EXCITATORY AND INHIBITORY PROCESSES 

 IN CRUSTACEAN SENSORY NERVE CELLS* 



C. Eyzaguirre 



Department of Physiology, University of Utah College of Medicine, 

 Salt Lake City, Utah 



Since Alexandrowicz's original description (1951, 1952), a number of papers 

 have dealt with the properties of sensory nerve cells located in the abdomen 

 and in the thorax of lobsters and crayfish. In addition, this subject has been 

 reviewed recently by Kulfler (1958, 1960) and Edwards (1960); see also 

 Eccles (1957). 



The purpose of this paper is to review once more, from a rather personal 

 point of view, some of the functional properties of these crustacean nerve 

 cells. Whenever possible, an effort has been made to avoid overlap with 

 material already covered by other reviewers. 



A. THE CRUSTACEAN SENSORY NERVE CELLS 



In general these cells have their soma near receptor muscle elements; their 

 dendrites approach the muscles and become embedded in their mass. The 

 axon emerges from the pole opposite to that facing the receptor muscle and, 

 following a relatively long trajectory, reaches the ventral cord. This view of 

 these neurons is valid only for the more commonly occurring "receptor 

 organs" of Alexandrowicz. In fact, other receptor cells (N-cells) also occur 

 in these animals (Alexandrowicz, 1952) and are quite diflferent. They are 

 very small, with long and intricate dendritic processes which reach ordinary 

 muscles. Some of these dendrites emerge from the axon at some distance 

 from the soma. The function of the N-cells has been investigated only 

 recently (Pilgrim and Wiersma, 1960); most of the attention has been focused 

 on the larger "receptor organ" cells. 



From the start one is faced with the question of describing the cell in 



accordance to the classical components, axon, soma and dendrites. In 



morphological terms the soma is usually defined as a prominent region 



containing the nucleus while dendrites are non-axonal processes emerging 



from the cell. In crustacean sensory nerve cells the region containing the 



* Supported by a Senior Research Fellowship (SF-260) from the U.S. Public Health 

 Service and by grant NSF G-9952 from the National Science Foundation. 



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