168 



DONALD M. MAYNARD 



Fig. 22. Inhibition of spontaneous ganglion activity, unit analysis of total burst 

 (Poniilinis). Units 1, 2 and 3 are small neurons. The pattern of each small unit 

 during a burst is plotted in a separate column. The vertical scale represents 

 impluse frequency, the horizontal, time. Dashed lines represent the interval 

 between the first impulse of unit 1 (0 time) and the first activity in units 2 or 3. 

 The figures in the large unit column give the interval on 0- 1 sec between unit 1 

 activity and the appearance of large cell inpulses. Inhibitor stimulation at 36/sec 

 began between bursts 3 and 4 and ended in the middle of burst 19 



(Maynard, 1954). 



of inhibitor impulses than the first. There is no maintained potential change 

 in the soma between such trains. 



One of the most obvious differences between inhibition of the single 

 spontaneous unit and inhibition of the heart beat is the frequent apparent 

 absence of post-inhibitory rebound in the latter. Although in some of the 

 published cases this might be caused by after discharge in the inhibitor 

 fiber, in others (see Fig. 17) a beat just at the end of inhibition with subsequent 

 reduction in heart rate makes such explanations involving experimental 

 artifact unlikely. Among the many circumstances which can lead to apparent 

 suppression of rebound, two may be described. 



In one preparation, the latent pause of the large units proved so much 

 longer than that of the small, that the large units were often absent from the 

 first post-inhibitory burst. The excitability of the small units was increased 

 only in the first post-inhibitory burst (indicated by more inipulses per burst), 

 while the excitability of the large units was increased only in the second 

 post-inhibitory small unit burst (indicated by decreased latency). The total 



