A study on drug dependence using fast acting drugs]

Physical dependence on narcotics is induced in laboratory animals by intermittent parenteral administration (2 approximately 3 times daily). However, inducing of dependence on pethidine has been unsuccessful using the parenteral method. Recently, it has been reported that physical dependence on pethidine can be induced by continuous infusion methods (5.6). In the present experiment, pethidine was administered to rats (n=5 approximately 6) by ingestion of pethidine-admixed food preparations (0.5 approximately 4.0 mg/g of feed). The results indicated that (a) when rats are allowed free access to two food preparations (0.5 mg/g vs. 1 mg/g of food) for 7 weeks, spontaneous intake ratios of food (1 mg/g of food) gradually increased from 15% to 30% after 3 weeks. (b) Abrupt withdrawal for 48 hr after a 10 day administration period (2 mg/g of food on day 1 approximately 3 and 4 mg/g of food on day 4 approximately 10) resulted in a loss of body weight in the next 24 hr, and the prewithdrawal level of body weight was recovered in 48 hr. (c) The time course of body weight and food intake during the first 24 hr withdrawal period demonstrated the characteristic pattern of abstinence syndrome of pethidine, viz. early onset (12 approximately 13 hr) and rapid recovery (within 48 hr), as compared to morphine withdrawal. (d) Suppression of pethidine abstinence of both a single injection of morphine (10 mg/kg, s.c.) and substitution for morphine-admixed food was also realized. (e) When levallorphan (5 mg/kg, s.c.) was administered to both pethidine and morphine dependence rats, the maximal decrease in body weight was less than that in morphine dependent rats. These data indicate that pethidine possesses about one fifth the dependence liability of morphine and the maximal abstinence syndrome appears within 24 hr after withdrawal. Conclusively, application of a drug-admixed food preparation in drug dependence tests in rats has proven to be a useful method, particularly in the case of pethidine-like drugs which rapidly disappear from the blood.     

Changes in the osmotic fragility of erythrocyte membrane in morphine- and phenobarbital-dependent rats (author's transl)]

This is apparently the first attempt to elucidate the relationship between drug dependence and the osmotic fragility of erythrocyte membrane. The osmotic fragility was measured using a coil planet centrifuge (CPC) system. Utilizing the drug-admixed food (DAF) method, rats were made drug-dependent. The osmotic fragility of morphine-dependent rats was significantly enhanced, compared with that of naive rats. By withdrawing or treating the rats with levallorphan, the osmotic fragility was enhanced more than in the morphine-dependent state. When the morphine-withdrawal rats were again given the morphine-admixed food, the osmotic fragility recovered to the morphine-dependent level. The osmotic fragility of phenobarbital-dependent rats was significantly decreased, compared with that of naive rats. On the contrary, in the phenobarbital-withdrawal rats, the osmotic fragility was significantly enhanced, compared with that of the phenobarbital-dependent rats. With re-treatment of phenobarbital-admixed food, the osmotic fragility was recovered to the levels seen in the phenobarbital-dependent rats. Abstinence signs including weight loss, decrease in food and water intake, adrenal hypertrophy etc., were observed during morphine or phenobarbital withdrawal. The effects of food or water deprivation and application of ACTH on the osmotic fragility were then studied and we found that the osmotic fragility was enhanced with these treatments. These results suggest that enhancement of osmotic fragility during withdrawal of these drugs is partly influenced by these treatments.     

Preferences for opioids by the weight pulling method in rats

The preference for morphine and codeine was studied by means of the antagonistic conflict behavior between the positive drive of drug intake and the negative drive of weight pulling in rats. An apparatus was developed in which rats were compelled to pull the weight for the intake of drug-admixed food. The experiments began with the preadministration of the drug through the repetition of CFF schedule. The schedule consisted of one choice trial between the intake of normal food and drug-admixed food followed by two consecutive forced trials, in which the rats were forced to take the drug-admixed food only. In the test trial, the findings were that the rats which had already shown a drug seeking behavior toward morphine or codeine pulled weight to take each drug and that the reinforcing effects of these drugs on the drug seeking behavior depended on the treatment period of these drugs. The reinforcing effect of codeine was weaker than one of morphine. It is suggested that the reinforcing effects of these opioids can be evaluated quantitatively by the weight pulling method in rats.     

