STUDIES ON THE ULTRASTRUCTURE AND 



HISTOPHYSIOLOGY OF CELL MEMBRANES, NERVE 



FIBERS AND SYNAPTIC JUNCTIONS IN 



CHEMORECEPTORS* 



A. J. D. DE Lorenzo 



The Johns Hopkins University School of Medicine and the Marine Biological 

 Laboratory, Woods Hole, Massachusetts 



Recent years have witnessed a revival of interest in sensory receptors, 

 due in large part to the sensory physiologists. The studies of Kuffler, 

 Fuortes, Beidler, Loewenstein and others have provided functional analyses 

 of excitable membranes, receptive fields and feedback circuits in sensory 

 transducers. These studies represent one of the most exciting areas of 

 contemporary neurophysiology. Unfortunately, morphological investiga- 

 tions of sensory receptors and their synaptic junctions have not kept pace 

 with the rapid advances in sensory physiology. 



This is particularly true of the chemoreceptors. Contemporary text- 

 books and modern reviews laboriously reproduce drawings of Schwalbe, 

 Koelliker, Kolmer and others and attempt to ascribe the properties of 

 generator potentials, synaptic potentials and electrochemical gradients to 

 nineteenth-century histology. To a large extent, the paucity of morpho- 

 logical descriptions of these regions, derives from the serious limitations 

 of staining small unmyelinated nerve fibers with silver salts. Electron 

 microscopy resolves most of these difficulties. 



This presentation will be limited to our work on the olfactory and 

 gustatory pathways with particular emphasis on the fine structure and 

 histophysiology of nerve fibers and synaptic junctions. All the data have 

 been derived from examination of rabbit tissues. 



THE OLFACTORY PATHWAY 



Conventional silver staining of the olfactory mucosa and examination 

 with the light microscope reveals a great deal of information regarding the 

 microscopic organization of olfactory epithelium. Figures 1 and 2 are 



* These studies were supported by Grants NB-2173 and NB-2182 from the National 

 Institute of Neurological Diseases and Blindness, United States Public Health Service. 

 A travel grant from the National Science Foundation is also gratefully acknowledged. 



