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  • 1
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2072
    Keywords: Abuse liability ; Addiction ; Behavior ; Monkey ; Physical dependence ; Rat ; Reinforcement ; Self-administration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A total 31 psychoactive drugs were offered to groups of naive rats for IV self-administration and an injection rate greater than that for rats offered only saline indicated reinforcement. Two protocols were used: in the first, rats were offered drug at a selected dose for 5 days, then the dose was reduced by 1 log unit (to 0.1 the original dose) for an additional 4 days; in the second, rats were offered saline for 3 days as a ‘prescreen’ to eliminate rats with high or low operant-injection rates. Drug was offered to acceptable rats for 5 days, then the dose was reduced 0.5 log unit (to 0.32 the original dose) for 5 more days. A scoring system, based upon the injection rates during the last 3 days of each period, describes the reinforcing action. Scores were dose-related. Tests on both protocols gave similar results. Data from monkey studies have been reported for 27 of the drugs tested. Of these drugs, 18 were reinforcers and six were nonreinforcers in both species, nalorphine and ethylketazocine were reinforcers only in rats, and ethanol was a reinforcer only in monkeys.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 65 (1979), S. 171-177 
    ISSN: 1432-2072
    Keywords: Morphine ; Rat ; Self-administration ; Physical dependence ; Addiction ; Reinforcement ; Behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Groups of naive rats were offered morphine sulfate for self-administration in doses of 0.0032–10 mg/kg for 6 days. On day 7 saline was substituted for morphine. Loss of weight was taken as physiological evidence of dependence. Rats that did not lose weight formed a single population whose mean injection rate did not differe from control rats receiving only saline injections. Injection rates for rats losing weight were log-normally distributed, and the mean of the logarithms of the injection rates was linearly related to the logarithm of the dose. Mean daily injection rates averaged 12 for controls, 23 at 10 mg/kg, and 411 at 0.01 mg/kg. A transient increase in morphine intake after an injection of nalorphine was taken as behavioral evidence of dependence. Nalorphine increased morphine intake when rats were self-injecting 0.32 and 1.0 mg/kg of morphine, but not 0.032 or 0.1 mg/kg. The reinforcing property of morphine may occur without behavioral evidence of dependence.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 249 (1965), S. 509-514 
    ISSN: 1432-1912
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A method is described for obtaining potency estimates of narcotic analgesics to morphine in experimental addict rats. Drugs were administered through a chronic right heart cannula and intake was under the rat's voluntary control. Animals were offered two doses of morphine (3.2 and 10 mg/kg/injection) and two doses of test compound on a fixed ratio reinforcement schedule of 10:1. Logarithm of the daily number of injections taken was used as the effect metameter. Each potency estimate was based on results in four rats. Rats averaged 137 mg/kg/day of morphine when offered 10 mg/kg/injection. A diurnal variation in opiate intake was observed, the nighttime rate being about one-third greater than the daytime rate. Morphine intake measured before and after the assay period was essentially unchanged. Potency estimates and the 95% fiducial interval were: dihydromorphinone = 10 (5.2−19) × morphine, methadone = 3.4 (2.7−4.6) × morphine and codeine = 0.67 (0.45−1.0) × morphine. Analgesic activity for codeine was not proportional to its ability to substitute for morphine in addict rats.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 6 (1964), S. 267-279 
    ISSN: 1432-2072
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Self-maintained morphine addicted rats were prepared by implanting chronic venous cannulas and fitting the rats with a device permitting relatively free movement and also enabling them to obtain morphine injections at will by pressing a lever. Three factors modifying voluntary morphine intake were studied. 1. Using a continuous reinforcement schedule, progressively decreasing the size of the morphine dose led to a greater number of doses daily. Compensation was incomplete in that the total daily morphine intake decreased. 2. Progressively increasing a fixed ratio reinforcement schedule up to about FR-75, caused rats to continue responding on the lever until the dose was obtained. Above FR-75 responding became intermittent and daily morphine decreased as the time interval between doses increased. 3. Continuous intravenous infusion of a second drug, leaving voluntary access to morphine at FR-10, led to decreased morphine intake following infusion of morphine itself, codeine and meperidine. Nalorphine infusion increased morphine intake. Effectiveness of infusions varied with the infusion rate.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 11 (1967), S. 287-292 
    ISSN: 1432-2072
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Dexoxadrol, dextromethorphan and meperidine were given by continuous intravenous infusion to selfmaintained morphine dependent rats. Dexoxadrol and dextromethorphan did not significantly decrease the rate of morphine self-administration. Meperidine produced a dose related decrease in the rate of morphine injections. The failure of dexoxadrol to reduce morphine intake is evidence that it will probably not produce opioid-like addiction liability in man.
    Type of Medium: Electronic Resource
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