Dependence on and preference for morphine. (III) Improvement of spontaneous drug intake after combined treatment with morphine and cocaine]

One group of rats (n equals 6) was allowed free access to food combined with morphine and cocaine for 3 weeks, another group combined with either morphine or cocaine alone for 3 weeks. Intensity of decrease in body weight by withdrawal and ratios of spontaneous morphine and cocaine intake were compared, and the cross-spontaneous drug intake between morphine and cocaine using cocaine and morphine dependent rats was investigated, respectively. The results indicate that (a) decreased rate in body weight by withdrawal after 3 weeks administration with morphine-cocaine mixtures increased slightly, and spontaneous intake ratio for the higher drug-admixed food during administration period was also slightly increased as compared with a morphine added diet alone. (b) However, spontaneous intake ratio of both morphine [morphine (1 mg/g of food) vs. a normal diet (N.D.)] and cocaine [cocaine (2 mg/g of food) vs. N.D] increased 30 and 50 approximately 60% respectively, and these changes were maintained for about two months. (c) Spontaneous cocaine intake ratio after 3 weeks administration of morphine was almost the same level as that in cocaine dependent rats and decreased dependently when the administration period was extended. Spontaneous morphine intake ratio after 3 weeks administration of cocaine was 20% lower in total daily intake ratio as compared to morphine dependent rats, but spontaneous morphine intake ratio as compared to morphine dependent rats was gradually increased as in morphine dependent rats. (d) Furthermore, morphine-quinine combined treatment and cocaine or codeine treatment had no effect on spontaneous intake of quinine. These data suggest that combinations of morphine and cocaine have promoting properties of morphine and cocaine intake, respectively. Cross-spontaneous drug intake between morphine and cocaine was successful only in cocaine dependent rats using this method.     

Aspects of abstinence after morphine ingestion

Sprague-Dawley male rats were intoxicated with morphine, using an ingestion method where exposed and control rats received equivalent amounts of calories and nutrients. The degree of physical dependence on morphine was demonstrated by studying and quantifying abstinence symptoms after withdrawal or after administration of opiate antagonists. The aims of the study were (1) to further enlighten the specificity and validity of the intoxication method concerning physical dependence, and (2) to determine whether some of the abstinence signs might be of value to facilitate quantitation of the degree of physical dependence on morphine, with diet and fluid intake being maintained under control. Withdrawn rats showed a decreased fluid diet intake and a body weight loss, the latter partly due to anorexia. Other mild abstinence signs were irritation, tremor and some motor excitation. The body weight loss during the first day of morphine withdrawal was proportional to the accumulated drug dose (between 25 and 300 mg morphine PO/kg b.wt.). However, prolonged morphine treatment on one dose (340 mg/kg b.wt.) did not reinforce the body weight changes caused by morphine withdrawal. The succeeding weight gain some days after morphine withdrawal was not entirely dependent on the amount of fluid diet intake. Methadone was shown to partially block the decrease in diet intake and the weight loss seen during morphine withdrawal. The naloxone-precipitated withdrawal symptoms were motor excitation, cholinergic signs, body weight loss, diarrhoea and decreased diet intake. The weight loss 2 hr after naloxone administration to long-term intoxicated rats was proportional to the naloxone dose.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mode of antagonistic action of levallorphan in morphine-dependent rats and assessment of physical dependence liability

