Premium
Afferents of the lamprey optic tectum with special reference to the GABA input: Combined tracing and immunohistochemical study
Author(s) -
Robertson Brita,
Saitoh Kazuya,
Ménard Ariane,
Grillner Sten
Publication year - 2006
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.21078
Subject(s) - tectum , lamprey , biology , neuroscience , posterior commissure , midbrain , pretectal area , superior colliculus , thalamus , diencephalon , gabaergic , anatomy , retrograde tracing , nucleus , commissure , central nervous system , inhibitory postsynaptic potential , fishery
Abstract The optic tectum in the lamprey midbrain, homologue of the superior colliculus in mammals, is important for eye movement control and orienting responses. There is, however, only limited information regarding the afferent input to the optic tectum except for that from the eyes. The objective of this study was to define specifically the γ‐aminobutyric acid (GABA)‐ergic projections to the optic tectum in the river lamprey ( Lampetra fluviatilis ) and also to describe the tectal afferent input in general. The origin of afferents to the optic tectum was studied by using the neuronal tracer neurobiotin. Injection of neurobiotin into the optic tectum resulted in retrograde labelling of cell groups in all major subdivisions of the brain. The main areas shown to project to the optic tectum were the following: the caudoventral part of the medial pallium, the area of the ventral thalamus and dorsal thalamus, the nucleus of the posterior commissure, the torus semicircularis, the mesencephalic M5 nucleus of Schober, the mesencephalic reticular area, the ishtmic area, and the octavolateral nuclei. GABAergic projections to the optic tectum were identified by combining neurobiotin tracing and GABA immunohistochemistry. On the basis of these double‐labelling experiments, it was shown that the optic tectum receives a GABAergic input from the caudoventral part of the medial pallium, the dorsal and ventral thalamus, the nucleus of M5, and the torus semicircularis. The afferent input to the optic tectum in the lamprey brain is similar to that described for other vertebrate species, which is of particular interest considering its position in phylogeny. J. Comp. Neurol. 499:106–119, 2006. © 2006 Wiley‐Liss, Inc.