PRESENCE OF MOLECULES RELATED TO THE CHOLINERGIC SYSTEM IN PARAMECIUM-PRIMAURELIA (PROTISTA, CILIOPHORA) AND POSSIBLE ROLE IN MATING PAIR FORMATION - AN EXPERIMENTAL-STUDY

Cholinergic-like molecules were, for the first time, detected both in mating-competent and immature cells of Paramecium primaurelia. By hist ochemical and immunohistochemical methods, acetylcholinesterase activi ty was localized on the cell. surface of mating-competent cells and in the cytoplasm of immature cells. In mating-competent cells, molecules immunologically related to muscarinic acetylcholine (ACh) receptors w ere detected by immunofluorescence, and ACh nicotinic receptor-like mo lecules were revealed as a-bungarotoxin-binding sites. Aiming at verif ying whether cholinergic-like molecules were involved in mating pair f ormation, we incubated mating-competent cells in vivo with 10(-2) M AC hCl; with 10(-4) M carbamylcholine, and 10(-4) M atropine, agonist and antagonist of the muscarinic ACh receptors, respectively, as well as with 10(-7) M nicotine and 10(-7) M D-tubocurarine chloride, agonist a nd antagonist of the nicotinic receptors, respectively. After exposure to these cholinergic drugs, cell pairing was perturbed. The cell surf ace pattern of wheat germ agglutinine-affinity sites, which were prove d to be involved in pair formation, was enhanced in cells exposed to A ChCl and was depressed in atropine-treated cells. From these outcomes, a complete set of cholinergic-like molecules is shown, including both receptor classes, whose activation or inhibition somehow interferes i n Paramecium mating pair formation. (C) 1997 Wiley-Liss, Inc.