Histofluorescent Study of Catecholamine-Containing Elements in Cholinergic Ganglia from the Calf and Dog Lung

Abstract

An extensive system of varicose adrenergic nerve terminals has been found in close proximity to sympathetic ganglion cells (1-4). Furthermore, intraganglionic adrenergic-like nerve terminals are present in some parasympathetic visceral ganglia, most notably those in cholinergic ganglia of the digestive tract (5-7) and heart (8). The present study represents a histofluorescent examination of catecholamine-containing elements in cholinergic ganglia from calf and dog lung. Calf lung cholinergic ganglia were found to contain varicose adrenergic fibers; analogous ganglia in dog lung were devoid of such elements.

Materials and Methods. Two calves and two dogs were anesthetized with 35 mg/kg sodium pentobarbital. Tissues from the hilar regions of the lungs were rapidly removed and immediately frozen in isopentane cooled by liquid nitrogen. Specimens were freeze dried in vacuo at — 35° for 3 to 7 days and then treated with paraformaldehyde gas at 80° for 1 hr according to the method of Falck and Hillarp (9, 10). Paraffin sections were cut at 14 μm and examined for monoamine fluorescence with a Leitz fluorescence microscope. Photographs were taken using Kodak Tri K film.

Results. Clusters of cholinergic ganglion cells were readily identified in connective tissue regions lateral to the cartilage rings of the intrapulmonary bronchi. The cholinergic nature of these ganglia was apparent from their low background fluorescence, occasionally augmented by orange-yellow autofluorescent lipofuscin pigment granules in some of the cell bodies (8). Ganglia of the calf lung contained green fluorescent varicose fibers in proximity to some of the cell bodies (Fig. 1). About 10% of the cell bodies appeared to be in apposition to adrenergic-like fibers. Large green fluorescent smooth nerve trunks occasionally penetrated the ganglia. Also, many intense green fluorescent mast cells were observed in the lung; a small number of mast cells were seen within the ganglia.