title: Frequencygrams of rabbit spindle primary endings elicited by stimulation of fusimotor fibres.
abstract: 1. Frequencygrams of rabbit spindle primary endings elicited by stimulation of single fusimotor axons were obtained by the method described by Bessou, Laporte & Pagès (1968a) which gives indirect information on the contraction of intrafusal muscle fibres.2. Repetitive stimulation of the majority of static axons (twenty out of twenty-five axons studied) gave frequencygrams showing discrete large peaks corresponding to each stimulus, even for rates of stimulation as high as 300-500/sec.3. Large responses to single stimuli were elicited by thirteen of these axons. The responses consisted of a fast-rising phase lasting 5-10 msec and declining phase lasting 30-50 msec.4. Repetitive stimulation of some static axons (five out of twenty-five) gave frequencygrams displaying a smooth contour with no sign of individual responses to single stimuli and with a slow rising and declining phase.5. Both kinds of ;static' frequencygrams may be obtained from the same spindle.6. Repetitive stimulation of dynamic axons gave frequencygrams of small amplitude with a slow rising and declining phase and no sign of individual responses, even at low rates of stimulation.7. Although rabbit spindles lack nuclear chain muscle fibres (Barker & Hunt, 1964), rabbit's frequencygrams were essentially similar to those of cat spindles. The functional implications of this similarity are discussed.
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology; D004594:Electrophysiology; D009046:Motor Neurons / Q000502:physiology*; D009119:Muscle Contraction; D009470:Muscle Spindles / Q000502:physiology*; D009411:Nerve Endings / Q000502:physiology*; D009431:Neural Conduction; D011817:Rabbits; D013997:Time Factors