Premium
Fine structure of the superficial layers of the viper optic tectum. A golgi and electron‐microscopic study
Author(s) -
Repérant J.,
Peyrichoux J.,
Rio J. P.
Publication year - 1981
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.901990306
Subject(s) - synaptic vesicle , neuropil , vesicle , population , biology , biophysics , electron microscope , synapse , anatomy , postsynaptic potential , neuroscience , optics , central nervous system , biochemistry , physics , demography , receptor , membrane , sociology
The superficial layers of the viper optic tectum, which receive fibers from the retina, were studied using both light and electron microscopes. The optic fibers layer, or stratum opticum , is composed of 200 to 250 tight fascicles containing thin fibers, nearly all of which are myelinated. In the main optic terminal layers, the stratum griseum et fibrosum superficiale , the greatest part of the cellular population is composed of small vertically oriented neurons and horizontal nerve cells, many of which are probably local circuit neurons. The neuropil of the stratum griseum et fibrosum superficiale is made up of small nerve elements, including three types of profiles containing synaptic vesicles: (1) boutons with pleiomorphic synaptic vesicles (P), representing over 47% of the total population of profiles containing synaptic vesicles and comprising three subgroups (P 1 , P 2 , and P 3 ); (2) boutons with spheroidal synaptic vesicles (S), forming more than 29% of the total population of profiles containing synaptic vesicles and comprising two categories, S 1 and S 2 (S 2 , the more numerous, represents the optic boutons, which make up 22% of the total population of profiles containing synaptic vesicles); and (3) dendrites with pleiomorphic vesicles, accounting for approximately 23% of the total population of profiles containing synaptic vesicles. A study of synaptic patterns revealed a large number of serial synapses and a lesser number of triplets or triadic synapses. The presynaptic components are boutons containing spheroidal (S 1 , S 2 ) or pleiomorphic (P 1 , P 2 , P 3 ) synaptic vesicles. The intermediate profile was always a dendrite with synaptic vesicles which frequently belonged to the small neurons of the stratum griseum et fibrosum superficiale . Comparison of the present results with other recent data shows that the synaptic circuitry in the optic tectum of Vipera aspis closely resembles the pattern observed in the optic tectum of other vertebrates, ranging from fish to mammals. However, quantitative differences exist, especially with regard to the proportion of dendrites containing synaptic vesicles. Their number seems to be higher in sauropsidians than in mammals, particularly in primates.