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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 38 (1980), S. 109-114 
    ISSN: 1432-1106
    Keywords: Neuromuscular ; Reflexes ; Gait
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary If an obstacle impedes the forward swing of a cat's foot, the animal responds by rapidly lifting the foot over the obstacle. In freely moving cats, the electrical activity of hindlimb flexors and extensors was recorded during such reactions elicited both mechanically and electrically. The sequencing of muscle activity was more complex and longer in duration in the mechanically elicited reactions. Anaesthesia of the foot dorsum abolished responses in ankle extensors and knee flexors, and converted the responses of ankle flexors to simple stretch reflexes. Although our findings closely resemble those reported for chronic spinal kittens, there are interesting points of difference, which should be taken into account if the notion of a purely spinal mediation of the placing reaction during stepping is to be accepted.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 37 (1981), S. 490-491 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The binding of3H-spiroperidol to striatal membranes from a strain of mutant Han-Wistar rats was compared with that in normal littermate animals. The specific binding was less in the mutants than the controls. Scatchard analysis revealed that the KD- and Bmax-values for the high affinity binding sites in the mutants are greater than for those in the controls. These findings indicate that the dopamine receptors of the mutants are affected and could explain some of the previous data; it has been suggested that some of the spasticity observed in the mutants may be due to an abnormal functioning of their dopaminergic neurones.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2013
    Keywords: muscle spindles ; fusimotoneurons ; substantia nigra ; picrotoxin ; muscimol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Picrotoxin and muscimol were unilaterally injected into the postero-lateral part of the reticular zone of substantia nigra (p1SNR) through chronically implanted guide cannulae in ketamine-anasthetized cats. Afferent activity of pretibial flexor muscle spindle primary and secondary endings was recorded before and after drug administration, and spindle sensitivity monitored during both sinusoidal and ramp stretch of the receptor-bearing muscle. From changes in spindle sensitivity after drug injection it is deduced that unilateral block by picrotoxin of the action of GABA on postsynaptic receptors in plSNR removes tonic static fusimotor action from flexor muscle spindle primary endings. Secondary endings seemed largely unaffected. The effect on primary endings is reversed by a subsequent injection of muscimol. It is concluded that the central nervous system, through GABA-modulated nigral output neurons, can control static fusimotor action onto flexor muscle spindle primary and secondary endings separately to some extent.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 317 (1981), S. 54-60 
    ISSN: 1432-1912
    Keywords: Substantia nigra ; GABA receptors ; Stereotypy ; Rotational behaviour ; Motor disturbances
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The behaviour of cats after unilateral injections of muscimol, picrotoxin and bicuculline into the posterior and lateral parts of the substantia nigra was observed. The antagonism between muscimol and picrotoxin was limited to some effects of the drugs: (1) muscimol-induced sniffing, licking and enhanced locomotor activity was attenuated by picrotoxin in contrast to the muscimol-induced contralateral turning which was even enhanced by picrotoxin; (2) picrotoxin-induced balance disorders as well as characteristic motor disturbances in the hind legs remained unaffected following an additional treatment with muscimol. Furthermore, subcutaneously given apomorphine did not affect the picrotoxin-induced balance and hind leg disorders, although the apomorphine-induced stereotyped behaviour itself was enhanced and suppressed by intranigral administration of muscimol and picrotoxin respectively. The conclusion is reached that there are at least two distinct populations of GABA receptors within the substantia nigra: one group controlling or being controlled by dopaminergic neurons and one group operating fully independently of the former neurons. The similarities to experiments on rats are stressed. The mechanism underlying the muscimol-resistant picrotoxin-induced effects (balance disorders and motor disturbance of the hind legs) is discussed.
    Type of Medium: Electronic Resource
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