TY - JOUR
T1 - Fusimotor responses to fatiguing muscle contractions in non-denervated hindlimb of decerebrate cats
AU - Ljubisavljević, M.
AU - Jovanović, K.
AU - Anastasijević, R.
N1 - Funding Information:
Acknowledgements--This work was supported by a grant from the Serbian Research Foundation. Thanks are due to J. Vuro for both encouragement and criticism.
PY - 1994/8
Y1 - 1994/8
N2 - Changes in discharge rate of 21 fusimotor neurons to medial gastrocnemius muscle during long-lasting fatiguing contractions of lateral gastronemius and soleus muscles were recorded in decerebrate cats with innervation of the same hindlimb preserved. Both the spontaneous activity and reflex responses of fusimotor neurons differed from those found previously in preparations with denervated hindlimb. Higher proportion of units fired at rest at rates above 20 impulses/s, the initial increase in discharge rate at the onset of muscle contraction was markedly prolonged, lasting in the majority of units throughout the muscle contraction, while the late increase in discharge rate developing with muscle fatigue was either absent or short-lasting. It is suggested that the increase in spontaneous firing rate occurs in dynamic fusimotor neurons being supported by afferent inflow from secondary muscle spindle endings from non-contracting muscles, the enhancement of the early responses to be primarily due to recurrent disinhibition and the differences in changes of early and late responses to reflect their partly different origin. The possibility is raised that the late reflex responses are lacking more often in static than in dynamic fusimotor neurons. From the functional point of view the differences in fusimotor reflex responses in innervated versus denervated hindlimb may indicate their susceptibility to modifications by changes in afferent inflow according, supposedly, to the current demands of motor control of the active and/or fatigued muscle.
AB - Changes in discharge rate of 21 fusimotor neurons to medial gastrocnemius muscle during long-lasting fatiguing contractions of lateral gastronemius and soleus muscles were recorded in decerebrate cats with innervation of the same hindlimb preserved. Both the spontaneous activity and reflex responses of fusimotor neurons differed from those found previously in preparations with denervated hindlimb. Higher proportion of units fired at rest at rates above 20 impulses/s, the initial increase in discharge rate at the onset of muscle contraction was markedly prolonged, lasting in the majority of units throughout the muscle contraction, while the late increase in discharge rate developing with muscle fatigue was either absent or short-lasting. It is suggested that the increase in spontaneous firing rate occurs in dynamic fusimotor neurons being supported by afferent inflow from secondary muscle spindle endings from non-contracting muscles, the enhancement of the early responses to be primarily due to recurrent disinhibition and the differences in changes of early and late responses to reflect their partly different origin. The possibility is raised that the late reflex responses are lacking more often in static than in dynamic fusimotor neurons. From the functional point of view the differences in fusimotor reflex responses in innervated versus denervated hindlimb may indicate their susceptibility to modifications by changes in afferent inflow according, supposedly, to the current demands of motor control of the active and/or fatigued muscle.
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U2 - 10.1016/0306-4522(94)90444-8
DO - 10.1016/0306-4522(94)90444-8
M3 - Article
C2 - 7969938
AN - SCOPUS:0028124756
SN - 0306-4522
VL - 61
SP - 683
EP - 689
JO - Neuroscience
JF - Neuroscience
IS - 3
ER -