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  • 1
    ISSN: 1432-1106
    Keywords: Pedunculopontine nucleus ; Substantia nigra pars compacta ; Excitatory responses ; Glutamate ; Acetylcholine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The nature of the synaptic transmitter involved in the excitatory fibers linking the nucleus tegmenti pedunculopontinus (PPN) to the pars compacta of the substantia nigra (SNPC) was investigated using microiontophoretic techniques in rats anesthetized with ketamine. Among the SNPC cells activated orthodromically by PPN electrical stimulation, only a few cells were weakly excited by iontophoretically administered acetylcholine (Ach) while most were not affected. Conversely all cells were promptly and powerfully excited by short pulses of glutamate (GLU). The administration of the GLU antagonists glutamic acid diethylester (GDEE) and D-α-aminoadipic acid (DAA) reversibly and simultaneously suppressed both the PPN-evoked orthodromic response and the GLU-induced excitation of SNPC cells without affecting their response to iontophoretic Ach. GDEE was more effective than DAA in counteracting the synaptically evoked excitation. On the other hand, atropine, while antagonizing the Ach response in those cells which were cholinoceptive, did not affect either the PPN-evoked or the GLU-induced excitation. Hence, despite the presence of cholinergic cells in the PPN region, Ach does not appear to be involved in the excitatory PPNSNPC pathway. The present findings suggest that the excitatory PPN fibers innervating the SNPC may utilize GLU or a closely related amino acid as a neurotransmitter.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1106
    Keywords: Kainic acid ; Striatum ; Substantia nigra ; Aminoacids iontophoresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Kainic acid (KA 1.2–1.5 μg) was injected unilaterally into the rat striatum (ST). Fifteen to 30 days later neurons of the substantia nigra (SN) were identified by antidromic stimulation from the ST or medial forebrain bundle (MFB). The projecting axons had conduction velocity similar to that recorded in unlesioned animals. Responses to iontophoretically applied dopamine (DA), glutamate (GLU), and GABA (5–100 nA) were recorded from neurons of the dopaminergic pars compacta-striatal projection. Control experiments were performed in intact rats. GABA and DA inhibited neurons tested in controls while GLU had an excitatory effect. Changes in firing rate induced by GABA and GLU developed 1–5 s after the beginning of their ejection while the action of DA appeared after a delay of 20–40 s. Neurons in lesioned animals showed a net decrease in sensitivity to all three neurotransmitters. The highest current tested gave responses 50–70% lower than in controls. The data suggest that destruction of striatal efferents with KA does not induce hypersensitivity in the pars compacta of the SN.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Bulletin of Mathematical Biology 43 (1981), S. 81-88 
    ISSN: 0092-8240
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Mathematics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Bulletin of Mathematical Biology 43 (1981), S. 81-88 
    ISSN: 0092-8240
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Mathematics
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1435-1463
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Bromocriptine reduces the spontaneous firing rate of neurons in the pars compacta of the substantia nigra but does not change the electrical activity of the neurons located in the pars reticulata. On the other hand, bromocriptine induces contralateral circling behaviour in rats with unilateral 6-hydroxydopamine nigral lesion. This increased motor activity follows an initial period of hypomotility. The decrease of the neuronal firing rate in the pars compacta of the substantia nigra coincides with the hypomotility observed in the lesioned rats.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of mathematical biology 43 (1981), S. 81-88 
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A correlation matrix analysis is applied to the base sequence of MS2 and ϕX174 in comparison with sets of simulated sequences with different degrees of constaint Significant differences between a codified sequence, and a statistical one in terms of the “correlation matrix” for sets of different length cannot be found. This result is analysed in terms of nucleotide sequences with different levels of informational content.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1439-6327
    Keywords: Key words Aerobic dance ; Blood lactate ; Heart rate ; Oxygen uptake ; Oxygen pulse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of this research was to investigate the physiological responses and, in particular, the participation of lactic acid anaerobic metabolism in aerobic dance, which is claimed to be pure aerobic exercise. In contrast to previous studies, that have put subjects in very unfamiliar situations, the parameters were monitored in the familiar context of gymnasium, practice routine and habitual instructor. A group of 30 skilled fairly well-trained women performed their usual routine,␣a combination of the two styles: low (LI) and high impact (HI), and were continuously monitored for heart rate (HR) and every 8 min for blood lactate concentration ([La−]b). Of the group, 15 were tested to determine their maximal aerobic power (V˙O2max) using a cycleergometer. They were also monitored during the routine for oxygen uptake (V˙O2) by a light telemetric apparatus. The oxygen pulses of the routine and of the corresponding exercise intensity in the incremental test were not statistically different. The mean values in the exercise session were: peak HR 92.8 (SD 7.8)% of the subject's maximal theoretical value, peak V˙O2 99.5 (SD 12.4)% of V˙O2max, maximal [La−]b 6.1 (SD 1.7) mmol · l−l, and mean 4.8 (SD 1.3) mmol · l−l. Repeated measures ANOVA found statistically significant differences between the increasing [La−]b values (P 〈 0.001). In particular, the difference between the [La−]b values at the end of the mainly LI phase and those of the LI-HI combination phase, and the difference between the samples during the combination LI-HI phase were both statistically significant (both P= 0.002 and P= 0.002). The similar oxygen pulses confirmed the validity of the present experiment design and the reliability of HR monitoring in this activity. The HR, V˙O2 and, above all, the increase of [La−]b to quite high values, showing a non steady state, demonstrated the high metabolic demand made by this activity that involved lactic acid metabolism at a much higher level than expected.
    Type of Medium: Electronic Resource
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