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  • Articles: DFG German National Licenses  (7)
  • NMDA receptor  (4)
  • Dopamine  (3)
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  • Articles: DFG German National Licenses  (7)
Material
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neural transmission 78 (1989), S. 29-41 
    ISSN: 1435-1463
    Keywords: Learning and memory ; interference ; striatum ; glutamate ; NMDA receptor ; AP-5 ; rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Prefrontal cortex and neostriatum constituting the prefrontal system are connected by glutamatergic neurones. The involvement of this corticostriatal projection in control of maze performance of rats was investigated. Glutamatergic transmission mediated by N-methyl-D-aspartate (NMDA) receptors was blocked by intrastriatal injections of dl-2-amino-5-phosphonovaleric acid (AP-5) (50 nmole in 0.5 Μl). In experiment 1, intrastriatal AP-5 was found to increase the number of errors during acquisition of a delayed alternation task in a T-maze. In experiment 2, the effect of intrastriatal AP-5 on acquisition of different 8 arm maze tasks was investigated. AP-5 did not affect the number of reentries on spontaneous and reinforced alternation; pre- and postdelay errors on delayed alternation were not altered. Therefore, intrastriatal NMDA receptor blockade impairs acquisition of a delayed alternation in a T-maze, while intrastriatal blockade of NMDA receptors does not affect acquisition of different 8 arm maze tasks. The impairment in the T-maze task appears not to be due to deficient acquisition of spatial information per se, since 8 arm maze performance is intact. Instead, repeated delays in the T-maze task seem to be the critical component that gives difficulties in acquisition. These difficulties in bridging successive temporal discontiguities were attributed to an increased susceptibility to external and internal interfering stimuli during delays. Thus, striatal NMDA receptors within the prefrontal system may be involved in correct response retention over the duration of delays.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1435-1463
    Keywords: NMDA receptor ; locomotion ; catalepsy ; stereotypy ; rat ; CGP 37849 ; dizocilpine (MK-801) ; glycine ; D-cycloserine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of competitive (CGP 37849 and CGP 39551) and noncompetitive (dizocilpine) N-methyl-D-aspartate (NMDA) antagonists were tested in three animal models (catalepsy, sniffing, locomotion) and, in addition, the modulation of these effects by an agonist of the strychnine-insensitive glycine binding site was investigated. Both competitive and non-competitive NMDA antagonists reduced neuroleptic-induced catalepsy. Weak sniffing was induced by the competitive antagonist but strong sniffing by the non-competitive NMDA antagonist. Due to muscle relaxation the competitive antagonist reduced locomotion, in contrast to stimulation of locomotor activity induced by the noncompetitive NMDA antagonist. The glycine agonist (D-cycloserine) potentiated the effects of the non-competitive but antagonized those of the competitive NMDA antagonist.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 99 (1994), S. 524-528 
    ISSN: 1432-1106
    Keywords: Prefrontal cortex ; 6-Hydroxydopamine ; Dopamine ; Noradrenaline ; Reaction and movement times ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We examined the effects of bilateral 6-hydroxydopamine (6-OHDA) lesions of the medial prefrontal cortex (PFC) in rats on motor initiation and execution in a simple reaction time task. Reaction times (RT) and movement times (MT) were measured in trained rats on four preand postoperative days. Animals with 6-OHDA lesions were selectively impaired on motor initiation as measured by a significant increase in RT on each postoperative day. Motor execution was intact postoperatively, since MT was not altered. Neurochemical analysis revealed a significant depletion of prefrontal dopamine (DA) and noradrenaline (NA) in lesioned animals. It was concluded that DA and, to a lesser extent, NA in the rat PFC were involved in monitoring RT performance.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2072
    Keywords: Glutamate ; Dopamine ; Stereotyped sniffing ; AP-5 ; Haloperidol ; Clozapine ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract dl-2-amino-5-phosphonovaleric acid (AP-5), which blocks glutamatergic transmission at the NMDA-preferring receptor, was injected into the antero-dorsal striatum of rats. AP-5-induced behavioural changes were assessed i) using a stereotypy rating scale and ii) using an experimental chamber designed to quantify sniffing. In both behavioural situations it was shown that AP-5 (10 μg/0.5 μl) induced continuous intensive sniffing similar to that induced by small doses of systemically administered amphetamine or apomorphine. However, oral stereotypies were not induced by AP-5. Systemically injected clozapine (5 and 10 mg/kg SC) as well as haloperidol (0.1 mg/kg IP) antagonized AP-5-induced sniffing. These results show that besides dopamine receptors, NMDA receptors are involved in the control of sniffing. In behavioural terms, the effect of glutamate mediated by the NMDA receptor in the striatum is opposite to that of dopamine.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 95 (1988), S. 271-275 
