta 9-tetrahydrocannabinol: studies on precipitated and abrupt withdrawal. 881 14

The ability of a pretreatment with the cholecystokininB-receptor (CCK[B]) antagonist L-365,260 to prevent the development of morphine dependence was studied in normal and neuropathic (unilateral peripheral neuropathy) rats. A 4-day pretreatment regimen with two daily s.c. injections of either saline+saline, saline+morphine (3.0 mg/kg) or L-365,260 (0.2 mg/kg)+morphine was used, and withdrawal was precipitated by an injection of naloxone (1.0 or 2.0 mg/kg i.v.) at 24 h after the last pretreatment injection. After pretreatment with morphine alone, physical dependence developed in both normal and neuropathic rats. However, the incidence of teeth chattering and ptosis was higher in neuropathic rats. Pretreatment with the combination of L-365,260 and morphine prevented the expression of teeth chattering, ptosis, diarrhea, writhing and piloerection, but was devoid of effects on the exploratory activity among both groups of rats. These results suggest that endogenous CCK acting on CCK(B)-receptors may be involved in the development of morphine dependence both in normal and neuropathic rats.
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PMID:The selective cholecystokininB receptor antagonist L-365,260 diminishes the expression of naloxone-induced morphine withdrawal symptoms in normal and neuropathic rats. 949 17

Using N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2, 4-dichloro-phenyl)-4-methyl-1H-pyrazole-3-carboxamide. HCl (SR 141716A), a cannabinoid antagonist, several investigators (deFonseca et al., 1997; Aceto et al., 1995, 1996; Tsou et al., 1995) demonstrated physical dependence on THC [Delta9-tetrahydrocannabinol]. This demonstration prompted us to determine whether anandamide, an endogenous cannabinoid agonist, would also produce physical dependence. A low-dose regimen (10, 20, 40 and 40) or a high-dose regimen (25, 50, 100 and 100) expressed as mg/kg/24 hr was infused i.p. on a continuous basis, from days 1 through 4, respectively. During the infusion, especially at the high-dose regimen, the rats became immobile and developed eyelid ptosis. Abrupt discontinuation of anandamide did not elicit rebound behavioral activity. Neither arachidonic acid, a precursor and metabolite of anandamide (50, 100, 200 and 200 mg/kg/24 hr on days 1 through 4, respectively), nor 2-Me-F-AN [2-methylarachidonyl-(2'-fluoroethyl)-amide], a metabolically stable analog of anandamide (5, 10, 20 and 20 mg/kg/24 hr for 4 days, respectively), had remarkable effects. Notably, groups pretreated with anandamide or 2-Me-F-AN and challenged with SR 141716A did not show significantly elevated behavioral scores when compared with SR 141716A controls. On the other hand, nearly all groups receiving SR 141716A showed significant activation of these behaviors compared with vehicle controls, which suggests that this cannabinoid antagonist itself was activating behavior. We concluded that anandamide has little if any capacity for physical dependence. The finding that SR 141716A activated behavior supports the hypothesis that the cannabimimetic system exerts a depressant effect in the CNS.
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PMID:Anandamide, an endogenous cannabinoid, has a very low physical dependence potential. 980 86

The present study examined the effect of the gamma-aminobutyric acidB (GABA(B)) receptor agonist, baclofen on naloxone-induced withdrawal signs in morphine-dependent rats and modification by the antagonist, 3-aminopropyl-cyclohexylmethylphosphinic acid (CGP 46381). Morphine was administered via mini-osmotic pumps for 7 days to induce physical dependence. Baclofen (20 mg kg(-1)) decreased stereotyped head movements, chewing, chatter, ptosis and body weight loss, induced by naloxone (10 mg kg(-1)) in morphine-dependent rats. CGP 46381 (20 mg kg(-1)) reversed the effects exerted by baclofen on stereotyped head movements, ptosis, and weight loss and partially reversed the effect of baclofen on chewing. It can be concluded that baclofen has some potential in the treatment of opioid withdrawal and that GABA(B) receptors may be implicated in such a withdrawal.
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PMID:Attenuation of morphine withdrawal signs by the GABA(B) receptor agonist baclofen. 1179 9

To explore the effect of sinomenine on the nitric oxide (NO)/neural nitric oxide synthase (nNOS) system in the cerebellum and spinal cord of morphine-dependent and morphine-withdrawal Kunming mice, mice were subjected to injection of morphine with an increasing dose for 5 d, and then were treated with sinomenine (40 mg/kg, i.p.) for another 5 d. Naloxone was used to develop acute withdrawal, and the withdrawal syndromes, including teeth chattering, twisting, straightening, sneezing and ptosis, were investigated. nNOS mRNA expressions in the cerebellum and spinal cord were determined by semi-quantitative RT-PCR. nNOS activity and NO level were determined by the chemistry-colorimetry and nitrate reductase-reduction, respectively. The results obtained were as follows: (1) Sinomenine restored the decrease in body weight and alleviated the signs of morphine-withdrawal in mice. (2) Sinomenine also reduced the increases in nNOS mRNA expression and nNOS activity resulting from morphine-dependence, and simultaneously attenuated the high level of NO in both tissues following morphine-withdrawal. (3) Administration of sinomenine alone did not develop physical dependence in mice. The results obtained indicate that sinomenine may attenuate morphine addiction and significantly alleviate morphine-withdrawal symptoms, and the mechanism may be associated with the effect of sinomenine on the NO/nNOS system in the cerebellum and spinal cord.
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PMID:[Effects of sinomenine on NO/nNOS system in cerebellum and spinal cord of morphine-dependent and withdrawal mice]. 1757 82


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