Some relations between tolerance and physical dependence to morphine in mice

Tolerance to morphine analgesia and precipatated physical dependence were studied in mice under different conditions. There was a gradual loss of tolerance during the continous absorption of morphine from a pellet. Tolerance was decreased by nalorphine during morphine absorption. An attenuated physical dependence was observed two or four days after a single dose of morphine. In animals previously treated with pellets of morphine, single doses of morphine induced less tolerance than in mice that had never been implanted with pellets; in both cases cycloheximide prevented development of tolerance. Tolerance persisted for more than 20 days after absorption of the morphine pellet. These results reinforce the hypothesis that tolerance and physical dependence are produced by a similar mechanism and that an inhibitory process of tolerance exists.     

Development of narcotic tolerance and physical dependence: effects of Pro-Leu-Gly-NH2 and cyclo (Leu-Gly)

Administration of Pro-Leu-Gly-NH2 (MIF) and cyclo (Leu-Gly) blocked the development of tolerance to and physical dependence on morphine, induced by the pellet implanation procedure in mice. Inhibition of tolerance development by peptides was evidenced by the presence of an analgesic response (increase in jump threshold) as determined by measuring the jump threshold to an increasing electric current, after a challenge dose of morphine (40 mg/kg). The same dose of morphine did not alter the jump threshold in morphine tolerant mice which were injected with saline prior to pellet implantation. The inhibition of the development of physical dependence on morphine by these peptides was evidenced by the antagonism of the hypothermic response which occurs during abrupt or naloxone-induced withdrawal. The naloxone-induced withdrawal jumping response was unaffected by these peptides. Dose-response experiments indicated that cyclo (leu-Gly) was much more potent than MIF in these tests. These peptides, when given after the development of tolerance and dependence, did not modify either the analgesic response to morphine or the symptoms of abrupt and naloxone-precipitated withdrawal. The inhibition of development of analgesic tolerance and physical dependence was not associated with changes in brain morphine concentration. The data indicate that these peptides do not interfere withe the morphine-morphine receptor complex formation but alter a subsequent step in the genesis of some aspects of tolerance and dependence processes.     

Influence of 5,6-dihydroxytryptamine on morphine tolerance and physical dependence

The intracerebral administration of 5,6-dihydroxytryptamine (5,6-DHT) in the mouse inhibited the development of tolerance to and physical dependence on morphine induced by morphine pellet implantation. Reduction in tolerance development by 5,6-DHT was evidenced by the decreased amount of morphine necessary to produce analgesia and reduction in dependence development by the increase in the amount of naloxone necessary to induce precipitated withdrawal jumping in comparison with morphine-implanted animals receiving saline. Further evidence that 5,6-DHT reduced dependence development on morphine was evidenced by the fact that 5,6-DHT decreased the loss in body weight which occurred after abrupt morphine withdrawal. At the dose of 5,6-DHT used in this study (60 μg of the creatinine sulfate dihydrate 24 hr prior to morphine pellet implantation), the 5-HT level in the brain 4 days later was 75% of that of the control group while catecholamine levels remain unchanged. These studies substantiate the suggestion from this laboratory that central serotonergic system may be associated in the development of morphine tolerance and dependence.     

PRELIMINARY STUDIES ON INCREASED NALOXONE POTENCY AND ITS RELATIONSHIP TO MORPHINE TOLERANCE AND DEPENDENCE IN MICE

1. Morphine pretreatment (8 0 mg/kg s.c.) induced no overt tolerance to its antinociceptive effect in mice 4 h later, but enhanced the antagonistic potency of naloxone. 2. A molecular sieve morphine pellet implanted for 24 h induced measurable tolerance, but the relative potency of naloxone was not significantly different from that observed after single-dose morphine pretreatment. The development of tolerance and increased naloxone potency do not, therefore, run parallel. 3. Naloxone-precipitated withdrawal symptoms were observed after single-dose morphine and after pellet implantation. However, molecular sieve morphine pellet implantation induced a higher degree of dependence as compared with single dose morphine pretreatment. 4. These results indicate that the rate of development of increased naloxone potency and of morphine tolerance and dependence do not run parallel. This implies that caution must be exercised in regarding increased naloxone potency as a sensitive indicator of the initiation and development of tolerance and dependence to morphine.     

