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  • 1
    Electronic Resource
    Electronic Resource
    Conditioned temperature effects using morphine as the unconditioned stimulus (1979)
    Springer
    Psychopharmacology 61 (1979), S. 31-38 
    Details
    ISSN: 1432-2072
    Keywords: Conditioning ; Morphine ; Body temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The conditioning of body temperature changes using an injection of morphine sulphate as the conditioned stimulus was studied in 30 male Wistar rats. Three groups of animals received daily i.p. injections of either 5, 25, or an increasing dose to 200 mg/kg morphine; a fourth group received saline injections throughout. Rectal temperature was measured in three different environments five times during the day: in a neutral environment, the home cage; in a pre-injection environment, in which animals were placed for a period before the daily injection; and in an injection environment, in which animals remained after the injection. Conditioning trials were followed by a period of abstinence from morphine. Tests for conditioned effects were carried out both during conditioning and after the period of abstinence. During conditioning, animals in the morphine groups, when compared to the saline control animals, showed a conditioned anticipatory hypothermia in the preinjection environment that was opposite in direction to the unconditioned hyperthermia to morphine. In contrast, in the injection environment, animals in the morphine groups showed a conditioned hyperthermia when tested after the period of abstinence. These results suggest a complex interaction between the conditioned and unconditioned temperature responses to morphine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00426807
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  • 2
    Electronic Resource
    Electronic Resource
    Temporal and environmental cues in conditioned hypothermia and hyperthermia associated with morphine (1981)
    Springer
    Psychopharmacology 72 (1981), S. 147-153 
    Details
    ISSN: 1432-2072
    Keywords: Conditioning ; Morphine ; Body temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effectiveness of temporal and environmental cues in eliciting conditioned hypothermia and hyperthermia was studied in male Wistar rats using as an unconditioned stimulus an IP injection of 20 mg/kg of morphine sulfate. The relevance of temporal stimuli was minimized in Experiment 1 by administering morphine at irregular times on alternate days. For one group (Cond) morphine injections were preceded and followed by periods in distinctive environments. Group Pseudo animals, though exposed to the environments, received morphine on the intervening days in the home cage; group Saline received only saline. All animals receiving morphine showed a non-specific hypothermia when not under the direct influence of morphine. A “conditioned hyperthermia” was evident in group Cond animals in the distinctive environments. In Experiment 2, in which animals remained in their home cages at all times, the releavance of temporal cues was emphasized by administering morphine at exactly 24 h intervals. These animals became hypothermic only around the time of the expected injection. Animals in another group that received morphine at irregular times showed the non-specific hypothermia seen previously. There was no evidence for a conditioned hyperthermia in this second experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00431648
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Temporal factors in the effect of restraint stress on morphine-induced behavioral sensitization in the rat (1995)
    Springer
    Psychopharmacology 117 (1995), S. 102-109 
    Details
    ISSN: 1432-2072
    Keywords: Conditioning ; Locomotor activity ; Morphine ; Mesocorticolimbic dopamine system ; Opioids ; Stress ; Ventral tegmental area
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The role of associative factors in the effect of 15 min/day of restraint stress on morphine-induced behavioral sensitization was examined. Male rats were initially given seven systemic (10 µg/kg, IP) or intraventral tegmental area (VTA, 5 mg/side) injections of morphine, and were exposed to restraint, either just prior to drug injection (Paired-Stress) or 24 h after injection (Unpaired-Stress), or to no restraint (Control). In subsequent tests for behavioral sensitization to low doses of morphine (0.75 or 3.0mg/kg, IP), animals in the Paired-Stress condition were more active than animals in the Unpaired-Stress or Control conditions. These results indicate that temporal and possibly associative factors may contribute to stress-induced changes in sensitization to the behavioral activating effects of opioids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245104
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  • 4
    Electronic Resource
    Electronic Resource
    Acamprosate suppresses the expression of morphine-induced sensitization in rats but does not affect heroin self-administration or relapse induced by heroin or stress (1998)
    Springer
    Psychopharmacology 139 (1998), S. 391-401 
    Details
    ISSN: 1432-2072
