Two groups of Golgi tendon organs in cat tibial anterior muscle identified from the discharge frequency recorded under a ramp-and-hold stretch.
Twenty Golgi tendon organs (GTOs) from the tibial anterior muscle of the cat were investigated under a ramp-and-hold stretch of the passive muscle. The stretch rate was varied between 1 and 100 mm/s, the stretch amplitude between 0.1 and 7 mm, the prestretch of the muscle between 0 and 12 mm. The action potential sequences of the GTOs were recorded, and discharge patterns derived from them. The basic discharge frequencies, namely the initial frequency, the peak dynamic discharge, the maximum static value, and the final static value, were read from each discharge pattern. The tension of the muscle was determined at the same points in time at which one of the basic discharge frequencies was read from a discharge pattern. The static and dynamic properties of the GTOs were determined from the basic discharge frequencies. Two groups of GTOs were identified. Four GTOs discharged with an initial frequency and at the same time had static properties of small magnitude. Sixteen GTOs showed no initial activity and had static properties of large magnitude. The two groups of GTOs did not differ in their dynamic properties. The number of alpha-fibers activating a single GTO was determined from a further 11 GTOs. Eight GTOs without initial activity were activated by a mean number of 9.7 alpha-fibers. Three GTOs discharging with initial activity were activated by a mean number of 15.3 alpha-fibers. The two mean values were significantly different (p=0. 02). The identification of two groups of GTOs is explained by the GTOs being positioned differently within the muscle and its tendon.
Schäfer
S S
SS
Medizinische Hochschule Hannover, Abteilung Neurophysiologie 4230, Carl Neuberg Str. 1 D-30625, Hannover, Germany.
Berkelmann
B
B
Schuppan
K
K
D000818:Animals; D002415:Cats; D008465:Mechanoreceptors / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D012026:Reflex, Stretch / Q000502:physiology; D012044:Regression Analysis; D013977:Tibia / Q000502:physiology