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Automatic postural responses in the cat: Responses to headward and tailward translation (1983)

Rushmer, D. S. ; Russell, C. J. ; Macpherson, J. ; [et al.]

Springer

Experimental brain research 50 (1983), S. 45-61

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ISSN: 1432-1106

Keywords: Postural reflexes ; Unexpected postural perturbations ; Electromyographic activity ; Hind limb and forelimb muscles ; Cat

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine

Notes: Summary EMG responses, vertical and A-P shear forces and kinematics of “automatic postural responses” to unexpected translational perturbations in the headward and tailward directions were studied in cats. Muscles acting on the major joints of the forelimbs and hindlimbs were studied. Movement of the animals in response to perturbation were highly stereotyped and consisted of two phases: (1) motion of the feet during platform movement while the trunk remained relatively stationary followed by (2) active correction of posture by movement of the trunk in the direction of perturbation. Vertical force changes occurred after the perturbation was well underway (latency 65 ms) and were related to the displacement of the center of mass and active correction of trunk position. Shear forces showed both passive (inertial) and active components and suggested that the majority of the torque necessary for po,stural correction was generated by the hindlimb. EMG responses in forelimb and shoulder muscles were most correlated with increase in vertical force, showing a generalized co-contraction in tailward translation (when these limbs were loaded) and little activity when the forelimbs were unloaded. EMG responses in hindlimb showed reciprocal activation of agonists and antagonists during perturbation with strong synergies of thigh and foot flexors in tailward translation and thigh and foot extensors in headward translation. The forelimb EMG patterns were most consistent with the conclusion that the forelimb is used primarily for vertical support during perturbation. It was concluded that hindlimb EMG responses were appropriate for both vertical support and performance of the postural correction. The hindlimb muscle synergies observed during translation are the “mirror image” of those observed in humans by other workers.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00238231

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The action of iontophoretically applied L-glutamate on an insect visceral muscle (1983)

Dunbar, Stuart J. ; Piek, Tom

New York, NY [u.a.] : Wiley-Blackwell

Archives of Insect Biochemistry and Physiology 1 (1983), S. 93-103

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ISSN: 0739-4462

Keywords: glutamate ; insect ; δ-philanthotoxin ; iontophoresis ; visceral muscle ; Locusta migratoria ; proctolin ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology

Notes: 1) lontophoretic application of L-glutamate was employed to study the distribution of glutamate receptors in the superior longitudinal (SL) muscles of the locust (Locusta migratoria) hindgut, in which spontaneous activity was inhibited using normal saline containing 5 mM MgCl2. 2) Junctional glutamate potentials with a rise time of 50-100 ms (peak) and a decay time of 250-400 ms were recorded at localized sites using ejection pulses in the range 5-10 nC. Most active sites were found in interfiber clefts and were spaced at about 250-300 μm intervals. 3) Desensitization of glutamate receptors occurred using ejection frequencies 〉 0.2 Hz. Desensitization could be irreversibly blocked using the lectin concanavalin A. 4) Depolarizing (D-) and biphasic depolarizing/hyperpofarizing (DH -) extrajunctional glutamate potentials were observed using ejection pulses 〉 15 nC. 5) δ-Philanthotoxin (δ-PTX) at concentrations 〉 0.3 Uml-1 inhibited junctional glutamate potentials in a dose-dependent manner, 50% inhibition was achieved using 0.45 Uml-1 δ-PTX. 6) Subthreshold concentrations of proctolin (up to 5 × 10-10M) had no visible effect on glutamate potentials, suggesting that proctolin possibly does not act by modulating glutamate activity. 7) It is proposed that glutamate plays a transmitter role in SL muscles, while the role of proctolin is still unclear.

Additional Material: 7 Ill.