308 



C. EYZAGUIRRE 



Fig. 17. Post-inhibitory excitation. Fast receptor cell stretched to near firing 

 level, (a) Extracellular recording. Between arrows inhibitory stimuli at 23/sec 

 are followed by afferent discharge, (b). Intracellular record. Six inhibitory impulses 

 are followed by one conducted impulse. (From Kuffler and Eyzaguirre, J. Gen. 

 Physio/. 39 : 155-184, 1955.) 



Interaction of Antidromic and Inhibitory Activity 



Antidromic impulses normally invade the soma-dendrite complex. Their 

 repolarizing phase has been analyzed and compared with inhibitory potentials 

 set up either independently or during this repolarization phase. With this 

 type of experiment, information has been obtained as to the extent of 

 dendritic invasion by an antidromic impulse. 



If the preparation is stretched, orthodromic discharges are initiated. The 

 repolarization phase of the orthodromic impulses brings the membrane 

 potential back to less than several millivolts from the resting potential of 

 the relaxed cell. If an antidromic impulse invades one of these cells its 

 repolarization phase is similar to that of the orthodromic impulse. However, 

 in a cell which has its membrane potential reduced by stretch, stimulation of 

 an inhibitory fiber hyperpolarizes the cell to levels below those obtained 

 following orthodromic or antidromic impulses (Fig. 18). This indicates very 

 clearly the following: (1) Since inhibitory impulses may repolarize cells 

 further than the recovery stage of antidromic or orthodromic impulses it is 



