188 



N. CHALAZONITIS 



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Fig. 22. Damped oscillations ending the Br soma activity under the effect of COo. 

 After a depolarization higher than 30 mV, the slow repolarizing phases of the Br 

 soma are abolished and the activity becomes continuous. In this recording one 

 sees the end of the last spike train. The spike amplitude decreases and the activity 

 stops in damped oscillations. Scales: 50 mV, 1 sec. 



A striking effect is commonly seen in this type of cell. The spiking is periodi- 

 cally interrupted by silent intervals resulting from slow (1-2 sec) hyper- 

 polarizing waves, from 30 to 40 mV in amplitude. These are to be seen as 

 reactive waves elicited by the initial CO2 depolarization (Fig. 21 and Fig. 23), 

 and facilitated by the summation of i.p.s.p., probably arising from the CO2- 



' ' i ' ' f 



Fig. 23. The long lasting hyperpolarizing waves'of arhythmic somata. 

 When the arhythmic B soma is CO2 depolarized by no more than about 20-30 

 mV, a hyperpolarizing wave occurs with an amplitude of 30-40 mV and 

 a duration of 1-2 sec. During its falling phase, the activity is completely 

 inhibited and conversely initiated and accelerated during its rising phase. Here 

 also, the frequency is related to the rate of change of the membrane potential 

 rather than to the membrane potential itself. Scales: 25 mV, 1 sec. 



