PATTERNED ACTIVITIES FROM IDENTIFIABLE 

 "COLD" AND ''WARM" GIANT NEURONS 



(APLYSIA) 



A. Arvanitaki and N. Chalazonitis 



The first demonstration of the existence of specific thermoreceptor units 

 was made by Zotterman, recording from single fibers of the lingual nerve 

 (Zotterman, 1936; Hensel and Zotterman, 1951; Dodt and Zotterman, 

 1952). More recently, evidence has been made available from intracellular 

 recordings made simultaneously from many labelled, identifiable nerve 

 cells in nerve centers of Aplysia (Arvanitaki and Chalazonitis, 1957, 1958, 

 1961 ; Chalazonitis, 1961, 1962). 



Fig. 1. Frequency (spikes per second) as function of the temperature, in a 

 " cold " (o) and a " warm " (#) giant nerve cell of Aplysia. Data from simul- 

 taneous intracellular recordings. The two O^p^ are of extreme range values. 



Under " standard " steady conditions, at 22^C, most of the cells in the 

 isolated ganglion are autoactive in a regular way at frequencies covering 

 a wide spectrum. By plotting frequencies versus temperature, thermal 

 optima (<9^ ;) were revealed. In the diff*erent cells examined 



opt^ 



the 6,^, for 



377 



