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  • 42.65  (2)
  • Dopamine  (2)
  • Withdrawal  (2)
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  • 1
    Digitale Medien
    Digitale Medien
    Potentiation of the effects of reward-related stimuli by dopaminergic-dependent mechanisms in the nucleus accumbens (1991)
    Springer
    Psychopharmacology 104 (1991), S. 377-385 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Conditioned reinforcement ; Dopamine ; Noradrenaline ; d-Amphetamine ; Dorsal noradrenergic bundle ; Nucleus accumbens
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Three experiments examined the behavioural, pharmacological and neural specificity of the previously reported potentiation of responding with conditioned reinforcement following intra-accumbensd-amphetamine, by studying the effects of intraaccumbens dopamine (DA) and noradrenaline, using an acquisition of a new response procedure. In experiment 1, the effects of intra-cerebral DA infusions (5, 20, 50 µg/2 µl) were compared in four conditions: (i) intra-accumbens DA following positive pairing of the conditioned stimulus (CS) and water during training; (ii) as (i) but also following a systemic dose of the DA receptor antagonist alpha-flupenthixol; (iii) intra-accumbens DA following random pairing of the CS and water during training; and (iv) as (i) but with intra-caudate rather than intra-accumbens DA. The results showed that only with intra-accumbens DA in the positive pairing condition was there a significant dose-dependent increase in responding. In experiment 2, the effects of a higher range of doses (20, 100, 200 µg) and smaller infusion volume (5, 25, 50 µg/l µl) of intra-accumbens DA were studied, in comparison with a similar range of doses (5, 25, 50 µg/l µl) of intra-accumbens noradrenaline (NA). Only DA produced a selective, dose-dependent increase in responding with conditioned reinforcement. In experiment 3 neurotoxic lesions of the dorsal noradrenergic bundle (DNAB) using 6-hydroxydopamine producing profound (about 90%) depletion of cortical and nucleus accumbens NA levels had no effect on the increased responding with conditioned reinforcement produced by intra-accumbensd-amphetamine (3, 10, 30 µg/l µl). The results are discussed in terms of the neurochemical mediation of the potentiation of the effects of conditioned reinforcers byd-amphetamine and the role of DA-dependent mechanisms of the nucleus accumbens in reward-related processes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02246039
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  • 2
    Digitale Medien
    Digitale Medien
    Yohimbine co-treatment during chronic morphine administration attenuates naloxone-precipitated withdrawal without diminishing tail-flick analgesia in rats (1991)
    Springer
    Psychopharmacology 103 (1991), S. 407-414 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Yohimbine ; Morphine ; Naloxone ; Withdrawal ; Tail flick latency ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Noradrenergic neuronal hyperactivity following chronic morphine administration has been postulated to cause withdrawal signs and symptoms. Suppression of this hyperactivity, for example, by clonidine attenuates withdrawal. It might follow, therefore, that the prevention of suppression of noradrenergic systems during chronic morphine administration might diminish hyperactivity and prevent withdrawal. If the normalization of noradrenergic activity during opioid administration did not also suppress analgesia, it might be of medical and theoretical interest. To test this hypothesis, we gave the alpha-2-antagonist yohimbine to rats in order to increase noradrenergic activity during morphine treatment and then subsequently precipitated morphine withdrawal with naloxone. Six groups were examined: saline controls (N=11), morphine (N=11), morphine + 2.0 mg/kg/day yohimbine (N=15), morphine + 3.0 mg/kg/day yohimbine (N=5), 2.0 mg/kg/day yohimbine (N=11) and 3.0 mg/kg/day yohimbine (N=5). Subjects received 75 mg morphine pellets implanted on day 1,4 and 6 of the treatment or sham implantation. Yohimbine was delivered throughout the morphine treatment by subcutaneously implanted osmotic pumps. On day 7, all subjects were given 1.0 mg/kg naloxone and rated for behavioral signs of withdrawal. Analgesia was measured by observing tail flick latencies (TFL) before and after chronic drug treatments. Naloxone-precipitated withdrawal was characterized by irritability, ptosis, penile erection, diarrhea, rhinorrhea, abnormal posture, wetdog shakes, jumping, and teeth chattering, none of which were observed in groups receiving only saline or yohimbine. Withdrawal behavior was attenuated in a dose-dependent manner when yohimbine was administered during morphine treatment but analgesia was not attenuated. It appears that yohimbine-induced antagonism of alpha-2-adrenergic receptors diminishes the development of the potential for adrenergic hyperactivity and morphine withdrawal without reducing opioid analgesia.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02244297
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  • 3
    Digitale Medien
    Digitale Medien
    Impulsivity resulting from frontostriatal dysfunction in drug abuse: implications for the control of behavior by reward-related stimuli (1999)
    Springer
    Psychopharmacology 146 (1999), S. 373-390 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Key words Compulsion ; Addiction ; Cocaine ; Amphetamine ; Cannabis ; Phencyclidine ; Nucleus accumbens ; Amygdala ; Frontal cortex ; Limbic ; Stimulus-reward association ; Conditioned reward ; Sensitization ; Drug-seeking ; Inhibitory control ; Cognition ; Conditioned stimulus ; Incentive motivational ; Dopamine ; Rat ; Monkey
