Effect of differential blocking of motor axons on antidromic activation of Renshaw cells in the cat

M. Kato; K. Fukushima

doi:10.1007/bf00234008

Discharge patterns of phrenic motoneurons during fictive coughing and vomiting in decerebrate cats

Journal of Applied Physiology ◽

10.1152/jappl.1992.73.4.1626 ◽

1992 ◽

Vol 73 (4) ◽

pp. 1626-1636 ◽

Cited By ~ 25

Author(s):

S. Milano ◽

L. Grelot ◽

A. L. Bianchi ◽

S. Iscoe

Keyword(s):

Interspike Interval ◽

Discharge Frequency ◽

Motor Axons ◽

Antidromic Activation ◽

Phrenic Motoneurons ◽

Active Motor ◽

Recruitment Order ◽

Discharge Patterns ◽

Decerebrate Cats

In decerebrate, paralyzed, and ventilated cats, we recorded the activity of 100 spontaneously active phrenic motor axons during the increased phrenic discharges characteristic of fictive vomiting (FV) and coughing (FC). During control respiratory cycles, approximately one-half the neurons were recruited in the first decile of inspiration; recruitment continued throughout inspiration. During FV, the duration of phrenic discharge was halved; 20 of 26 motoneurons studied were recruited in the first decile of the burst. During FC, recruitment times did not change compared with control, although the duration of the phrenic burst doubled. Discharge frequencies increased and recruitment order of phrenic motoneurons was virtually unaffected during FC and FV. Limited recruitment of previously inactive neurons in the filaments from which we recorded was found during FV and FC. During FV, 1 previously inactive motoneuron was recruited in 16 filaments containing 25 spontaneously active motor axons. During FC, 3 new motoneurons were recruited in addition to the 64 already active in 35 filaments. Recruitment during FV and FC was absent even when recording from filaments known, on the basis of antidromic activation, to contain inactive motor axons. During FV, 10 of 26 motoneurons began their discharges with doublets (interspike interval < 10 ms); doublets occurred in only 4 of 67 motoneurons during FC. Already active phrenic motoneurons contributed to the intense phrenic activity associated with both respiratory (coughing) and nonrespiratory (vomiting) behavior by increases in discharge frequency, earlier recruitment, and doublets; the contribution of previously quiescent motoneurons remains uncertain.

Download Full-text

Field potentials of alpha and gamma motoneurons and Renshaw cells in response to activation of motor axons

Experimental Neurology ◽

10.1016/0014-4886(69)90071-5 ◽

1969 ◽

Vol 25 (1) ◽

pp. 57-69 ◽

Cited By ~ 15

Author(s):

W.D. Willis ◽

R.D. Skinner ◽

M.A. Weir

Keyword(s):

Renshaw Cells ◽

Field Potentials ◽

Motor Axons

Download Full-text

Facilitation and depression in the responses of spinal Renshaw cells to random stimulation of motor axons

Journal of Neurophysiology ◽

10.1152/jn.1988.60.5.1638 ◽

1988 ◽

Vol 60 (5) ◽

pp. 1638-1652 ◽

Cited By ~ 15

Author(s):

U. Windhorst ◽

R. Rissing ◽

J. Meyer-Lohmann ◽

Y. Laouris ◽

U. Kuipers

Keyword(s):

Renshaw Cells ◽

Motor Axons ◽

Synaptic Coupling ◽

Rate Reduction ◽

Reference Time ◽

Input Channel ◽

Stimulus Rate ◽

Cell Responses ◽

Renshaw Cell ◽

The Mean

1. We investigated the responses of cat lumbosacral Renshaw cells to pseudo-Poison stimulus sequences (of three different mean rates) delivered to motor axons in ventral roots or various muscle nerves. The Renshaw cell responses were evaluated by computation of peristimulus time histograms (PSTHs). 2. PSTHs computed with respect to all the stimuli showed, before the reference time, near-constant bin contents corresponding to the mean firing probability (rate), and an initial excitatory component (increase in discharge probability) after the reference time, followed by a small but longer-lasting reduction of firing rate. These two response components were strongly correlated linearly. It is suggested that the postexcitatory rate reduction is predominantly due to afterhyperpolarization. 3. In general, Renshaw cell responses to any stimulus in a stimulus train depended upon the stimulation history. In the averaged record, the response to the second of a pair of stimuli was affected by the first stimulus independently of intervening (random) stimuli. Very often, the second response showed a long-lasting depression (from 25 to greater than 250 ms). In a number of cases a briefer facilitating effect preceded the depression. 4. These conditioning effects were largely homosynaptic, i.e., confined to the particular input channel that was stimulated. This was shown by stimulating two different nerves (or nerve branches) with independent random patterns of similar mean rates and determining the cross-conditioning exerted by one input channel on the excitatory effects of the other. At small intervals between conditioning and test stimuli of some tens of milliseconds, a facilitatory effect could often be seen, which almost certainly reflected spatial summation. However, the subsequent depressant effect was largely accounted for by the postexcitatory rate reduction consequent to the conditioning stimulus in the parallel channel. Autoconditioning was still present. 5. The amount of facilitation and depression as well as their balance depended on the average Renshaw cell response. This in turn depended, at each mean stimulus rate, on the strength of synaptic coupling between an input channel and the cell, and on the mean stimulus rate, declining with an increase in mean rate. That is, the facilitation increased and the depression decreased with decreasing synaptic coupling and increasing mean stimulus rate. 6. Several factors may contribute to facilitation and depression; these are discussed with respect to their relative quantitative significance.(ABSTRACT TRUNCATED AT 400 WORDS)

Download Full-text