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  • 1
    Electronic Resource
    Electronic Resource
    Enhanced stimulus-reward learning by intra-amygdala administration of a D3 dopamine receptor agonist (1997)
    Springer
    Psychopharmacology 133 (1997), S. 240-248 
    Details
    ISSN: 1432-2072
    Keywords: Key words Stimulus-reward learning ; Discriminative approach ; Dopamine ; Amygdala ; SKF-38393 ; Quinpirole ; 7-OH-DPAT ; D3 receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The amygdala is considered to be a critical neural substrate underlying the formation of stimulus-reward associations, and is known to receive substantial innervation from dopaminergic neurons located within the ventral mesencephalon. However, relat- ively little is known about the function of the mesoamygdaloid dopamine projection in stimulus-reward learning. Recently, we have found post-session intra-amygdala microinjections of d-amphetamine to enhance appetitive Pavlovian conditioning as assessed in a discriminative approach task. In the present study, we have examined the effects of dopamine receptor agonists possessing relative selectivity for the D1, D2 and D3 receptor subtypes in order to examine more fully the role of the mesoamygdaloid dopamine projection in stimulus-reward learning. Thus, subjects were trained to associate an initially neutral stimulus (CS+) with 10% sucrose reward (US). A second, control stimulus (CS−) was also presented but never paired with sucrose reward. In order to measure specifically the conditioned response to CS+/CS− presentation, responding during CS and US presentations was measured separately. Immediately following each training session, subjects received bilateral intra-amygdala infusion of 0.1, 1 or 10 nmol/side of SKF-38393, quinpirole or 7-OH-DPAT. Infusions of SKF-38393 or quinpirole were without effect on CS+ approach. However, post-session intra-amygdala infusions of 7-OH-DPAT enhanced selectively CS+ approach in a dose-dependent fashion. No dose of any drug affected CS−approach, US behaviours, or measures of extraneous behaviour. Subsequent acquisition of a novel conditioned instrumental response was also unaffected. Thus, the present data indicate a selective involvement of the D3 dopamine receptor subtype in the modulation of stimulus-reward learning by the mesoamygdaloid dopamine projection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050397
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  • 2
    Electronic Resource
    Electronic Resource
    Enhanced acquisition of discriminative approach following intra-amygdala d-amphetamine (1997)
    Springer
    Psychopharmacology 132 (1997), S. 237-246 
    Details
    ISSN: 1432-2072
    Keywords: Key words Stimulus-reward learning ; Conditioned reward ; d-Amphetamine ; Dopamine ; Amygdala
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study examined the role of the mesoamygdaloid dopamine projection in stimulus-reward learning. Bilateral post-session intra-amygdala microinjections of d-amphetamine were carried out in rats during training in a discriminative approach task known to be sensitive to experimental manipulations of the amygdala. The experiment consisted of two phases: discriminative approach training, and a subsequent assessment of instrumental conditioned reward efficacy. During discriminative approach training, subjects were trained to associate a neutral stimulus with 10% w/v sucrose reward. Each trial consisted of a 1-s light stimulus followed by a 5-s presentation of the sucrose reward. Approach behaviour into the recess housing sucrose reward was measured during each trial. Inappropriate approach behaviour (approach outside of the trial periods) was punished by delaying the next trial. Intra-amygdala d-amphetamine (10 μg/side) enhanced the rate of acquisition of discriminative approach behaviour. This effect was most evident early during training (sessions 2–4) and by the tenth session both groups had reached similar asymptotic performance. Horizontal and vertical activity increased slightly across sessions, but there was no indication of a differential effect of d-amphetamine. Thus, intra-amygdala microinjections of d-amphetamine enhanced selectively the acquisition of the stimulus-reward association. During a subsequent test of instrumental conditioned reward, presentation of the conditioned light stimulus was made contingent upon performance of a novel lever-pressing response (probability 0.5). Responding on a second, control lever was without programmed consequences. Sucrose reward was not available at any point, and subjects were tested drug-free. In both groups the conditioned stimulus was found to possess significant conditioned rewarding efficacy. Extraneous behaviour was increased in the d-amphetamine group but the rewarding properties of the conditioned stimulus were unaltered. These findings demonstrate that the mesoamygdaloid dopamine projection modulates the acquisition of a stimulus-reward association, but is apparently without subsequent effect on the rewarding efficacy of a conditioned stimulus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050341
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  • 3
    Electronic Resource
    Electronic Resource
    Cross-sensitisation with d-amphetamine following repeated intra-perifornical sulpiride infusions (1997)
    Springer
    Psychopharmacology 133 (1997), S. 179-187 
    Details
    ISSN: 1432-2072
