EXTRINSIC CELLS, IMMUNOREACTIVE TO Ca-BINDING PROTEIN, AS SOURCES OF THALAMIC VISUAL
CENTRES IN TORTOISES
M. N. Minakova, N. B. Kenigfest, M. G. Belekhova
I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, RAS, St. Petersburg, Russia;
e-mail: belekhova@yahoo.com
Extrinsic sources of calcium-binding proteins involved in immunoreactive innervation of the visual thalamic nuclei
Rot and GLd in turtles (Testudo horsfieldi and Emys orbicularis) were studied using HRP tracing method and
immunohistochemistry. In 1.5-4.5 months after monocular enucleation calbindin (Calb)-, parval-bumin (Parv)- and calretinin
(Calr)-labeling was found in fragments of degenerated retinal fibers in the contralateral optic tract and in some retinorecipient
structures (optic tectum, GLd and GLv). Changes in GLd were detected in its neuropil part, in 2.0-3.5 months after unilateral
ablation of tectum and pretectum, the densities of Parv-, Calb- and Aclr-immunoreactivity terminals and fibers were diminisched in the
ipsilateral n. Rot, with the maximum effect seen in Parv. Following HRP injection into the visual thalamus (Rot and GLd), retrogradely
labeled cells with Parv label only, were revealed in the ventrothalamic nucleus Enta, pretectal nucleus Ptv, and in all types of
Ca-binding proteins (CaBPr) in separately labeled cells of the optic tectum. Thus, it has been shown that thalamic visual centers
in turtles have multiple extrinsic cells, which serve as sources of CaBPr projections. The present data suggest that organization of
CaBPr inputs to visual thalamus in reptiles (turtle) and higher am-niotes are fundamentally similar.
Key words: thalamic visual centers, reptiles, Ca-binding proteins, immunohistochemistry
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