The response of de‐efferented muscle spindle endings in the cat's soleus to slow extension of the muscle

Abstract

The relation between the frequency of discharge of a muscle spindle ending and the extension applied to the muscle has been studied under various conditions (Eldred, Granit & Merton, 1953;Granit, 1958;Granit & Homma, 1959a; Whitteridge, 1959;Eldred, Lindsley & Buchwald, 1960). There has not, however, been any comparison of the properties of the primary and of the secondary afferent endings of the muscle spindle in this respect; nor is it known whether Whitteridge's finding for spindles in eye muscles, that intrafusal fibre contraction may increase the sensitivity of an ending to stretch, also holds for either the primary or the secondary endings of spindles in limb muscles. These points have, therefore, been investigated in the present work. The frequency-extension relations were determined under dynamic conditions by recording the discharge of an ending while the muscle was slowly stretched at a constant velocity. The use of this method showed incidentally that for de-efferented spindles the response of primary endings to the phasic component of the stretch is much more marked than that of secondary endings. This confirms the findings of Cooper (1959) for spindles with an intact motor supply. METHODS Preparation. The experiments were performed on 23 cats. One was decerebrated and the rest were anaesthetized with pentobarbitone sodium (Nembutal; Abbott Laboratories) given intraperitoneally. The discharge of single afferents from muscle spindle endings lying in the right soleus muscle was recorded from thin dorsal root filaments. Soleus was completely isolated from the spinal cord by cutting the L 6, L 7, S 1 and S2 dorsal and ventral roots. The nerves to most other leg and hip muscles, including the lateral head of gastrocnemius, were cut.Myography and application of 8tretch. The right tibia was fixed rigidly by pins and the tension in soleus recorded from the cut Achilles tendon by an isometric myograph which could be moved so as to extend soleus. The movement was at constant velocity, variable from about 0 5 mm/sec to about 9 mm/sec, and was produced by a screw thread driven by a speed-controlled motor. The extension was monitored by means of a microswitch which * M.R.C. Scholar.

The effects of dimethothiazine on muscle spindle activity in the decerebrate cat

“…The conduction distance was determined at the end of the experiment by dissecting out the sciatic nerve with its attached dorsal roots. The possible source of error in determination of conduction velocities discussed by Harvey & Matthews (1961) did not appear to occur in the present series of experiments.…”

“…The range of conduction velocities observed in these experiments was from 110 to 30 m/s. A conduction velocity of 70 m/s has been taken as the dividing line between afferents from primary and afferents from secondary endings (Harvey & Matthews, 1961). On this basis, fifteen experiments were on primary endings and seven on secondary endings in preparations with intact ventral roots.…”

Processing Afferent Proprioceptive Information at the Main Cuneate Nucleus of Anesthetized Cats

“…Neurons were considered to respond to activated muscle proprioceptors when they (1) were sensitive to sinusoidal muscle stretching (Lundberg and Winsbury, 1960;Bianconi and van der Meulen, 1963;Brown et al, 1967;Matthews and Stein, 1969;Stuart et al, 1970;Mackie et al, 1998), showing a tight phase locking at the tested frequencies of 130 -135 Hz (Mackie et al, 1998); (2) produced spike bursting during stretching, a rapid drop in discharge on completion of the dynamic phase of stretching, and then a relatively slow drop during the holding phase (Matthews, 1933;Harvey and Matthews, 1961;Matthews, 1981;Edin and Vallbo, 1990); and (3) showed silenced firing during muscle shortening (stretch release) (Matthews, 1981;Edin and Vallbo, 1990;Grill and Hallet, 1995). It became clear during the first successful experiments in three distinct animals that cells responding in a 1:1 fashion to 130 -135 Hz muscular sinusoidal vibration also responded to manual muscle stretch (by flexing or extending the appropriated articulation), showing bursting discharges during the dynamic phase of stretching followed by a fall in discharge rate during holding and silenced firing during shortening.…”

The Effects of Trimethadione on Pentetrazol‐induced Discharges of Primary Muscle Spindle Afferents From the Hind Limb of the Rat

“…That is, the decrease in frequency which occurs in the first 500 ms after completion of a ramp and hold stretch (Harvey & Matthews, 1961;Crowe & Matthews, 1964). These were superimposed on previously determined curves for primary and secondary muscle spindle afferents (Angel & Clarke, 1980a firing to stretch before and after PTZ were constructed.…”

“…Ramp and hold stretches were employed to allow changes in dynamic index to be measured (Harvey & Matthews, 1961;Brown & Matthews, 1966). An increase in dynamic index was taken to indicate predominant yd activity and a decrease predominant ys activity.…”