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  • 1
    Electronic Resource
    Electronic Resource
    A microiontophoretic study on the nature of the putative synaptic neurotransmitter involved in the pedunculopontine-substantia nigra pars compacta excitatory pathway of the rat (1986)
    Springer
    Experimental brain research 62 (1986), S. 470-478 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00236025
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  • 2
    Electronic Resource
    Electronic Resource
    The catecholamine uptake blocker nomifensine protects against MPTP-induced parkinsonism in monkeys (1986)
    Springer
    Experimental brain research 63 (1986), S. 216-220 
    Details
    ISSN: 1432-1106
    Keywords: MPTP ; Parkinsonism ; Dopamine ; Nomifensine ; Degeneration prevention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Administration of MPTP (1-methyl-1,2,3,6-tetrahydropyridine) to Macaca fascicularis monkeys produced severe parkinsonism (hypokinesia, tremor, rigidity, aphagia, adipsia) and more than 90% loss of nigral dopamine neurons, striatal dopamine content and striatal 3H-mazindol binding. Treatment with the catecholamine uptake blocker nomifensine counteracted the behavioral, histological and neurochemical effects induced by MPTP. For obtaining best protection, nomifensine had to be administered for weeks after MPTP. The results suggest that the selective target-directed neurotoxic action of MPTP on dopamine neurons in monkeys is mediated via the dopamine uptake mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235666
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  • 3
    Electronic Resource
    Electronic Resource
    Neuronal responses to iontophoretically applied dopamine, glutamate, and GABA of identified dopaminergic cells in the rat substantia nigra after kainic acid-induced destruction of the striatum (1982)
    Springer
    Experimental brain research 46 (1982), S. 377-382 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00238632
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  • 4
    Electronic Resource
    Electronic Resource
    Dopaminergic and non-dopaminergic neurons in substantia nigra: Differential response to bromocriptine (1980)
    Springer
    Journal of neural transmission 48 (1980), S. 297-303 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF01250664
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  • 5
    Electronic Resource
    Electronic Resource
    Evidence that non-NMDA receptors are involved in the excitatory pathway from the pedunculopontine region to nigrostriatal dopaminergic neurons (1992)
    Springer
    Experimental brain research 89 (1992), S. 79-86 
    Details
    ISSN: 1432-1106
    Keywords: Basal ganglia ; Pedunculopontine nucleus ; Substantia nigra pars compacta ; Excitatory amino acids ; Acetylcholine ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Extracellular single-neuron recordings were obtained from electrophysiologically identified nigrostriatal neurons in chloral hydrate anesthetized rats, in order to test the hypothesis that excitatory amino acid receptors are involved in responses of these neurons to electrical stimulation of the pontine region where the pedunculopontine nucleus (PPN) is located. The effects of iontophoretic application of excitatory amino acids and their antagonists as well as of cholinergic antagonists were tested on the fast orthodromic excitation of nigrostriatal neurons evoked by stimulation of the PPN region. The N-methyl-D-aspartate (NMDA) receptor antagonist D-a-aminoadipic acid as well as the cholinergic receptor antagonists mecamylamine and atropine failed to suppress the synaptic excitation of nigral neurons. The NMDA receptor antagonist DL-2-amino-5-phosphonovalerate exerted a weak depressant action on the synaptic response in a few neurons only. On the contrary, the broad spectrum antagonists of excitatory amino acid receptors kynurenic acid and gamma-Dglutamyl-amino-methyl-sulphonate were found to block simultaneously both the synaptic excitation and the neuronal responses to iontophoretic pulses of glutamate while leaving unaffected the neuronal responses to local application of acetylcholine or carbachol. The competitive antagonist of non-NMDA receptors 6-cyano-2,3-dihy-droxy-7-nitro-quinoxaline suppressed the synaptic excitation at ejection currents which antagonized neuronal responses to quisqualate and kainate. These results suggest that PPN excitatory fibers synapsing onto pars compacta nigrostriatal neurons utilize an excitatory amino acid as a synaptic transmitter acting preferentially on non-NMDA receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229003
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  • 6
    Electronic Resource
    Electronic Resource
    Responses to reward in monkey dorsal and ventral striatum (1991)
    Springer
    Experimental brain research 85 (1991), S. 491-500 
    Details
    ISSN: 1432-1106