    Keywords: Key words Acamprosate ; Dopamine ; Heroin self-administration ; Nucleus accumbens ; Reinstatement ; Relapse ; Sensitization ; Stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Acamprosate (calcium-acetyl homotaurinate) is a new compound used in the treatment of alcohol abuse. Because of the putative link between alcoholism and the endogenous opioid systems in both humans and laboratory animals, we tested in rats the effects of acamprosate on behavioral and neurochemical effects of opioid drugs related to their abuse potential. These included sensitization to the behavioral effects of morphine, morphine-induced dopamine (DA) release in the nucleus accumbens (NAS), intravenous (IV) heroin self-administration and relapse to heroin seeking in drug-free rats. In experiment 1, rats were injected daily with either morphine (10 mg/kg, SC) or saline for 14 days. Three days later in a test for the expression of sensitization, an injection of morphine (10 mg/kg) resulted in increased locomotor activity and enhanced DA release in the NAS in rats previously exposed to morphine. Acamprosate (two injections of 200 mg/kg; 12 h apart; IP) suppressed the expression of the sensitized responses, but did not alter the effects of morphine in drug-naive control rats. In experiment 2, it was found that acamprosate (two injections of 50–200 mg/ kg; IP) had no consistent effects on IV heroin self-administration (50–100 μg/kg per infusion) and, in experiment 3, that acamprosate (100–200 mg/ kg, IP) did not alter reinstatement of drug seeking induced by priming injections of heroin (0.25 mg/kg, SC) or a footshock stressor (15 min; 0.5 mA) after a 5- to 8-day period of extinction. Thus, although acamprosate attenuated the expression of sensitized locomotor activity and DA release in the NAS, it did not have any consistent effect on either the intake of heroin during the maintenance phase or the relapse to heroin seeking in a drug-free state. Thus, to the extent that the self-administration and the reinstatement procedures provide valid preclinical models for drug use and relapse in humans, our data suggest that acamprosate may not be effective in altering drug-taking behavior in heroin users.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050730
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    CP-154,526, a selective, non-peptide antagonist of the corticotropin-releasing factor1 receptor attenuates stress-induced relapse to drug seeking in cocaine- and heroin-trained rats (1998)
    Springer
    Psychopharmacology 137 (1998), S. 184-190 
    Details
    ISSN: 1432-2072
    Keywords: Key words Cocaine ; Corticotropin-releasing factor ; CRF receptor ; Drug self-administration ; Heroin ; Reinstatement ; Relapse ; Stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have found that peptide antagonists of corticotropin-releasing factor (CRF) receptors attenuate reinstatement of heroin and cocaine seeking induced by footshock. Here we examined the effect of a non-peptide, selective CRF1 receptor antagonist, CP-154,526, on reinstatement of heroin and cocaine seeking induced by footshock. Rats were trained to self-administer heroin or cocaine (0.1 and 1.0 mg/kg per infusion, IV, respectively) for 9–12 days. Extinction sessions were given for up to 14 days, during which saline was substituted for the drugs. Tests for reinstatement were then conducted after exposure to intermittent footshock (10 or 15 min, 0.5 mA). The footshock stressor reliably reinstated extinguished cocaine- and heroin-taking behavior. Pretreatment with CP-154,526 (15 and 30 mg/kg, SC) significantly attenuated the reinstatement effect of the stressor in both heroin- and cocaine-trained rats. CP-154,526, administered in the absence of the footshock stressor, did not affect extinguished drug seeking. In addition, in a separate experiment, CP-154,526 was shown not to alter high rates of lever pressing for a 10% sucrose solution, suggesting that the suppression of lever pressing in stress-induced reinstatement is not caused by a performance deficit. These results extend previous reports on the role of CRF in reinstatement of drug seeking induced by stressors. The present data also suggest that, to the extent that exposure to environmental stressors provoke relapse to drug use in humans, systemically effective CRF receptor antagonists may be of use in the treatment of relapse to drug use.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050608
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Exposure to mild stress enhances the reinforcing efficacy of intravenous heroin self-administration in rats (1994)
    Springer
    Psychopharmacology 114 (1994), S. 523-527 
    Details
    ISSN: 1432-2072
    Keywords: Heroin ; Intravenous drug self-administration ; Opioid drugs ; Progressive ratio ; Stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of a mild footshock on intravenous heroin self-administration was examined in male rats. Animals in the stress condition were exposed to 10 min of intermittent footshock (0.5 mA; 0.5 s on, with a mean off period of 40 s) before each of four daily self-administration sessions. Animals in the control group were not exposed to footshock. Following acquisition of heroin-reinforced behavior (100 µg/kg per infusion), during which no group differences emerged, animals were placed on a progressive ratio schedule of reinforcement and were subsequently tested under a decreasing series of doses. Animals exposed to footshock before each drug session had higher rates of lever pressing for heroin and achieved higher final ratios on the progressive ratio schedule than animals in the control group at the higher doses of heroin. Thus, under the conditions of this experiment, exposture to mild intermittent stress appeared to enhance the reinforcing efficacy of heroin. The parameters of footshock used in the present study, and its relation to drug availability may characterize conditions under which stress leads to increased opioid abuse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02249346
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    Paper (German National Licenses)
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