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Fine structure of synapses and retinal innervation of substance P and adenosin deaminase containing neurons in the superior colliculus of the rat
Author(s) -
MiguelHidalgo J. Javier,
Senba Emiko,
Takatsuji Koichi,
Tohyama Masaya
Publication year - 1991
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.903030107
Subject(s) - superior colliculus , postsynaptic potential , biology , retinal , geniculate , neuroscience , enucleation , anatomy , synapse , dendrite (mathematics) , immunoelectron microscopy , eye enucleation , retina , immunohistochemistry , biochemistry , genetics , receptor , nucleus , immunology , geometry , mathematics
The fine structure of substance P (SP) and adenosine deaminase (ADA) immunoreactive structures in synaptic contacts localized to the superficial layers of the superior colliculus of the rat was investigated by means of immunoelectron microscopy. We also examined the possibility of retinal innervation of SP‐ and ADA‐ containing neurons by immunohistochemistry after degeneration of retinal terminals caused by enucleation. SP‐like immunoreactive presynaptic terminals of the stratum griseum superficial (SGS) formed both asymmetric and symmetric synaptic contacts, Presynaptic dendrite like structures were also observed. SP immunoreactive postsynaptic elements made contacts with terminals showing diverse features. ADA‐like immunoreactive structures were seen only as postsynaptic elements to different kinds of nonimmunoreactive terminals and were mostly localized in the ventral third of the SGS and the dorsalmost stratum opticum (SO). After enucleation, degenerating retinal terminals were found to form synaptic contacts with SP and ADA immunoreactive structures. The highest number of such degenerating terminals on ADA immunoreactive structures was observed 2 days after retinal denervation, very few being seen after 5 days. These degenerating terminals were restricted to the ventral SGS and dorsal SO. SP immunoreactive structures postsynaptic to degenerating retinal terminals were most numerous 5 days after enucleation and mainly localized in the dorsal SGS. Occasionally, SP immunoreactive dendrite like processes forming synapses with degenerating retinal terminals were simultaneously presynaptic to other nonimmunoreactive profiles, defining, therefore, serial synapses. The present results suggest that SP‐I and ADA‐I collicular neurons may be part of distinct channels carrying visual information to the lateral posterior and lateral geniculate nuclei of the thalamus, respectively.