    Keywords: Basal ganglia ; Caudate ; Putamen ; Accumbens ; Behavior ; Drinking ; Motivation ; Stimulusreward association ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The sources of input and the behavioral effects of lesions and drug administration suggest that the striatum participates in motivational processes. We investigated the activity of single striatal neurons of monkeys in response to reward delivered for performing in a go-nogo task. A drop of liquid was given each time the animal correctly executed or withheld an arm movement in reaction to a visual stimulus. Of 1593 neurons, 115 showed increased activity in response to delivery of liquid reward in both go and nogo trials. Responding neurons were predominantly located in dorsal and ventromedial parts of anterior putamen, in dorsal and ventral caudate, and in nucleus accumbens. They were twice as frequent in ventral as compared to dorsal striatal areas. Responses occurred at a median latency of 337 ms and lasted for 525 ms, with insignificant differences between dorsal and ventral striatum. Reward responses differed from activity recorded in the face area of posterior putamen which varied synchronously with individual mouth movements. Responses were directly related to delivery of primary liquid reward and not to auditory stimuli associated with it. Most of them also occurred when reward was delivered outside of the task. These results demonstrate that neurons of dorsal and particularly ventral striatum are involved in processing information concerning the attribution of primary reward.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231732
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  • 7
    Electronic Resource
    Electronic Resource
    Tonically discharging neurons of monkey striatum respond to preparatory and rewarding stimuli (1991)
    Springer
    Experimental brain research 84 (1991), S. 672-675 
    Details
    ISSN: 1432-1106
    Keywords: Caudate ; Putamen ; Tonic ; Behavior ; Context ; Set ; Stimulus-stimulus association ; Visual ; Auditory ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The behavioral relationships of 396 striatum neurons with regular, tonically elevated discharge rates were studied. While monkeys performed a delayed gonogo task, neurons predominantly located in medial putamen responded with phasic depressions (n = 30) or activations (n = 5) to task-specific stimuli. Particularly effective was an instruction light preparing for movement or no-movement reactions, and an auditory signal associated with reward delivery. Stimuli triggering arm or mouth movements were less effective. The data demonstrate that these usually poorly modulated neurons display context-dependent phasic activity in specific behavioral situations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230981
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  • 8
    Electronic Resource
    Electronic Resource
    Saccadic reaction times, eye-arm coordination and spontaneous eye movements in normal and MPTP- treated monkeys (1989)
    Springer
    Experimental brain research 78 (1989), S. 253-267 
    Details
    ISSN: 1432-1106
    Keywords: MPTP ; Dopamine ; Eye movements ; Eye-arm coordination ; Reaction times ; Parkinsonism ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The oculomotor performance of monkeys was investigated before and after destruction of nigrostriatal dopamine neurons by MPTP (1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine). Stimulus-triggered saccades and their relationships to arm movements were measured in a reaction time task. Spontaneous eye movements were recorded while monkeys sat in a primate chair and looked around the laboratory without performing any task. In the reaction time task, saccades and arm movements were commonly triggered by the rapid, visible and audible opening of a small food-containing box which was located at a constant position in front of the animal at eye level. Median saccadic latencies ranged from 68 to 118 ms in intact animals. Saccades were followed by onset of electromyographic (EMG) activity in the extensor digitorum communis and the biceps brachii, the prime mover muscles for the following arm reaching movement. Latencies of stimulus-triggered saccades showed an absence of linear relationship to EMG or arm movement reaction time in intact animals (correlation coefficients of 0.15–0.56). This suggests that eye and arm movements were initiated independently from each other in this experimental situation. Treatment with MPTP resulted in 98–99.5% loss of striatal dopamine in both monkeys. This induced a 29–93% increase in saccadic latency in the reaction time task. The sequential occurrence of saccade, EMG activity and arm movement in each trial was preserved, although intervals between onset of saccades and onsets of EMGs and arm movements were prolonged by 53–173% and 33–679% respectively. Onsets of individual saccades remained uncorrelated with onsets of EMG activity or arm movement. Spontaneous eye movements were strongly reduced in frequency and amplitude after MPTP. Administration of the dopamine precursor L-Dopa increased spontaneous eye movements for less than two hours. The severe deficits in stimulus-triggered and spontaneous saccadic eye movements are oculomotor components of hypokinesia arising after MPTP-induced lesions of the nigrostriatal dopamine system in primates. The data are further evidence for a role of midbrain dopamine neurons in behavioral responsiveness and spontaneous activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228897
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  • 9
    Electronic Resource
    Electronic Resource
    Behavioural and electrocortical modifications induced in the rat by intraventricular injection of physalaemin and eledoisin (1974)
    Springer
    Psychopharmacology 38 (1974), S. 211-218 
    Details
    ISSN: 1432-2072
    Keywords: Peptides ; Physalaemin ; Eledoisin ; Substance P ; EEG ; Behaviour ; Intraventricular Injection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of intraventricular injection of eledoisin and physalaemin in the rat were studied. Both peptides reduced explorative behaviour; eledoisin, but not physalaemin, produced catatonia, reduction of muscular strength, tremor and sialorrhea. The electrocorticogram showed the signs of a depressive effect both after physalaemin and eledoisin administration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00421373
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