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Terminal morphology of two branches arising from a single stem‐axon of pretectal (PSm) neurons in the common carp
Author(s) -
Ito Hironobu,
Yoshimoto Masami,
Albert James S.,
Yamane Yoichi,
Yamamoto Naoyuki,
Sawai Nobuhiko,
Kaur Amarjeet
Publication year - 1997
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/(sici)1096-9861(19970217)378:3<379::aid-cne6>3.0.co;2-0
Subject(s) - axon , biology , postsynaptic potential , soma , anatomy , neuroscience , morphology (biology) , synapse , ultrastructure , growth cone , nucleus , receptor , biochemistry , genetics
The induction of postsynaptic structures by presynaptic terminals is suggested in a teleost brain. Neurons in the nucleus pretectalis superficialis pars magnocellularis (PSm) in the common carp are known to send fibers to the corpus mamillare (CM) and the nucleus lateralis valvulae (NLV). Individual axons of PSm neurons bifurcate (or give off an axon collateral), both of which reach the target areas in the CM and NLV. The morphology of horseradish peroxidase‐labeled terminals in the CM and NLV appears quite different in light microscopy. Terminals in the CM appear as a fine network of beaded (2–4 μm in diameter) fibers, while those in the NLV are larger (8–12 μm in transverse diameter) and cup‐shaped, partially enveloping the soma of individual NLV neurons. In electron microscopy, however, these synapses in the CM and NLV share several ultrastructural similarities. Small (0.2 to 0.4‐μm thick, 0.4 to 0.7‐μm long) spine‐like protrusions arising from dendrites in the CM, and from cell bodies in the NLV, invaginate into the axon terminals, and the synaptic junctions are always formed at the base of the protrusion in both areas. Development of this unusual morphology is inferred to be directed from the presynaptic side. The morphological similarity of the spine‐like protrusions to the “spinule,” which is thought to be formed in response to synaptic activation, is discussed. J. Comp. Neurol. 378:379–388, 1997. © 1997 Wiley‐Liss, Inc.