    ISSN: 1432-2072
    Keywords: Dopamine ; Maternal behaviour ; Response-switching ; Apomorphine ; Haloperidol ; House mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Maternal pup searching behaviour of lactating house mice treated with apomorphine, haloperidol or saline was examined on a running board with a central depression as a nest. Pup searching was elicited by artificial ultrasonic stimuli: a female moved out from the nest either towards a 50 kHz tone (key stimulus) which is adequate to activate species specific pup searching behaviour or towards a 20 kHz tone (neutral stimulus), thus showing her preference for one of these stimuli. Under apomorphine (0.00625; 0.0125; 0.025 mg/kg) the females preferred the key stimulus. Nevertheless apomorphine (0.00625–0.025 mg/kg) prolonged response latencies and shortened the duration of pup searching. At the highest dose (0.05 mg/kg), apomorphine induced stereotyped sniffing. Haloperidol (0.025; 0.05; 0.1 mg/kg) had opposite effects to apomorphine: it lowered the threshold for elicitation, shortened response latencies and prolonged the duration of pup searching. Females treated with haloperidol (0.025–0.1 mg/kg) did not prefer the key stimulus. Changes in response elicitation and in the performance of pup searching induced by apomorphine and haloperidol, respectively, were assumed to be due to i) a reduced and an increased responsiveness to external stimuli respectively, ii) an enhanced and a reduced tendency for response switching respectively, and iii) a preference for spontaneous behaviour in apomorphine-treated females, with an increased dependence on exteroceptive stimuli following haloperidol.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Amino acids 14 (1998), S. 5-10 
    ISSN: 1438-2199
    Keywords: Basal ganglia loops ; Reward ; Sensitization ; NMDA receptor ; Parkinson's disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In an attempt to formulate a working hypothesis of basal-ganglia functions, arguments are considered suggesting that the basal ganglia are involved in a process of response selection i.e. in the facilitation of “wanted” and in the suppression of “unwanted” behaviour. The meso-accumbal dopamine-system is considered to mediate natural and drug-induced reward and sensitization. The meso-striatal dopamine-system seems to fulfill similar funcions: It may mediate reinforcement which strengthens a given behaviour when elicited subsequently, but which is not experienced as reward or hedonia. Glutamate as the transmitter of the corticofugal projections to the basal ganglia nuclei and of the subthalamic neurons is critically involved in basal ganglia funcions and dysfunctions; for example Parkinson's disease can be considered to be a secondary hyperglutamatergic disease. Additionally, glutamate is an essential factor in the plasticity response of the basal-ganglia. However, opposite to previous suggestions, the NMDA-receptor blocker MK-801 does not prevent psychostimulant- nor morphine-induced day to day increase (sensitization) of locomotion. Also the day to day increase of haloperidol-induced catalepsy was not prevented by MK-801.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 151 (2000), S. 142-151 
    ISSN: 1432-2072
    Keywords: Keywords Sensitization ; MK-801 ; Dizocilpine ; State dependency ; Drug discrimination ; Conditioning ; Learning ; Behavioral plasticity ; NMDA receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Rationale: It is widely assumed that various forms of neural and behavioral plasticity, including sensitization, are strongly dependent on the activation of N-methyl-d-aspartate (NMDA)-receptors, but evidence also exists to suggest that not all forms of sensitization are unequivocally blocked by NMDA-receptor antagonism. Also, findings from studies examining the effects of NMDA-receptor blockade on forms of behavioral plasticity other than locomotor sensitization (various forms of tolerance, sensitization of catalepsy, and learning and conditioning) reinforce the view that forms of behavioral plasticity exist that are not blocked by NMDA-receptor antagonists. Objectives: Since the publication of two reviews addressing this issue in detail, this field of research has continued to be very active and controversial, and a number of further studies have been published in the meantime which are relevant to the topic. The aim of this review is to provide a summary of this literature and to consider new approaches that might make important contributions to the present discussion. Results and conclusions: The studies reviewed herein have produced results both consistent with and in contradiction to the view that MK-801 and related drugs block behavioral plasticity, and the debate about how exactly MK-801 and related drugs interact with other drugs in sensitization experiments is still in full swing. What seems crucial for future studies relating to this subject is a careful experimental design to reduce the number of potential interpretations of the findings.
    Type of Medium: Electronic Resource
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