CHEMOPOTENTIALS IN GIANT NERVE CELLS 

 {APLYSIA FA SCI ATA) 



N. Chalazonitis 



Centre National de la Recherche Scientifique, Laboratoire d'Electrobiologie EPHE, 

 Faculte des Sciences, Universite de Lyon, France 



INTRODUCTION 



In this treatment, we mean by chemopotentials the changes in the electrical 

 activity of nerve cells elicited by a variation in the concentration of CO2, O2, 

 H+ or OH~. More generally, the term chemopotentials may refer to such 

 electrical changes as are elicited by a variation in the concentration of any 

 metabolite, provided that its action is reversible. Most often, the effects of 

 anoxia or CO2 on nerve fibres are inhibitory (Gerard, 1932; Lorente de No, 

 1947; Monnier, 1952; Laget and Legouix. 1951; Coraboeuf, 1951; Arvani- 

 taki and Chalazonitis, 1954; Meves, 1955; Straub, 1956). The excitability of 

 the ganglionic chain of some insects seems to be increased by CO2 (Boistel 

 et al., 1957). 



Excitatory actions are well known on some mammalian nerve centres such 

 as the respiratory centre, the carotid body, the aorta paraganglia (Heymans, 

 1953; von Euler et al., 1939; von Euler and Soderberg, 1952; Gernandt, 

 1946; Witzleb and Bartels, 1956; Zotterman, 1953), and in some other 

 centres less specialized for CO'2 reception (Bremer and Thomas, 1936; Sugar 

 and Gerard, 1938; Dell and Bonvallet, 1956; Van Harreveld, 1946; Lloyd, 

 1952-1953; Kolmodin and Skoglund, 1959; Chalazonitis and Sugaya, 

 1958a, b; Chalazonitis, 1959). 



In the present study the effects of anoxia and CO2 enrichment in Aplysia 

 nerve cells will be discussed. The spontaneous activity of such cells may last 

 many hours and is easily monitored by microelectrodes. The spontaneous 

 activity of invertebrate nerve cells has been studied extensively by a number 

 of authors (Arvanitaki and Chalazonitis, 1955; Bullock, 1958; Bullock and 

 Terzuolo, 1957; Tauc, 1960; among others). 



Preliminary studies on the effects of anoxia and CO2 on spontaneous 

 activity in Aplysia nerve cells have already been pubUshed (Chalazonitis and 

 Sugaya, 1958a, b). In this paper the excitatory actions of anoxia and COg 

 will be only briefly mentioned. More space will be devoted to pointing out 

 some of the inhibitory effects, particularly in relation to the three types of 

 electrical activity recognized among the different identifiable cells of Aplysia 



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