Effects of naltrexone pellet implantation on morphine tolerance and physical dependence in the rat

• 1.1. The effect of naltrexone pellets containing either 10 or 30 mg of naltrexone base on the development of tolerance and physical dependence on morphine was assessed in male Sprague-Dawley rats. Tolerance-dependence on morphine was induced by s.c. implantation of six morphine pellets, each containing 75 mg morphine base for 7 days.
• 2.2. Naltrexone pellet implantation blocked the development of tolerance to the analgesic and hyperthermic effects of morphine. Similarly, naltrexone pellet implantation reversed morphine withdrawal-induced body weight loss. The effect of pellets containing 10 and 30 mg naltrexone did not differ.
• 3.3. The effect of naltrexone (10 mg) pellet implantation on various signs of naltrexone-precipitated withdrawal such as body weight loss, hypothermia and increases in urinary and fecal output was investigated. Naltrexone pellet implantation did not alter the naltrexone-precipitated withdrawal-induced body weight loss. Concurrent naltrexone pellet implantation blocked the naltrexone-precipitated withdrawal-induced hypothermia, increased fecal and urinary output in morphine-dependent rats.
• 4.4. These results indicate that a single pellet of 10 mg of naltrexone can effectively block morphine tolerance and physical dependence in the rat. Such a procedure may be useful in studying biochemical, endocrinological and immunological mechanisms involved in opioid addiction processes.

     

Pharmacodynamics and kinetics of loss of tolerance and physical dependence on morphine induced by pellet implantation in the rat.

The decay characteristics of tolerance and physical dependence on morphine induced by a pellet implantation procedure were determined in male Sprague-Dawley rats. Rats were implanted subcutaneously with 6 morphine pellets during a 7-day period. The pellets were removed, and at various times thereafter tolerance to the analgesic and hyperthermic effects of morphine was measured by determining the response in rats implanted with morphine and placebo pellets. Similarly, the physical dependence was assessed by monitoring withdrawal signs following an injection of naloxone. A high degree of tolerance developed to the analgesic and hyperthermic effects of morphine. Similarly, a high degree of physical dependence also developed as evidenced by a high incidence of jumping response, teeth chattering and production of fecal boli induced by injections of naloxone. In addition, loss of body weight and body temperature also occurred. The analgesic and hyperthermic response to morphine recovered very gradually. There was no significant difference in the analgesic and hyperthermic responses to morphine on day 4 after the pellet removal in rats implanted with morphine and placebo pellets. The decay of tolerance was linear with time for the analgesic effect (r = 0.98) and for the hyperthermic effect (r = 0.93). The change in symptoms of physical dependence on morphine with time depended on the specific symptom monitored. The average number of jumps and teeth chattering decreased with time in a linear fashion with r values of 0.98 and 0.99, respectively. However, the number of fecal boli and wet dog shakes increased linearly with time (r = 0.97). The recovery of loss of body weight was also linear with time. Thus, it is clear that fecal boli and wet dog shakes, which increase in number as the dependence decays, are signs of a low degree of dependence. The results suggest that different central or peripheral mechanisms may be operating in different withdrawal symptoms. These studies may prove to be useful when studying the mechanisms involved in the induction and reversibility of tolerance and dependence processes, and in long-term effects of opiates at a time when the tolerance and physical dependence is no longer evident.     

The synthesis rate and turnover time of 5-hydroxy-tryptamine in brains of rats treated chronically with morphine.

1. Four schedules of subcutaneous pellet implantation were used to induce tolerance to and physical dependence on morphine in Sprague-Dawley rats. 2. The schedules included implantation of four morphine pellets (each containing 75 mg of morphine free base) during a 3 day period (schedule 1); six pellets during 3 days (schedule 2); six pellets during 7 days (schedule 3) and ten pellets during a 10 day period (schedule 4). 3. A high degree of tolerance and dependence on morphine, comparable to that induced in mouse by implantation of a single morphine pellet for 3 days, was produced with schedule 4. 4. Brain 5-hydroxytryptamine (5-HT) turnover rates as measured by rate of accumulation of 5-HT after monoamine oxidase inhibition by pargyline were not different in rats rendered tolerant to and dependent on morphine according to schedules 1 to 4 when compared with corresponding placebo pellet-implanted rats. 5. The turnover rates of 5-HT in brain of morphine-and placebo pellet-implanted rats (schedule 4) from which the pellets had been removed for 24 h were also similar. 6. It is concluded that tolerance to, and physical dependence upon morphine in the rat is not associated with changes in brain 5-HT dynamics.     