The antagonistic mode of levallorphan in rats dependent on morphine or codeine was studied from the viewpoints of the doses of morphine and the lengths of administration and also from the standpoint of timing of the challenge. In morphine-dependent rats on morphine-admixed food (60--100 mg/kg/day) for 1, 3 and 6 weeks, the rate of maximum weight loss on application of levallorphan (2 mg/kg, s.c.) did not correlate with the length of morphine treatment. The rate of weight loss on single application of levallorphan 0, 6, 12 or 24 hours after withdrawal or morphine was lower with the passage of time after the withdrawal. Rats which were given levallorphan 3 times in succession, i.e., at 0, 5 and 10 hours after morphine withdrawal showed such a pattern of weight loss that the first application of levallorphan resulted in 7% loss, while with the second and third applications there was little weight loss. Despite the continued withdrawal, the animals began to gain body weight as early as 14 hour, and body weight was totally recovered before the withdrawal in 24 hour. In conclusion, it is advisable to challenge with levallorphan at 0 hour of withdrawal to obtain qualitative and reproducible results. In addition, the application of levallorphan to morphine-dependent rats at adequate intervals provides for the early recovery of abstinence signs.     

Opiate dependence produced by ad libitum drinking of morphine in water,saline, and sucrose vehicles

Rats were given ad libitum morphine water, saline morphine, or sucrose morphine as their only source of liquid. Measures of liquid, food, caloric, and morphine intake along with body weight were taken daily, thereby monitoring the effects of morphine ingestion on these indices, and observing the course of dependence over time. To assess the degree of dependence the animals were given a two-bottle choice test between the drug solution and the vehicle, following a suitable ingestion period. The results indicated that the rats neglected morphine water and saline morphine in favor of the drug-free alternative. Concomitant morphine withdrawal signs (body weight loss, anorexia, adipsia, rhinorrhea, diarrhea, and irritability) were observed, thus indicating the animals were drug dependent. When morphine was given in sucrose solutions, the rats showed a marked preference for the drug solution over the vehicle.This work was supported by NSF research grants B023365 and P2B0349, and funds from the Graduate School of the University of Wisconsin-Milwaukee to K. A. Khavari.     

掺食法建立小鼠安定身体依赖性模型

本文以掺食法递增安定剂量由0.25%、0.5%至0.75%,喂食56 d,形成小鼠身体依赖性模型,进食安定的剂量高达2000 mg·kg~(-1)·d~(-1),戒断后10 h出现一系列的戒断症状,在饮食减少同时伴有体重的下降,二者与未戒断组相比均有显著性差异,而饮水量在戒断后反有增加.戒断后电惊厥率明显上升,以戒断后12 b为最显著达70%.喂食安定7 d组,戒断时亦可见轻度戒断症状,但电惊厥率与对照组相比无显著性差异.     

Suppression of the drug-induced morphine withdrawal syndrome by cyproheptadine

In rats treated with gradually increasing amounts of morphine hydrochloride until they tolerated fatal doses, levallorphan precipitated acute body weight loss and elicited a variety of other typical withdrawal symptoms. Cyproheptadine markedly reduced this b.w. loss and abolished the drug-induced withdrawal syndrome. Fenfluramine also suppressed the major signs of the levallorphan-induced morphine withdrawal; however the combination of the three drugs proved to be very toxic. Since both agents interfere with different hypothalamic feeding mechanisms these results are accordant with the hypothesis of Kerr and Pozuelo (1971) that morphine dependence and tolerance are due to a functional disorganization of the hypothalamic centers concerned wit the regulation of food intake.     

Assessment of morphine-type physical dependence liability in mice using the drug-admixed food method

Physical dependence on morphine-type drugs (morphine, codeine and pethidine) in mice were examined by the drug-admixed food method. Mice were treated with drug-admixed food of increasing concentration (1, 2 and 3 mg/g food) every third day for 9 days. Morphine- and codeine-treated mice showed withdrawal signs when they were given naloxone (5 mg/kg, s.c.), while pethidine-treated mice did not show the withdrawal signs. However, mice treated with pethidine-admixed food (1-6 mg/g food) for 28 days showed naloxone precipitated withdrawal signs. Thus, the data obtained with mice indicate that pethidine produces a weak physical dependence. On the other hand, codeine (40 mg/kg, s.c.) and pethidine (100 mg/kg, s.c.) administration suppressed the abrupt withdrawal signs of morphine-dependent mice that were treated with morphine-admixed food, while the withdrawal signs were completely suppressed in mice administered only 5 mg/kg morphine. These results suggest that the physical dependence liability of morphine type drugs can be predicted by the drug-admixed food method.     

