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  • 1
    ISSN: 1435-1463
    Keywords: Keywords: MPTP ; motor activity ; L-Dopa ; subthreshold dose ; suprathreshold dose ; lamotrigine ; FCE 26743 ; L-Deprenyl ; phenytoin ; co-administration ; synergism ; restoration ; dopamine ; parkinsonism ; anticonvulsive agents ; C57 BL/6 mice.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary. The effects of co-administration of the dopamine precursor, L-Dopa, with anticonvulsant and putative anticonvulsive agents upon the motor activity of hypoactive MPTP-treated C57 BL/6 mice were measured in six experiments. In each case, MPTP (2 × 40 mg/kg, s.c., separated by a 24-hr interval) was administered four to six weeks prior to behavioural testing. Thus, the effects of these agents combined with either a single acute, subthreshold dose (5 mg/kg, s.c.) of L-Dopa, or, with chronically-administered, suprathreshold doses (20 mg/kg, s.c.) of L-Dopa were studied. In the former, lamotrigine, FCE 26743 and L-Deprenyl, injected 60 min before subthreshold L-Dopa (5 mg/kg), each induced an antiparkinsonian action in MPTP-treated mice that consisted of dose-specific, as opposed to dose-related, elevations of locomotion and rearing behaviour. In the latter, lamotrigine (all three measures of activity at 3 mg/kg), FCE 26743 (locomotion and total activity at 3; rearing at 1 and 3 mg/kg) and L-Deprenyl (locomotion and total activity at 1 and 3 mg/kg), but not phenytoin (neither at 1 nor 3 mg/kg), reinstated the motor activity-stimulating effects of the threshold dose of L-Dopa (20 mg/kg) in L-Dopa-tolerant, MPTP-treated mice. Neurochemical analyses confirmed severe DA depletions in MPTP-treated mice. Since neither lamotrigine, FCE 26743 nor L-Deprenyl, nor subthreshold L-Dopa, by themselves increased the motor behaviour of MPTP-treated mice, a synergistic effect of the co-administration is concluded. Further, since the suprathreshold dose of L-Dopa by itself failed to stimulate motor activity in the MPTP mice following chronic (25 daily injections) administrations of the compound, it is suggested that a restorative effect, in combination with lamotrigine, FCE 26743 or L-Deprenyl was evidenced. The potential therapeutic benefits of anticonvulsant or putative anticonvulsive compounds for parkinsonian symptoms are discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neural transmission 106 (1999), S. 283-300 
    ISSN: 1435-1463
    Keywords: Keywords: C57 Bl/6 mice ; MPTP ; suprathreshold ; L-Dopa ; 20 mg/kg ; chronic injections ; tolerance ; NMDA antagonists ; MK-801 ; CGP 40116 ; reinstatement ; synergism ; parkinsonism.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary. Three experiments were performed to study the development and manipulation of tolerance to a suprathreshold dose of L-Dopa (20 mg/kg, s.c.) in MPTP-treated and control (saline-injected) C57 Bl/6 mice. The motor activity reinstatement effect of this dose of L-Dopa upon MPTP-treated mouse behaviour deteriorated from the 13th injection (Test Day 8) of L-Dopa onwards and reached basal level (i.e. no stimulatory effects of the drug) by the 16th administration (Test Day 10). Administration of L-Dopa to control mice reduced locomotor and rearing activity throughout the tolerance development period (Test Days 1–12) during the first hour after injection, and then increased locomotor activity during the second hour. The effects of combining either a noncompetitive, MK-801, or a competitive, CGP 40116, glutamate antagonist with L-Dopa, following tolerance development, were assessed in MPTP mice on the 23rd day of L-Dopa administration (Test Day 13). MK-801 (0.1 mg/kg, s.c.) reinstated the locomotory and rearing behaviour induced by L-Dopa; CGP 40116 did so also to a greater extent in the dose range 0.01 to 0.03 mg/kg. These results indicate that MPTP-treated mice continue to offer a useful parkinsonian model also for the examination of different aspects of the "wearing-off" phenomenon of L-Dopa tolerance and in particular the putative glutamatergic involvement. The clinical consequences may be far-reaching for the utility of L-Dopa in Parkinson's disease, whether the effects demonstrated be of a reinstatement or synergistic na-ture, once therapeutically adequate glutamate antagonists are more readily available.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neural transmission 97 (1994), S. 197-209 
    ISSN: 1435-1463
    Keywords: Motor behaviour ; L-Dopa ; MK-801 ; CGP40116
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Four experiments were performed to investigate whether or not co-administration of NMDA-antagonists potentiate the effect of an ineffective dose of L-Dopa on motor activity in hypoactive MPTP-treated mice. Motor activity was measured in an automated system recording both locomotion (horizontal) and rearing (vertical) activity. L-Dopa alone, at doses of 10 and 20 mg/kg, but not 5 mg/kg, expressed an anti-akinesia effect in MPTP-treated mice. The non-competitive NMDA-antagonist MK-801 (0.03, 0.1, and 0.3mg/kg) increased by itself both locomotion (0.1 and 0.3 mg/kg) and rearing (0.03 mg/kg) in control (saline-treated) mice whereas no effect was seen in the MPTP-treated mice. Combined with 5 mg/kg L-Dopa, MK-801 (0.1 mg/kg) increased locomotion in MPTP-treated mice. There was no interaction seen between L-Dopa and MK 801 in the control mice. CGP40116 and CGP40117, the active D- and the inactive L-stereoisomer of the competitive NMDA-inhibitor CGP 37849, respectively, were also administered together with 5 mg/kg L-Dopa. Both doses (0.003 and 0.03 mg/kg) of CGP 40116 in contrast to CGP 40117, produced anti-akinesia effect in MPTP-treated mice. CGP 40116 (0.0001 to 0.1 mg/kg) together with 5 mg/kg L-Dopa did not affect behaviour in control mice but produced (0.01 mg/kg CGP 40116 and 5 mg/kg L-Dopa) in the MPTP-treated mice an anti-akinesia effect. Our findings indicate that the non-competitive NMDA-antagonist MK-801, at doses with reported side-effects, only increase locomotion while rearing remained unaltered in MPTP-treated mice when combined with 5 mg/kg L-Dopa. Only the active stereoisomer CGP 40116 in contrast to CGP 40117, at doses far below reported side-effects, dose-dependently modulated the anti-akinesia effect of a subthreshold dose of L-Dopa. Such data thus support the notion that this behavioural modulation was regulated via NMDA-receptors. The synergism between L-Dopa and the competitive NMDA-antagonist CGP40116 has a potential in treatment of Parkinson's disease to reduce the side-effects of doses of L-Dopa that are used today.
    Type of Medium: Electronic Resource
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