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  • 1
    ISSN: 1432-1106
    Keywords: Key words Human gait ; Transcranial magnetic stimulation ; Motor cortex ; Leg flexor/extensor muscle ; Corticospinal input ; Visual control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The aim of this study was to investigate visuomotor control during human gait. It was assumed that visual input should modulate transcranially evoked motor potentials (EMPs) during walking. The effect of transcranial magnetic stimulation (TMS) in a visually guided precision stepping task was compared with that during normal gait. EMPs were studied in tibialis anterior (TA), gastrocnemius (GM), and abductor digiti minimi (AD) muscles during treadmill walking. In both stepping tasks, a facilitation of EMPs was observed prior to activation of the respective leg muscle. EMP facilitation proved to be modulated throughout the stride cycle when normalising EMP with respect to the underlying electromyogram (EMG). Facilitation was strongest in TA prior to the swing phase. Significant differences of EMP facilitation between the visual and control tasks were present. In the visual task, maximal facilitation of TA EMPs prior to and during the swing phase was decreased compared to the control task. Conversely, there was increased facilitation of GM EMPs during swing phase of the visual task, prior to the heel strike and prior to the plantarflexion, which was the moment when the target was hit. Thus, the effect of visual input upon EMPs in TA and GM was differential and reciprocal according to the respective functional state. The results support the hypothesis of a conditioning effect of visual or, alternatively volitional, drive on EMPs during stepping.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2072
    Keywords: Key words Ethanol ; 5-HT ; Rats ; Drug discrimination ; Alcohol ; TFMPP ; mCPP ; RU 24969 ; CGS 12066B ; 8-OH DPAT
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  A drug discrimination procedure was used to characterize the ethanol-like effects of a variety of 5-HT1 agonists. Previous studies found that the degree of substitution of the 5-HT1B/2C agonist TFMPP (m-trifluoromethylphenylpiperazine) depended on the training dose of ethanol. The present studies extend this initial finding to four additional 5-HT agonists with different selectivity for 5-HT1A, 5-HT1B, or 5-HT2C receptors: CGS 12066B (7-trifluoromethyl-4(4-methyl-1-piperazinyl)-pyrrolo[1,2-a]quinoxaline maleate), mCPP [1-(3-chlorophenyl)piperazine diHCl], RU 24969 [5-methoxy-3(1,2,3,4-tetrahydro-4-pyridinyl]-1H-indole succinate and 8-OH DPAT [(±)-8-hydroxy-2-(di-n-propylamino)tetralin HBr]. Separate groups of rats were trained to discriminate 1.0 g/kg (n=7), 1.5 g/kg (n=6) or 2.0 g/kg (n=8) ethanol from water. Following training, three to five doses of each 5-HT agonist were tested twice in each rat. The most selective 5-HT1B agonist tested, CGS 12066B (3–17 mg/kg; IP), completely substituted for the 1.0 g/kg ethanol, but not for 1.5 or 2.0 g/kg ethanol. Likewise, the 5-HT1B/2C agonist mCPP (0.56–1.7 mg/kg; IP) completely substituted only in the 1.0 g/kg ethanol training group. The 5-HT1A/1B agonist RU 24969 (0.1–3.0 mg/kg; IP) substituted for all training doses of ethanol, although in a lower proportion of the rats tested in the 2.0 g/kg ethanol training group. Finally, the 5-HT1A agonist 8-OH DPAT (0.1–1.0 mg/kg; IP) did not substitute completely for any ethanol training dose. The results consistently show that agonists with 5-HT1B activity produce discriminative stimulus effects similar to low and intermediate, but not high, ethanol training doses.
    Type of Medium: Electronic Resource
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