Effect ofPanax ginseng on the development of morphine induced tolerance and dependence (VI). On the oral administration of ginseng ether fraction and saponins

The present study was undertaken to determine the inhibitory effects of orally adminstered ginseng saponins(GS), protopanaxadiol saponins(PD), protopanaxatriol saponins(PT) and ginseng ether fraction(GE) on the development of morphine induced tolerance and physical dependence in mice and also to determine the hepatic glutathione contents. GS, PD and PT inhibited significantly the development of morphine induced tolerance and physical dependence, but GE was effective only on the inhibition of the development of morphine induced physical dependence. GS, PD, PT and GE also inhibited the hepatic glutathione level decrease induced by morphine multiple injections.     

Attenuation of tolerance to,and physical dependence on,morphine in the rat by inhibition of nitric oxide synthase

• 1.1. The effect of N^G-monomethyl-l-arginine (NMMA), an inhibitor of nitric oxide synthase (NOS), on the development of tolerance to and physical dependence on morphine was determined in the rat.
• 2.2. Male Sprague-Dawley rats were rendered tolerant to and dependent on morphine by the subcutaneous implantation of four morphine pellets (each containing 75 mg morphine base) during a 3 day period. Placebo pellet implanted rats served as controls.
• 3.3. Chronic administration of morphine resulted in the development of tolerance to the analgesic action of morphine. Twice daily injections of NMMA (4 or 8 mg/kg) attenuated the tolerance to morphine as evidenced by higher analgesic response in NMMA treated than in vehicle treated morphine tolerant rats.
• 4.4. Chronic administration of morphine also resulted in the development of physical dependence as evidenced by the appearance of a variety of symptoms including stereotyped jumping response following naltrexone injection. Concurrent treatment with NMMA inhibited naltrexone-induced jumping response but other responses like fecal boli formation, wet dog shakes, teeth chattering, rearing and ejaculations were not modified.
• 5.5. It is concluded that inhibition of NOS can attenuate the development of tolerance to, and physical dependence on, morphine in the rat. However, it appears that higher doses of NOS inhibitors are required in the rat than in the mouse for blockade of both tolerance and physical dependence processes.

     

Tolerance-dependence and serum elimination of morphine in rats implanted with morphine pellets.

1. In order to determine whether the degree of tolerance to and physical dependence on morphine induced by pellet implantation procedure in the rat depends on the dose used and the kinetic parameters, the effect of implantation of different number of pellets on tolerance-dependence and elimination kinetics of morphine from serum was determined. 2. Male Sprague-Dawley rats were implanted subcutaneously with pellets. Each pellet contained 75 mg of morphine free base. Three schedules of implantation were used. They included 2 pellets during a 3-day period (2/3), 4 pellets during a 3-day period (4/3) and 6 pellets during a 7-day period (6/7). Placebo pellets which did not contain morphine were implanted in rats which served as controls. 3. The degree of tolerance to and physical dependence on morphine increased as the number of morphine pellets implanted increased. 4. In separate groups of rats implanted with pellets, elimination kinetics of morphine was studied using radioimmunoassay. The kinetic parameters were: area under serum morphine concentration time curve (AUC0----infinity), serum concentration of morphine extrapolated to time zero (Cmax), half-life (t1/2), elimination rate constant (k), mean residence time (MRT) and total body clearance (Clt). 5. The AUC0----infinity and Cmax increased in proportion to the number of pellets implanted. The t1/2, k, MRT and Clt values for 2/3 and 4/3 schedules did not differ, but for 6/7 schedule were significantly different from the other two schedules. The degree of tolerance to and physical dependence on morphine was directly related to the AUC0----infinity and Cmax. The longer t1/2 and MRT and lower Clt and k values in 6/7 schedule may reflect a saturation of glucuronic acid transferase, the main enzyme metabolizing morphine in the liver, and may account for the greater degree of tolerance and physical dependence.     

