Excitatory and InhibitoryTransmission from the Optic Tectum to Nucleus Isthmi and Its Vicinity in Amphibians

1995 ◽  
Vol 46 (1) ◽  
pp. 43-49 ◽  
Author(s):  
Gang-Yi Wu ◽  
Shu-Rong Wang
Keyword(s):  
Optic Tectum ◽  
Nucleus Isthmi

GABAergic visual pathways in the frog Rana pipiens

2001 ◽  
Vol 18 (3) ◽  
pp. 457-464 ◽  
Author(s):  
ZHENG LI ◽  
KATHERINE V. FITE
Keyword(s):  
Optic Tectum ◽  
Rana Pipiens ◽  
Visual Pathways ◽  
Second Order ◽  
Gamma Aminobutyric Acid ◽  
Nucleus Isthmi ◽  
Double Labeling ◽  
Inhibitory Neurotransmitter ◽  
Vertebrate Brain ◽  
Pretectal Nucleus

Gamma-aminobutyric acid (GABA) is the most prevalent inhibitory neurotransmitter in the vertebrate brain. It can exert its influence either as GABAergic projection pathways or as local interneurons, which play an essential role in many visual functions. However, no GABAergic visual pathways have been studied in frogs so far. In the present study, GABAergic pathways in the central visual system of Rana pipiens were investigated with double-labeling techniques, combining immunocytochemistry for GABA with Rhodamine microspheres for retrograde tracing. Three GABAergic visual pathways were identified: (1) a retino-tectal projection, from retina to the contralateral optic tectum (OT); (2) an ipsilateral projection from the nucleus of the basal optic root (nBOR) to the pretectal nucleus lentiformis mesencephali (nLM); and (3) a second-order pathway from the nucleus isthmi (NI), bilaterally, to the optic tectum. These results indicate that GABA is involved in both first-order (retina to optic tectum) as well as second-order (nucleus isthmi to optic tectum) visual projections in Rana pipiens, and may play a major role in mediating visuomotor reflexs such as optokinetic nystagmus or other visually guided behaviors.

Dual actions of isthmic input to tectal neurons in a reptile, Gekko gekko

1999 ◽  
Vol 16 (5) ◽  
pp. 889-893 ◽  
Author(s):  
STEPHEN A. GEORGE ◽  
GANG-YI WU ◽  
WEN-CHANG LI ◽  
SHU-RONG WANG
Keyword(s):  
Electrical Stimulation ◽  
Optic Nerve ◽  
Optic Tectum ◽  
Nucleus Isthmi ◽  
Postsynaptic Potentials ◽  
Tectal Neurons ◽  
Electrical Connections ◽  
Stimulation Of

We analyzed postsynaptic potentials and dye-labeled morphology of tectal neurons responding to electrical stimulation of the optic nerve and of the nucleus isthmi in a reptile, Gekko gekko, in order to compare with previously reported interactions between the optic tectum and the nucleus isthmi in amphibians and birds. The results indicate that isthmic stimulation exerts inhibitory and excitatory actions on tectal cells, similar to dual isthmotectal actions in amphibians. It appears that dual actions of the isthmotectal pathway in amphibians and reptiles are shared by two subdivisions of the nucleus isthmi in birds. The morphology of tectal cells responding to isthmic stimulation is generally similar to that of tectoisthmic projecting neurons, but they differ particularly in that some tectoisthmic cells bear numerous varicosities whereas cells receiving isthmic afferents do not. Thus, it is likely that at least some tectoisthmic cells may not be in the population of tectal cells that can be affected by isthmic stimulation. Forty-four percent of injections resulted in dye-coupled labeling, suggesting extensive electrical connections between tectal cells in reptiles.

Topographic projections between the nucleus isthmi and the optic tectum in a teleost,Navodon Modestus

1981 ◽  
Vol 224 (2) ◽  
pp. 225-234 ◽  
Author(s):  
Noboru Sakamoto ◽  
Hironobo Ito ◽  
Shinsuke Ueda
Keyword(s):  
Optic Tectum ◽  
Nucleus Isthmi

Avian nucleus isthmi ventralis projects to the contralateral optic tectum

1989 ◽  
Vol 481 (1) ◽  
pp. 181-184 ◽  
Author(s):  
S. Martínez ◽  
L. Puelles
Keyword(s):  
Optic Tectum ◽  
Nucleus Isthmi

Afferent connectivity to different functional zones of the optic tectum in goldfish

2003 ◽  
Vol 20 (4) ◽  
pp. 397-410 ◽  
Author(s):  
M.P. PÉREZ-PÉREZ ◽  
M.A. LUQUE ◽  
L. HERRERO ◽  
P.A. NÚÑEZ-ABADES ◽  
B. TORRES
Keyword(s):  
Reticular Formation ◽  
Optic Tectum ◽  
Mesencephalic Reticular Formation ◽  
Torus Semicircularis ◽  
Nucleus Isthmi ◽  
Posterior Commissure ◽  
Point Correspondence ◽  
Sensorimotor Transformations ◽  
Functional Zones ◽  
Point To Point

This work studies the afferent connectivity to different functionally identified tectal zones in goldfish. The sources of afferents contributed to different degrees to the functionally defined zones. The dorsocentral area of the telencephalon was connected mainly with the ipsilateral anteromedial tectal zone. At diencephalic levels, neurons were found in three different regions: preoptic, thalamic, and pretectal. Preoptic structures (suprachiasmatic and preoptic nuclei) projected mainly to the anteromedial tectal zone, whereas thalamic (ventral and dorsal) and pretectal (central, superficial, and posterior commissure) nuclei projected to all divisions of the tectum. In the mesencephalon, the mesencephalic reticular formation, torus longitudinalis, torus semicircularis, and nucleus isthmi were, in the anteroposterior axis, topographically connected with the tectum. In addition, neurons in the contralateral tectum projected to the injected zones in a symmetrical point-to-point correspondence. At rhombencephalic levels, the superior reticular formation was connected to all studied tectal zones, whereas medial and inferior reticular formations were connected with medial and posterior tectal zones. The present results support a different quantitative afferent connectivity to each tectal zone, possibly based on the sensorimotor transformations that the optic tectum carries out to generate orienting responses.

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