Origin of tectal cholinergic projections in amphibians: A combined study of choline acetyltransferase immunohistochemistry and retrograde transport of dextran amines

1999 ◽  
Vol 16 (2) ◽  
pp. 271-283 ◽  
Author(s):  
OSCAR MARÍN ◽  
AGUSTÍN GONZÁLEZ
Keyword(s):  
Choline Acetyltransferase ◽  
Functional Significance ◽  
Retrograde Transport ◽  
Cholinergic Innervation ◽  
Pedunculopontine Tegmental Nucleus ◽  
Laterodorsal Tegmental Nucleus ◽  
Tegmental Nucleus ◽  
Tegmental Nuclei ◽  
Pleurodeles Waltl ◽  
Cholinergic Projections

Immunohistochemistry for choline acetyltransferase (ChAT) revealed an extensive network of cholinergic fibers in the tectum of amphibians. The distribution of ChAT immunoreactive fibers was not restricted to superficial retinocipient layers, but also included deep tectal layers. The aim of the present study was to investigate the origin of the cholinergic inputs to the tectum of amphibians. For that purpose, application of retrograde tracers in the tectum of the anuran Rana perezi and the urodele Pleurodeles waltl was combined with ChAT immunohistochemistry. Double-labeled cells were found primarily in the nucleus isthmi of both species. The cholinergic isthmotectal projection is bilateral and topographically arranged and all retrogradely labeled cells found in this nucleus were ChAT immunoreactive. Remarkably, abundant cholinergic cells in two tegmental nuclei, the pedunculopontine tegmental nucleus (anurans) and the laterodorsal tegmental nucleus (anurans and urodeles), were demonstrated to provide additional cholinergic innervation to the tectum. We compare the present results with previously reported studies in amphibians and other vertebrates, and discuss the possible functional significance of the cholinergic innervation of the amphibian tectum.

Recovery of Cable Properties Through Active and Passive Modeling of Subthreshold Membrane Responses From Laterodorsal Tegmental Neurons

1998 ◽  
Vol 80 (5) ◽  
pp. 2593-2607 ◽  
Author(s):  
A. Surkis ◽  
C. S. Peskin ◽  
D. Tranchina ◽  
C. S. Leonard
Keyword(s):  
Experimental Data ◽  
Critical Role ◽  
Parameter Extraction ◽  
Pedunculopontine Tegmental Nucleus ◽  
Resting Potential ◽  
Cell Behavior ◽  
Laterodorsal Tegmental Nucleus ◽  
Tegmental Nucleus ◽  
Active Model ◽  
Cable Properties

Surkis, A., C. S. Peskin, D. Tranchina, and C. S. Leonard. Recovery of cable properties through active and passive modeling of subthreshold membrane responses from laterodorsal tegmental neurons. J. Neurophysiol. 80: 2593–2607, 1998. The laterodorsal tegmental nucleus (LDT) is located in the dorsolateral pontine reticular formation. Cholinergic neurons in the LDT and the adjacent pedunculopontine tegmental nucleus (PPT) are hypothesized to play a critical role in the generation of the electroencephalographic-desynchronized states of wakefulness and rapid eye movement sleep. A quantitative analysis of the cable properties of these cells was undertaken to provide a more detailed understanding of their integrative behavior. The data used in this analysis were the morphologies of intracellularly labeled guinea pig LDT neurons and the voltage responses of these cells to somatic current injection. Initial attempts to model the membrane behavior near resting potential and in the presence of tetrodotoxin (TTX, 1 μM) as purely passive produced fits that did not capture many features of the experimental data. Moreover, the recovered values of membrane conductance or intracellular resistivity were often very far from those reported for other neurons, suggesting that a passive description of cell behavior near rest was not adequate. An active membrane model that included a subthreshold A-type K+ current and/or a hyperpolarization-activated cation current (H-current) then was used to model cell behavior. The voltage traces calculated using this model were better able to reproduce the experimental data, and the cable parameters determined using this methodology were more consistent with those reported for other cells. Additionally, the use of the active model parameter extraction methodology eliminated a problem encountered with the passive model in which parameter sets with widely varying values, sometimes spanning an order of magnitude or more, would produce effectively indistinguishable fits to the data. The use of an active model to directly fit the experimentally measured voltage responses to both long and short current pulses is a novel approach that is of general utility.

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