Abstract
Ciliary ganglia of chick embryos and newly hatched chicks were examined in the light and electron microscopes. Particular attention was given to the fine structure of calyciform synapses, which are characteristically found in ciliary ganglia of birds. The calyciform endings are characterized by large expansions of the presynaptic axons upon ganglion cells, and the terminal processes extend over a considerable area of the cell surface. Often, indeed they appear to envelop the cell. In the electron microscope image, the appositional membranes are separated by a space about 300 to 400 A wide; i.e., the synaptic cleft. At irregularly spaced regions, the appositional membranes show areas of increased density. The presynaptic processes contain clusters of synaptic vesicles, localized at these dense regions. Thus the fine structure complex typical of other synapses is evident. The unique structural features of this synapse are as follows: (a) The calyx or presynaptic terminal derives from a single axon, does not arborize, and terminates upon a single ganglion cell. Thus, unlike the classical bouton terminal, this represents an anatomical device for firing single cells by single axons. (b) The surface area in contiguity, i.e., the area of appositional membranes, is far more extensive than the bouton terminal. The fine structure of this synapse is compared with others, for example, the classical boutons terminaux and purely electrical synapses, in an attempt to correlate fine structure with function.
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Selected References
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- DE LORENZO A. J. Electron microscopic observations of the olfactory mucosa and olfactory nerve. J Biophys Biochem Cytol. 1957 Nov 25;3(6):839–850. doi: 10.1083/jcb.3.6.839. [DOI] [PMC free article] [PubMed] [Google Scholar]
- DE LORENZO A. J. Electron microscopic observations on the taste buds of the rabbit. J Biophys Biochem Cytol. 1958 Mar 25;4(2):143–150. doi: 10.1083/jcb.4.2.143. [DOI] [PMC free article] [PubMed] [Google Scholar]
- DE ROBERTIS E. D., BENNETT H. S. Some features of the submicroscopic morphology of synapses in frog and earthworm. J Biophys Biochem Cytol. 1955 Jan;1(1):47–58. doi: 10.1083/jcb.1.1.47. [DOI] [PMC free article] [PubMed] [Google Scholar]
- FURSHPAN E. J., POTTER D. D. Transmission at the giant motor synapses of the crayfish. J Physiol. 1959 Mar 3;145(2):289–325. doi: 10.1113/jphysiol.1959.sp006143. [DOI] [PMC free article] [PubMed] [Google Scholar]
- PALAY S. L., PALADE G. E. The fine structure of neurons. J Biophys Biochem Cytol. 1955 Jan;1(1):69–88. doi: 10.1083/jcb.1.1.69. [DOI] [PMC free article] [PubMed] [Google Scholar]
- ROBERTSON J. D. The ultrastructure of a reptilian myoneural junction. J Biophys Biochem Cytol. 1956 Jul 25;2(4):381–394. doi: 10.1083/jcb.2.4.381. [DOI] [PMC free article] [PubMed] [Google Scholar]
- SCHULTZ R. L., MAYNARD E. A., PEASE D. C. Electron microscopy of neurons and neuroglia of cerebral cortex and corpus callosum. Am J Anat. 1957 May;100(3):369–407. doi: 10.1002/aja.1001000305. [DOI] [PubMed] [Google Scholar]