Morphine dependence and preference. (I). Morphine preference in naive and morphine-experienced rats]

The spontnaeous morphine intake ratio (M-SIR) under free access to morphine-admixed food and quinine-admixed food conditions was measured for 3 weeks in naive and morphine-experienced rats. In the case of morphine (0.5 mg/g of food) vs. quinine (0.5 mg/g of food), naive rats gradually increased M-SIR from 17% to 77%. Using a higher level of morphine- and quinine-admixed food (1 mg/g vs. 1 mg/g of food), M-SIR was more rapidly increased than that in the lower group. Thus while on the 10 approximately 60 mg/kg/day dose range, the M-SIR was gradually increased dose dependently in naive rats due mainly to the positive reinforcing properties of morphine. Morphine-experienced rats showed a significant increase in M-SIR for the first 4 days specifically as compared with naive rats. Morphine dependent rats thus obtained morphine in sufficient amounts to maintain dependent states only after the first 2 approximately 3 days. This choice behavior revealed the psychological aspects of morphine dependence in rats and the preference for morphine was also observed after withdrawal for more than 2 weeks as secondary abstinence syndrome.     

盐酸二氢埃托啡依赖性潜力的进一步探讨

盐酸二氢埃托啡(DHE)是一种新的强效麻醉性镇痛药,本文着重对DHE在啮齿类动物Do及舌下给药条件下的自然戒断,替代吗啡,催促戒断等方面的致依赖性潜力进行了研究,结果表明,DHE的致身体依赖性潜力确实较低;以DHE替代吗啡抑制阿片类戒断症状时舌下给药剂量低于po给药剂量;在一定剂量条件下DHE舌下给药可使实验动物对其产生身体依赖性。     

Morphine dependence in rats produced after five days of ingestion

In the first experiment dose-dependent withdrawal signs following a nalorphine injection (either 2, 4, 8, 16, or 32 mg/kg, i.p.) were seen in rats that had been drinking sucrose morphine for 21 days. A non-dependent control group was generally unaffected by an injection of the antagonist (16 mg/kg, i.p.). In Experiment II, morphine withdrawal signs, both nalorphine induced and without nalorphine injection, were observed in rats which had been placed on only five days of morphine-adulterated food and sucrose morphine. Although both groups showed clear withdrawal signs after the drug was removed from their diet, the nalorphine-injected group showed more severe symptoms. By the eleventh day of withdrawal all rats had resumed normal eating and drinking and had nearly recovered their pre-drug body weights. It is concluded that reliable morphine dependence can be induced in five days, using a morphine-adulterated diet.This work was supported by NSF research grants B023365 and P2B0349 to K. A. Khavari.     

Physical dependence liability test of ifenprodil in rats (author's transl)

A single administration of ifenprodil at the doses of 100, 200 and 400 mg/kg (p.o.), and 50 and 100 mg/kg (i.m.) produced a moderate CNS depression in rats, such as, sedation, ptosis, systemic muscle relaxation and decrease in motor activity. These symptoms appeared dose-dependently and persisted for about 4 hours following administration. In a direct physical dependence test, 5 groups of rats were fed the ifenprodil-admixed food together with drinking water ad libitum for 24 hours daily for 53 approximately 103 days (mean ifenprodil intake, 43--240 mg/kg/day), on the gradedly increased dosage schedule with a dosage level of 0.5 vs. 1 mg/g food to 4 mg/g food. In the natural withdrawal following administration, no significant withdrawal signs were observed in any group. In a substitution test either for phenobarbital or morphine, no suppression of withdrawal signs during the period of cross-administration of ifenprodil and no maintenance of dependence were observed. In a physical dependence-producing test, the rats fed ifenprodil never manifested withdrawal signs such as diarrhea, "wet shakes", sudden loss of body weight as in the levallorphan precipitation test. Ifenprodil apparently has no physical dependence liability.     

