[Organization of the rhythmic activity of the spinal center motoneurons of the lymphatic hearts of Rana temporaria frogs].

Spontaneous rhythmic impulse discharges of motoneurons of spinal centers of the posterior lymphatic hearts have been recorded from the ventral roots of isolated spinal cord perfused by oxygenated Ringer's solution. Inhibition of the transmission in interneuronal synapses evoked by abolition of Ca ions from the external solution and by the addition to the latter of 1--4 mM EDTA was accompanied by the block of the spontaneous impulse activity. Blocking of rhythmic efferent discharges in the anterior roots was also observed after the addition to normal Ringer's solution of 10--30 mM MgCl2. Inhibition of the spontaneous activity by high Mg content in the perfusion fluid could be alleviated by the addition of 5--15 mM CaCl2 to this solution. Antidromic impulses in the ventral roots of the XI and X segments, evoked by rhythmic electrical stimulation of these roots, did not affect the intrinsic rhythm of motor discharges.