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  Drug abuse and dependence define behavioral states involving increased allocation of behavior towards drug seeking and taking at the expense of more appropriate behavioral patterns. As such, addiction can be viewed as increased control of behavior by the desired drug (due to its unconditioned, rewarding properties). It is also clear that drug-associated (conditioned) stimuli acquire heightened abilities to control behaviors. These phenomena have been linked with dopamine function within the ventral striatum and amygdala and have been described specifically in terms of motivational and incentive learning processes. New data are emerging that suggest that regions of the frontal cortex involved in inhibitory response control are directly affected by long-term exposure to drugs of abuse. The result of chronic drug use may be frontal cortical cognitive dysfunction, resulting in an inability to inhibit inappropriate unconditioned or conditioned responses elicited by drugs, by related stimuli or by internal drive states. Drug-seeking behavior may thus be due to two related phenomena: (1) augmented incentive motivational qualities of the drug and associated stimuli (due to limbic/amygdalar dysfunction) and (2) impaired inhibitory control (due to frontal cortical dysfunction). In this review, we consider the neuro-anatomical and neurochemical substrates subserving inhibitory control and motivational processes in the rodent and primate brain and their putative impact on drug seeking. The evidence for cognitive impulsivity in drug abuse associated with dysfunction of the frontostriatal system will be discussed, and an integrative hypothesis for compulsive reward-seeking in drug abuse will be presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/PL00005483
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  • 4
    Digitale Medien
    Digitale Medien
    Clonidine infusions into the locus coeruleus attenuate behavioral and neurochemical changes associated with naloxone-precipitated withdrawal (1988)
    Springer
    Psychopharmacology 96 (1988), S. 121-134 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Clonidine ; Locus coeruleus ; Intracerebral infusion ; Withdrawal ; Naloxone ; Morphine ; 3-Methoxy-4-hydroxyphenylglycol (MHPG) ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Clonidine, an alpha-2-adrenergic agonist, suppresses signs of opiate withdrawal in animals and in man. Electrical or chemical stimulation of the nucleus locus coeruleus (LC) increases noradrenergic activity and brain concentration of the noradrenergic metabolite MHPG, and produces many signs of opiate withdrawal. Thus, clonidine's ability to attenuate withdrawal might be due to the reduction of noradrenergic neuronal activity originating in the LC, but additional alpha-2-adrenergic receptors throughout the body and other mechanisms may also play a role. The present study explored the neuroanatomical and pharmacological selectivity of alpha-2-adrenergic receptors of the LC in the anti-withdrawal action of clonidine. Experiment 1 tested the hypothesis that behavioral and biochemical measures of naloxone-precipitated withdrawal from morphine would be blocked by infusions of clonidine (0.6 or 2.4 μg/μl) into the LC. Significant reductions were observed in the occurrence of diarrhea, ptosis, weight loss and wet-dog shakes. Clonidine also reversed the naloxone-precipitated increase in hippocampus MHPG concentration. In experiment 2 subjects received an LC infusion or IP injection of a non-lipophilic alpha-2-agonist (ST-91), which does not penetrate the blood-brain barrier, or of clonidine into the dorsal parabrachial nucleus (DPB) to test the selectivity of the effects of clonidine infusions into the LC. ST-91 infusions into the LC reduced several of the observed withdrawal signs and increased others (e.g., jumping). Although peripheral injections of ST-91 attenuated some of the checked signs associated with naloxone-precipitated withdrawal, the frequency of wet-dog shakes was not reduced. ST-91 infusions into the LC, but not systemic ST-91 administration, prevented the withdrawal-induced increase in hippocampus MHPG concentration. Clonidine infused lateral to the LC into the DPB did not significantly attenuate withdrawal or reduce hippocampus MHPG levels. These results provide behavioral and biochemical evidence to support the suggestion that clonidine significantly attenuates naloxone-precipitated withdrawal through an interaction with noradrenergic neurons located in the vicinity of the LC.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02431544
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  • 5
    Digitale Medien
    Digitale Medien
    Spectral and temporal study of picosecond-pulse propagation in a single-mode optical fibre (1986)
    Springer
    Applied physics 39 (1986), S. 43-46 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.10 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The power-dependent pulsewidth variations for input 85 ps pulses from a cw mode-locked Nd: YAG laser propagating through 125 m of single-mode optical fibre have been examined using a Synchroscan streak camera. Simultaneous spectral and temporal measurements provide information as to the optimum parameters for pulse compression in fibres.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00695591
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  • 6
    Digitale Medien
    Digitale Medien
    Spectral and temporal investigations of nonlinearities in a non-polarization preserving single-mode optical fibre (1986)
    Springer
    Applied physics 41 (1986), S. 235-240 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.10 ; 42.65 ; 42.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Intense green and red components generated in a non-polarization preserving optical fibre using a Q-switched and mode-locked cw Nd: YAG laser have been examined spectrally and temporally with picosecond resolution. In addition to the red (four-photon interaction) and green (second-harmonic) components, many other frequency mixing processes were detected. From theoretical considerations, the red component (anti-Stokes) which is generated through parametric four photon mixing should be in the same propagation mode as the Stokes component (ir) and this was confirmed experimentally.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00697404
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