Comparison of development of drug dependence in naive and drug dependence-experienced rats]

Phenobarbital, chordiazepoxide, diazepam and/or morphine were repeatedly administered to both male and female rats (N equals 10) for 4 similar to 6 weeks. The drug dose was gradully increased from 5 to 10, 20, 40, 80 and 160 mg/kg once daily (p.o) at seven day intervals. In the case of morphine, the last dose was 40 mg/kg. The drugs were constantly withdrawn for 24 hr at 8 day intervvals. None of the rats were given drugs for 16 days after administration of the last scheduled dose in order to recover their initial weight (Exp. I). Onset of dependence formation, decrease in body weight and food intake, days required to reach the maximum decrease in body weight and duration of withdrawal signs were observed throughout this experiment. The rats (drug dependence-experimented rats) who survived the first stage of this experiment were continuously subjected to re-administration by the same dosage schedule as in Exp. I (seven days of drug administration, 48hr of withdrawal). The re-administered rats showed a more rapid onset of dependence formation and a longer duration of decreas in boy weight during 16 days withdrawal than did the naive rats. It is concluded, that in addition to the decrease in body weight by withdrawal plus duration of the withdrawal signs, the onset of drug dependence formation is also a specific factor.     

A method for computer control of morphine ingestion by rats

In this paper, we describe a method for controlling the administration of liquid diet and morphine to sixteen rats using a computer. Morphine ingestion treatment was performed with 6 feeding occasions per 24 hr, all experimental animals receiving similar drug doses. The amount of drug was individual and based on body weight at each feeding occasion. Control and experimental animals were kept under isocaloric conditions. Corrections of drug doses in order to compensate for changes in body weight were made every 24 hr. Sensors registered the exact time of complete drug and diet consumption and prevented overdistribution. Rats were administered 103 mg/kg b.wt. morphine during 24 hr. In another experiment rats were administered 191 mg/kg b.wt. morphine during 48 hr, and no weight loss or decrease in fluid diet intake was registered during the time of drug administration in either of the experiments. After exclusion of morphine from the fluid diet, the body weight loss was 6.1% and 8.3%, respectively, and the liquid diet intake decreased by 12.4 ml and 13.4 ml, respectively, compared with control animal intake. This demonstrates the induction of physical drug dependence. A major advantage of using computer-aided administration of morphine-admixed, fluid diet is the stepwise, small dose increments provided several times a day, resulting in higher drug dose per unit time when compared with ingestion procedures using one feeding occasion per day. The method enables rats to rapidly ingest large morphine doses under standardized conditions.     

Sex differences in the induction of physical dependence on pentobarbital in the rat

Sex differences in physical dependence on sodium pentobarbital in the rat were studied by the drug-admixed food (DAF) method. With male rats, the concentration of pentobarbital in the food was gradually increased from 2 to 30 mg/g over a period of 50 days. The final level of drug intake was approximately 1.7 g/kg/day. At pentobarbital concentrations of 20 and 22 mg/g of food, sedation and mild muscle relaxation were observed. At the highest drug concentration, 30 mg/g of food, marked muscle relaxation was noted. With female rats, the concentration of pentobarbital in the food was gradually increased from 1 to 16 mg/g over a period of 47 days. The final level of intake was approximately 1.0 mg/kg/day. At drug concentrations of 12 and 14 mg/g, sedation and mild muscle relaxation appeared. At 16 mg/g, female rats showed marked muscle relaxation similar to that of the male rats. To produce severe loss of muscle tone, the male rats required twice as much pentobarbital as the female rats. After substitution of normal food for the pentobarbital-admixed food, various signs of pentobarbital withdrawal occurred in both sexes. These signs included vocalization, irritability, muscle rigidity, tremors and convulsions. Onset of withdrawal was more rapid in the females, and the maximum weight loss was greater, 8.0% compared to 3.8% in the males. Physical dependence on pentobarbital was easily developed in both sexes by the DAF method. There was a marked sex difference in withdrawal which we attribute to sex differences in drug metabolizing enzyme activity.     

