Abortive Spikes of the Frog Muscle Spindle

Initiation of Nerve Impulses Inthe Frog Muscle Spindle

“…It is concluded that all the monophasic potentials are due to dispersed currents from the origin toward the parent axon with a length constant of approximately 2.5mm, as has been calculated for the abortive spike (ITO, 1969). This conclusion also supports an assumption that the large monophasic potential may be the first component itself or a part of it as classified in the preceding section.…”

“…Effect of change in length of paraffin gap on the configuration of impulse When spontaneous afferent impulses were recorded across a paraffin gap of 2 mm length situated at a distance within 1 mm from the capsule of an isolated spindle, triphasic potential changes (negative-positive-negative with respect to the nerve ending) were always observed, as illustrated in The first negative potential rose from a discrete step (a prepotential), and was followed by a small positive and then a residual negative potential, as has been shown by KATZ (1950a) and ITO (1969). When the length of the paraffin gap was increased to 3 or 5 mm with 1 mm distance from the capsule to the gap, a notch appeard early in the de-crement phase of the first negative potential, as illustrated in FIG.…”

“…The technique employed was essentially the same as that described previously (ITO, 1969). Forty five isolated muscle spindle preparations were excised mainly from sartorius muscles and, in a few cases, from semitendinosus muscles of frogs…”

Drug-Induced Modulation of the Positive Afterpotential Following the Propagated Impulse and of the Discharge Pattern in the Frog Muscle Spindle

“…A previous work (1) has shown that an individual propagated impulse recorded at the sensory nerve terminal of the frog muscle spindle was always followed by a long-lasting positivity of up to 0.1 sec in duration and of 0.1-0.3 mV in the maximal amplitude, during which the appearance of propagated and abortive spikes was suppressed. Time course of the positive after-potential was similar to that of the after-hyperpolarization following spike discharge of amphibian motoneuron, during which excitatory processes were de pressed (2).…”

“…The paraffin pool was situated in a slit of 1 mm at the center of a par tition between the two Ringer's pools. The paraffin gap method has been described in detail elsewhere (1). A pair of calomel electrodes were inserted into subsidiary Ringer's pools, each of which was connected with RA and RB by means of two Ringer's agar bridges.…”