Cholinergic and adrenergic nerve fibers in frog heart

Abstract

Objectives. 1. To map the cholinergic and adrenergic nerve fibers in frog atrial whole mounts. 2. To evaluate the fluorescence intensities and 2D areas of cholinergic and adrenergic nerve fibers in extended focus images of frog intracardiac nerves. 3. To check if our measured values differ in several regions of frog heart. Materials and methods. Common frogs, Rana temporaria, have been used for this study. Atrial whole mounts were prepared and stained immunohistochemically for choline acetyltransferase (ChAT) and tyrosine hydroxylase (TH). Extended focus images were obtained by confocal laser scanning and fluorescent microscopy. In fragments of extended focus images, we measured the following values: (1) fluorescence intensities of ChAT and TH positive fibers expressed as integrated densities in Image J software and (2) percentages of 2D areas occupied by ChAT and TH positive fibers. Results. Average integrated densities of ChAT and TH positive fibers did not differ significantly (Mean ± SE × 106 , 45.4 ± 7.6 vs. 33.9 ± 5.7; P = 0.268). Percentage of area occupied by ChAT positive and TH positive fibers also did not differ significantly (74.4 ± 2.7 vs. 80.7 ± 1.6; P = 0.123). Average ratio of integrated densities between ChAT positive and TH positive fibers was 1.38 ± 0.10). Average ratio of percentages of 2D areas occupied by ChAT positive and TH positive fibers was 0.93 ± 0.03. We did not find significant differences of investigated values within several cardiac regions examined. Conclusions. Our findings imply that both cholinergic and adrenergic fibers are distributed in major intracardiac nerves of frog. Proportional distribution of cholinergic and adrenergic fibers in frog intracardiac nerves is similar with respect to (1) amounts of neurochemicals ChAT and TH, and (2) areas the ChAT and TH positive fibers occupy. Our data contrasts to reports on mouse and rat heart where predominantly cholinergic or adrenergic nerves were reported.