The responses of secondary endings of cat soleus muscle spindles to succinyl choline

1994 ◽  
Vol 100 (1) ◽  
Author(s):  
A. Taylor ◽  
D.L. Morgan ◽  
J.E. Gregory ◽  
U. Proske
Keyword(s):  
Soleus Muscle ◽  
Muscle Spindles ◽  
Succinyl Choline

Sympathetic outflow enhances the stretch reflex response in the relaxed soleus muscle in humans

2005 ◽  
Vol 98 (4) ◽  
pp. 1366-1370 ◽  
Author(s):  
Nis Hjortskov ◽  
Jørgen Skotte ◽  
Christian Hye-Knudsen ◽  
Nils Fallentin
Keyword(s):  
Soleus Muscle ◽  
Stretch Reflex ◽  
Mental Arithmetic ◽  
Muscle Spindles ◽  
Short Latency ◽  
Reflex Response ◽  
Sympathetic Outflow ◽  
Direct Influence ◽  
Handgrip Exercise ◽  
Sympathetic Nervous

Animal experiments suggest that an increase in sympathetic outflow can depress muscle spindle sensitivity and thus modulate the stretch reflex response. The results are, however, controversial, and human studies have failed to demonstrate a direct influence of the sympathetic nervous system on the sensitivity of muscle spindles. We studied the effect of increased sympathetic outflow on the short-latency stretch reflex in the soleus muscle evoked by tapping the Achilles tendon. Nine subjects performed three maneuvers causing a sustained activation of sympathetic outflow to the leg: 3 min of static handgrip exercise at 30% of maximal voluntary contraction, followed by 3 min of posthandgrip ischemia, and finally during a 3-min mental arithmetic task. Electromyography was measured from the soleus muscle with bipolar surface electrodes during the Achilles tendon tapping, and beat-to-beat changes in heart rate and mean arterial blood pressure were monitored continuously. Mean arterial pressure was significantly elevated during all three maneuvers, whereas heart rate was significantly elevated during static handgrip exercise and mental arithmetic but not during posthandgrip ischemia. The peak-to-peak amplitude of the short-latency stretch reflex was significantly increased during mental arithmetic ( P < 0.05), static handgrip exercise ( P < 0.001), and posthandgrip ischemia ( P < 0.005). When expressed in percent change from rest, the mean peak-to-peak amplitude increased by 111 (SD 100)% during mental arithmetic, by 160 (SD 103)% during static handgrip exercise, and by 90 (SD 67)% during posthandgrip ischemia. The study clearly indicates a facilitation of the short-latency stretch reflex during increased sympathetic outflow. We note that the enhanced stretch reflex responses observed in relaxed muscles in the absence of skeletomotor activity support the idea that the sympathetic nervous system can exert a direct influence on the human muscle spindles.

Correlating resting discharge with small signal sensitivity and discharge variability in primary endings of cat soleus muscle spindles

1994 ◽  
Vol 71 (1) ◽  
pp. 309-316 ◽  
Author(s):  
J. J. Scott ◽  
J. E. Gregory ◽  
U. Proske ◽  
D. L. Morgan
Keyword(s):  
Soleus Muscle ◽  
Wave Amplitude ◽  
Muscle Length ◽  
Muscle Spindles ◽  
Sine Wave ◽  
Small Signal ◽  
Signal Sensitivity ◽  
Maximum Body ◽  
Maximum Body Length ◽  
Conditioning Contraction

1. In a previous report we proposed that primary endings of cat soleus muscle spindles can be separated into two kinds. One kind, called by us silent endings, at muscle lengths shorter than Lm -10 (maximum body length -10 mm), fell silent after a 5 mm shortening step. Spontaneous endings, on the other hand, were able to resume a resting discharge after a brief pause at all muscle lengths down to Lm -20. This report examines further differences between the two kinds of endings. 2. There were consistent differences in the muscle length dependence of the maintained level of resting discharge of the two kinds of endings, measured after a conditioning contraction or a contraction followed by a shortening step. The resting discharge of spindles with spontaneous endings, after both forms of conditioning increased progressively with length. For silent endings, after a conditioning contraction, resting discharge fell slightly at longer lengths. 3. Discharge variability, measured at a number of muscle lengths, showed a dependence both on mean interimpulse interval and on spindle type, being higher in silent than spontaneous spindles. 4. Small signal sensitivity was measured with the use of 1 Hz sinusoidal stretches applied longitudinally to the tendon. Sine wave amplitude was adjusted to give a 30% depth of modulation of the resting discharge. Spontaneous endings were consistently less sensitive to the stretches than silent endings at all muscle lengths. Average sensitivities, measured over a range of lengths between Lm -4 and Lm -20 mm were 0.30 imp.s-1.microns -1 for spontaneous endings and 0.66 imp.s-1.microns -1 for silent endings.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Expression of Myosin Heavy Chain Isoforms Along Intrafusal Fibers of Rat Soleus Muscle Spindles After 14 Days of Hindlimb Unloading

2002 ◽  
Vol 50 (11) ◽  
pp. 1543-1553 ◽  
Author(s):  
L. De-Doncker ◽  
F. Picquet ◽  
G. Butler Browne ◽  
M. Falempin
Keyword(s):  
Soleus Muscle ◽  
Muscle Spindles ◽  
Myosin Heavy Chain Isoforms ◽  
Hindlimb Unloading ◽  
Cross Sectional ◽  
Intrafusal Fibers ◽  
Significant Difference ◽  
Slow Type ◽  
Rat Soleus Muscle

Morphological, contractile, histochemical, and electrophoretical characteristics of slow postural muscles are altered after hindlimb unloading (HU). However, very few data on intrafusal fibers (IFs) are available. Our aim was to determine the effects of 14 days of hindlimb unloading on the morphological and immunohistochemical characteristics of IF in rat soleus muscle. Thirty-three control and 32 unloaded spindles were analyzed. The number and distribution of muscle spindles did not appear to be affected after unloading. There was no significant difference in number, cross-sectional area, and histochemical properties of IF between the two groups. However, after unloading, a significant decrease in slow type 1 MHC isoform and a slight increase in slow-tonic MHC expression were observed in the B and C regions of the bag1 fibers. The α-cardiac MHC expression was significantly decreased along the entire length of the bag2 fibers and in the B and C regions of the bag1 fibers. In 12 muscle spindles, the chain fibers expressed the slow type 1 and α-cardiac MHC isoforms over a short distance of the A region, although these isoforms are not normally expressed. The most striking finding of the study was the relative resistance of muscle spindles to perturbation induced by HU.

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