Abstract
Catecholaminergic neuronal structures were investigated in the rotifers Brachionus plicatilis, Asplanchna priodonta and Asplanchna herricki, using three different aqucous histofluorescent methods. The adrenergic receptors were labelled using the dansyl analog of propranolol, a beta-adrenergic blocker. Catecholamine neurotransmitters were visualized by derivatizing with glyoxylic acid and formaldehyde respectively. Although all three methods lead to similar results, dansylpropranolol gave the most rapid and strong fluorescence. The results reveal a complex and highly developed catecholaminergic neuronal system in all adult organs and sensory structures. While developed embryos in the egg show strong fluorescence, immature eggs do not.