Tolerance and dependence induced by morphine-like pituitary peptides in rats

Summary An extract from porcine pituitaries containing peptides with opiate-like activity (endorphins) was investigated for possible tolerance/dependence liability in rats. Repeated intraventricular administration of endorphins induced a degree of tolerance similar to that induced by normorphine. Rats made tolerant to morphine by repeated pellet implantation proved cross-tolerant to the pituitary extract as well as to synthetic methionine-enkephalin. Naloxone given to rats, repeatedly pretreated with endorphins, precipitated a withdrawal syndrome strongly resembling that induced in rats treated with normorphine. Withdrawal precipitated in morphine-dependent rats was suppressed by intraventricularly applied endorphins. The results suggest that identical sites and mechanisms are involved in the development of tolerance/dependence induced by opiates and pituitary endorphins.     

Morphine analgesia, tolerance and physical dependence in the adrenalectomized rat

1. Adrenalectomy reduced the median antinociceptive dose (AD50) of morphine in male Sprague-Dawley rats. The antinociceptive effect was assessed by the tail-flick method of D'Amour & Smith (1941).2. Tolerance to the antinociceptive effect of morphine developed in adrenalectomized and sham-operated rats after chronic exposure to morphine. Development of tolerance did not significantly alter the increased sensitivity of adrenalectomized rats to the antinociceptive effect of morphine.3. Adrenal weights were not increased in rats rendered physically dependent on morphine by subcutaneous implantation of a morphine pellet. Withdrawal, induced by intraperitoneal injection of naloxone hydrochloride, 4 mg/kg, or by removal of the implanted pellet, resulted in a rapid increase in adrenal weight.4. In morphine-dependent animals, the incidence of abstinence signs and body weight loss during precipitated withdrawal did not appear to be significantly influenced by adrenalectomy or by corticosterone-pretreatment.     

Antinarcotic effects of the standardized ginseng extract G115 on morphine

The study was undertaken to determine the antagonism of morphine analgesia by the standardized ginseng extract G115 from Panax ginseng, the inhibitory effects of orally administered G115 on the development of morphine-induced tolerance and physical dependence, the hepatic glutathione levels, the inhibitory effects of intraperitoneally administered G115 on the dopamine receptor supersensitivity, and the reverse tolerance to the locomotor accelerating effect of morphine. G115 significantly inhibits the development of morphine-induced tolerance and physical dependence, the hepatic glutathione level decrease induced by morphine multiple injections, the development of morphine-induced dopamine receptor supersensitivity, and reverse tolerance to the locomotor accelerating effect of morphine. It did not, however, antagonize morphine analgesia.     

Antagonizing effect of aspartic acid on the development of physical dependence on and tolerance to morphine in the rat

As free amino acids in the brain have a role in the development of physical dependence on and tolerance to morphine, and in the mechanism of action of some drugs, the effects of aspartic acid which antagonizes some effects of the single dose of morphine were studied during the development of the physical dependence on morphine and after the withdrawal of morphine. 108 rats were given morphine and aspartic acid in different combinations in drinking water for 30 days. Every tenth day the dose of morphine was increased: At the end of this period some of them in each group continued or began to receive aspartic acid depending on the experimental conditions after the withdrawal of morphine. During the experiments body weight, spontaneous motor activity and analgesic threshold were determined. Aspartic acid prevented the alterations induced by morphine during the development of physical dependence and tolerance. Furthermore the rats that received aspartic acid after the withdrawal showed no body weight loss.     

Increase in plasma cyclic AMP levels elicited by naloxone in morphine-dependent male mice

Naloxone increased the levels of plasma cyclic AMP in morphine-dependent male mice in which a morphine pellet had been implanted for 72 hr, but not in the nondependent mice. The effect of naloxone on the cyclic AMP levels disappeared 24 hr after the removal of the morphine pellet. Pretreatment with propranolol, hexamethonium or adrenalectomy, but not with atropine or phentolamine inhibited the effect of naloxone. These results suggest that naloxone increases the level of plasma cyclic AMP by releasing catecholamines from the adrenal medulla, thereby activating the adenylate cyclase in the tissues through the stimulation of β-adrenergic receptors. A moderate increase in plasma cyclic AMP was also seen in morphine-dependent mice 1 hr after the removal of the morphine pellet. It is proposed that the increase in the levels of plasma cyclic AMP elicited by naloxone-precipitated or abrupt withdrawal is one of the withdrawal symptoms and probably can be used as a screening method for assessing the degree of physical dependence in laboratory animals.     