Effects of morphine on brainstem neurones in naive and chronic morphine-treated rats, and effects of PCPA.

Rats were made dependent on morphine by adding the drug to both their food and drinking water for 7 days. Following withdrawal of morphine after 5 days of exposure, obvious abstinence effects were seen. Responses of brain stem neurones to microiontophoretically applied morphine were examined in rats after chronic exposure to morphine, as well as 48 hr after withdrawal. These responses were compared with those obtained in naive control rats. Although the overall responsiveness towards morphine was not affected by 7 days morphine exposure, a small reduction in the proportion of morphine-induced depressions was observed in chronic morphine-treated rats compared with naive controls. Withdrawn animals did not show this difference. Chronic morphine treatment also increased the frequency of occurrence of naloxone-induced excitation. Pretreatment with PCPA reduced the overall responsiveness of naive animals to morphine but combined with chronic morphine treatment it also increased the proportion of morphine excitations.     

Withdrawal from chronic, intermittent access to a highly palatable food induces depressive-like behavior in compulsive eating rats

The increased availability of highly palatable foods is a major contributing factor toward the development of compulsive eating in obesity and eating disorders. It has been proposed that compulsive eating may develop as a form of self-medication to alleviate the negative emotional state associated with withdrawal from highly palatable foods. This study was aimed at determining whether withdrawal from chronic, intermittent access to a highly palatable food was responsible for the emergence of depressive-like behavior. For this purpose, a group of male Wistar rats was provided a regular chow diet 7 days a week (Chow/Chow), whereas a second group of rats was provided chow for 5 days a week, followed by a 2-day access to a highly palatable sucrose diet (Chow/Palatable). Following 7 weeks of diet alternation, depressive-like behavior was assessed during withdrawal from the highly palatable diet and following renewed access to it, using the forced swim test, the sucrose consumption test, and the intracranial self-stimulation threshold procedure. It was found that Chow/Palatable rats withdrawn from the highly palatable diet showed increased immobility time in the forced swim test and decreased sucrose intake in the sucrose consumption test compared with the control Chow/Chow rats. Interestingly, the increased immobility in the forced swim test was abolished by renewing access to the highly palatable diet. No changes were observed in the intracranial self-stimulation threshold procedure. These results validate the hypothesis that withdrawal from highly palatable food is responsible for the emergence of depressive-like behavior, and they also show that compulsive eating relieves the withdrawal-induced negative emotional state.     

Some altered responses in rats formerly dependent on morphine

This investigation examined whether or not physical dependence or other abnormalities were detectable 1–3months after withdrawal in dependent rats that had been treated with the morphine (maintenance dose of 100×2mg/kg/day,s.c.) for 7 weeks. When narcotic antagonists were administered on the 32nd day after withdrawal, nalorphine caused a dose-dependent increase in spontaneous locomotor activity and a complete inhibition of wet-dog shakes and the writhing syndrome. Naloxone was ineffective. A remarkable increase in spontaneous locomotor activity on the 67th day and a significant increase in body weight on the 69th and 92nd day after withdrawal occurred after an acute injection of morphine (10 mg/kg, s.c.). When morphine (10 mg/kg) was administered for 3 days from the 92nd day after withdrawal, withdrawal from morphine produced a significant decrease in body weight. When morphine (10 mg/kg) was administered for 3 days from the 102nd day after withdrawal, a levallorphan injection caused a significant decrease in spontaneous locomotor activity and an increase in the frequency of the diarrheal syndrome. These abnormal responses, not observed in the naive rats, suggest the remains of some behavioral and biochemical abnormalities 3 months after morphine withdrawal.Part of this work was presented at the 4th Symposium on Drug-Activity held in Nagasaki, Japan, 30–31st October 1975