    Keywords: Key words Perifornical region of the lateral hypothalamus ; Sulpiride ; Sensitisation ; Conditioning ; Mesoaccumbens dopamine projection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Infusions of the dopamine D2/D3 receptor antagonist sulpiride within the perifornical region of the lateral hypothalamus have been reported to increase locomotor activity. The current investigation examined the effect of repeated lateral hypothalamic sulpiride infusions. In experiment 1a, rats were placed repeatedly in an activity chamber either prior to, or following an infusion of 10 μg sulpiride or vehicle. Repeated infusions of sulpiride prior to, but not following exposure to the activity chamber increased locomotor activity during subsequent sessions. In experiment 1b, repeated pretreatment with intra-perifornical sulpiride prior to placement within the activity chamber was found to engender a significant increase in conditioned activity when placed subsequently within the same chamber drug-free. Alternatively, pretreatment with sulpiride in the home cage was found subsequently to engender a significant increase in locomotor activity during a test session with intra-perifornical sulpiride. In experiment 2, repeated pretreatment with intra-perifornical sulpiride significantly increased the locomotor response to a subsequent systemic challenge with d-amphetamine. Animals pretreated in the home cage exhibited a moderate increase in activity over vehicle controls, while animals repeatedly pretreated immediately prior to placement in the activity chamber exhibited the largest response subsequently to d-amphetamine of any group. Experiment 3 showed that repeated sulpiride infusions either 1 mm anterior or 1mm posterior to the perifornical region were without effect upon locomotor activity. These data are suggested to reflect an indirect action of intra-perifornical sulpiride upon the mesoaccumbens dopamine projection, via the level of the ventral tegmental area. Precise neural mechanisms are under current investigation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050389
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  • 4
    Electronic Resource
    Electronic Resource
    Interactions between intra-perifornical region sulpiride and intra-ventral tegmental area AP5 on measures of locomotor activity and conditioned place preference (1998)
    Springer
    Psychopharmacology 136 (1998), S. 105-113 
    Details
    ISSN: 1432-2072
    Keywords: Key words Perifornical region of the lateral hypothalamus ; Ventral tegmental area ; Dopamine ; Activity ; Conditioned place preference ; Sulpiride ; AP5
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Infusions of sulpiride, a dopamine D2/D3 receptor antagonist within the perifornical region of the lateral hypothalamus have been shown previously to exhibit a behavioural profile generally attributed specifically to activation of the mesoaccumbens dopamine projection. Experiment 1 confirmed previous work showing that repeated homecage pretreatment with sulpiride (5 μg) in the perifornical region of the lateral hypothalamus resulted subsequently in an enhanced locomotor response to a d-amphetamine challenge. Experiment 2 examined the possibility that the observed behavioural changes were due to stimulation of the mesoaccumbens dopamine projection via the ventral tegmental area. Thus, repeated intra-perifornical infusions with sulpiride were without effect initially, but resulted in a gradual increase in locomotor activity during subsequent sessions. Intra-ventral tegmental area infusions of the NMDA receptor antagonist AP5 (0.3, 1.0 nmol) were without intrinsic effect upon locomotor activity at any time. However, AP5 blocked the ability of repeated sulpiride infusions to increase locomotor activity, and the ability of intra-perifornical sulpiride to support the acquisition of a conditioned place preference. AP5-sulpiride co-infusions also increased locomotor activity in a non-incremental manner. These data suggest there to be a functionally significant projection from the perifornical region of the lateral hypothalamus to the ventral tegmental area in the control over locomotor activity and rewarded behaviour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050545
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  • 5
    Electronic Resource
    Electronic Resource
    Post-session sulpiride infusions within the perifornical region of the lateral hypothalamus enhance consolidation of associative learning (1998)
    Springer
    Psychopharmacology 140 (1998), S. 354-364 
    Details
    ISSN: 1432-2072
    Keywords: Key words Perifornical region of the lateral hypothalamus ; Amygdala ; Pavlovian conditioning ; Sulpiride ; Dopamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Whilst neurons within the lateral hypothalamus are well known to be responsive to the presentation of previously learned associative stimuli, the consolidation of a Pavlovian association is thought to depend in large part upon other brain regions, including the amygdala. The present study addressed this assumption directly, by examining the effect of post-session infusions of sulpiride within the lateral hypothalamus upon the acquisition of a conditioned approach response in an appetitive differential conditioning task. Subjects were exposed to an initially neutral stimulus (CS+), which immediately preceded the availability of a 10% sucrose reward (US). A second, control stimulus (CS−) was also presented, but never in close temporal proximity to the US. The number and duration of alcove approaches were recorded. Immediately following each training session, subjects were infused bilaterally with sulpiride (0, 0.5, 5 μg) in the vicinity of the perifornical region of the lateral hypothalamus. Sulpiride dose-dependently enhanced the rate of acquisition of a conditioned approach response to presentation of the CS+, but was without affect upon approach behaviour during CS− or US presentations. Thus, 0.5 μg sulpiride facilitated at an early stage (session 2 onwards) the number of alcove approaches to the CS+, while 5 μg sulpiride enhanced to a greater extent the duration of conditioned approach, particularly during later sessions. A subsequent locomotor test using 0.5 mg/kg d-amphetamine indicated that repeated infusions of the higher dose sulpiride (5 μg), but not the lower dose (0.5 μg), resulted in behavioural sensitisation to administration of the psychomotor stimulant. Acquisition of a novel conditioned instrumental response was not affected by previous exposure to sulpiride. These data suggest that dopamine-sensitive neurons within the lateral hypothalamus may play a significant role in the acquisition of appetitive Pavlovian associations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050776
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    Paper (German National Licenses)
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