Effects of cholane compounds on the development of morphine tolerance

The present study was undertaken to determine the inhibitory effects of cholane compounds, ursodeoxycholic acid (UDCA) and chenodeoxycholic acid (CDCA) on the development of morphine-induced tolerance and physical dependence, and also to determine the hepatic glutathione contents. UDCA and CDCA inhibited the development of morphine-induced tolerance and physical dependence significantly. UDCA inhibited the hepatic glutathione decrease induced by morphine multiple injections, while this effect was not observed in CDCA treated mice. It was throught that the inhibitiory effects of hepatic glutathione decrease in morphine-treated mice by UDCA and CDCA showed a tendency of inhibitory effects of development of morphine tolerance and dependence.     

Differential modification of morphine and methadone dependence by interferon alpha

Subcutaneous implantation of a pellet of methadone was presented as a novel method for the establishment of physical dependence upon this agent and it was compared to (1) the state of physical dependence induced by multiple injections of methadone, administered over several days, and (2) the dependence established by injections of morphine and the implantation of a morphine pellet. Comparable signs of drug dependence were observed in rats treated with both morphine and methadone following the administration of the opiate antagonist naloxone. The administration of interferon-alpha significantly attenuated the severity of the withdrawal syndrome in dependent rats after chronic exposure to morphine and to a lesser extent after morphine and methadone in combination. In contrast, alpha interferon did not affect 6 of the 7 abstinence signs in animals dependent upon methadone alone. The observations suggest that the states of physical dependence upon morphine and methadone may be separate phenomena that involve different physiological mechanisms. Thus, interferon may be a useful adjunct in the treatment of subjects dependent upon morphine but not in those dependent on methadone.     

纳屈酮对吗啡和海洛因产生依赖的影响

本文观察了纳屈酮对吗啡和海洛因在大、小鼠产生依赖的影响。纳屈酮2.0-4.0mg·kg~(-1)或1.8-3.6mg·kg~(-1)po分别可对抗吗啡和海洛因在小鼠产生身体依赖;1.0-3.0mg·kg~(-1)sc可拮抗吗啡致小鼠条件性位置偏爱的形成。当吗啡诱发小鼠条件性位置偏爱形成后,纳屈酮可加速其消退。提示纳屈酮对小鼠吗啡精神依赖的产生和消退有一定影响。参考上述实验结果和人与动物间剂量折算,我们认为小剂量纳屈酮10-15mg·d~(-1)po防止阿片依赖病人戒毒后复吸是可行的。     

The effects of naltrexone on the development of physical dependence on morphine

A single i.p. injection of naltrexone (20 mg/kg) partially inhibited the development of physical dependence upon morphine in mice rendered dependent on morphine by implantation of a pellet containing 75 mg of morphine free base for three days. This was evidenced by an increase in the dose of naloxone (ED50) required to precipitate withdrawal jumping response. The increase in naloxone ED50 was much more pronounced when naltrexone was given prior to and during the course of pellet implantation. Inhibition was also observed when naltrexone was administered one day after the morphine pellet implantation, i.e., after some dependence had already developed. Naltrexone administration prior to and during the development of dependence also inhibited, but only partially, the loss of body weight and hypothermic response observed during abrupt withdrawal of morphine in morphine-dependent mice. The inhibitory effect of naltrexone on morphine dependence development was not associated with changes in brain morphine concentration.     

Effect of morphine and naloxone on intestinal transit in mice

Morphine caused a dose-dependent slowing of the rate of intestinal transit in mice. This inhibitory effect of morphine was antagonised by naloxone administration. Pretreatment with a single dose of morphine did not induce any detectable tolerance to the inhibitory effect of a second dose of morphine given 5 h later. However, naloxone was more effective in antagonising this inhibitory effect of morphine-pretreated mice than in saline-pretreated animals. Molecular sieve morphine pellet implantation for 24 h induced detectable tolerance to the inhibitory effect of morphine administered 3 h after removal of the pellet. In addition, the antagonistic effect of naloxone was also augmented when compared with blank pellet-implanted control animals. The present study has shown that the enhanced naloxone potency against the inhibitory effect of morphine on intestinal transit was observable before the development of overt tolerance, and that tolerance to the effect of morphine on the small intestine could be induced by implantation of a molecular sieve morphine pellet for 24 h.