CARDIAC INHIBITION IN DECAPOD CRUSTACEA 



161 



Fig. 15. Potentiation of spii<.e potentials by "inhibition"". Follower neuron of 

 Panulirus. a. Before stimulation, b. Stimulation of the single inhibitor axon 

 reduces burst frequency and duration, via the pacemakers, but lowers the 

 polarization of the follower and hence two spikes occur which were not present 

 before. Note reduced e.p.s.p. c. Only during post-inhibitory rebound does this 

 cell exhibit a spike in absence of "inhibitory"" stimulation. D.The added spikes are 

 not due to the longer interval between bursts because they occur in an escape 

 burst which happens to start soon after the beginning of stimulation (indicated 

 by dots). Calibration, 400 msec, 20 mV. (Courtesy, Terzuolo and Bullock, Arch, 

 iial. Biol. 96 : 117-134, 1958). 



ON - Inhibitor at 



^timuloled ai ^Opef sec 



SponloneouS run 

 and 1 7) epsp's 



Follower burst 

 ( = moinly epsp's) 



.V 



Fig. 16. Effects of membrane potential on inhibitory postsynaptic potentials (/'«//«- 

 linis). A large follower cell is penetrated with a single microelectrode used for 

 both polarizing and recording. The single inhibitory axon is stimulated at 50/sec 

 outside the ganglion. The i.p.s.p. facilitates and then slightly adapts with time. A 

 simultaneous effect on the pacemaker cells elsewhere in the ganglion is seen in the 

 follower bursts which show depression during inhibition (see "plus 15"") and 

 rebound increase following inhibition. (Courtesy, Otani and Bullock, Phvsiol. 

 Zool. 32 : 104-114, 1958). 



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