Detection of cholinesterase activities and acetylcholine receptors during the developmental cycle of Dictyostelium discoideum Andrea Amaroli 1 , Lorenzo Gallus 2 , Mario Passalacqua 3 , Carla Falugi 2 , Aldo Viarengo 4 and Maria Umberta Delmonte Corrado 1, * 1 Department for the Study of the Territory and its Resources, University of Genoa, Corso Europa 26, I-16132 Genoa, Italy; E-mail: corrado@dipteris.unige.it 2 Department of Experimental, Environmental, and Applied Biology, University of Genoa, Viale Benedetto XV 5, I-16132 Genoa, Italy 3 Department of Experimental Medicine, Biochemistry Section, University of Genoa, Viale Benedetto XV 1, I-16132 Genoa, Italy 4 Department of Sciences and Advanced Technology, University of East Piedmont, Corso Borsalino 54, I-15100 Alessandria, Italy Received: 3 February 2003; 2 April 2003. Accepted: 4 April 2003 Previous results of our study carried out on Dictyostelium discoideum showed the presence in single-cell amoebae of both cholinesterase (ChE) activity, able to hydrolyze the propionyl thiocholine iodide sub- strate, and “true” acetylcholinesterase (AChE) activity, similar to that of Electrophorus electricus. These activities are sensitive to anti-ChE agents, and to the inhibitors classically used to discriminate different ChEs. In this work, we have investigated the presence of ChE activities and of both acetylcholine (ACh) nicotinic and muscarinic receptors, during the developmental cycle of D. discoideum. The spectrophoto- metric evaluation showed that slugs displayed the highest enzyme activities, AChE being the main activ- ity, while fruiting bodies exhibited the lowest. The presence of AChE activity was cytochemically detect- ed in all the cell populations of the developmental cycle, except in the fruiting bodies where it was local- ized exclusively to the level of the spores. Molecules recognized by the anti-butyrylcholinesterase anti- body were detected in single-cell amoebae, first fingers, slugs, and culminants, except in the fruiting bodies where they were found exclusively in the spore walls.The ACh nicotinic receptors were cytochem- ically identified in single-cell amoebae, slugs, and spores; however, molecules immunologically related to the ACh muscarinic receptors were not present in the spores. Key words: Cholinesterase activities; Acetylcholine receptors; Cell responses; Developmental cycle; Dictyostelium discoideum. trasynaptic regulatory processes, particularly in cell-cell interaction during fertilization, develop- ment, and differentiation (Drews 1975; Falugi and Prestipino 1987; Buznikov 1990; Falugi 1993; Bac- cetti et al. 1995). Actually, the signal molecule acetylcholine (ACh) was found to be widely ex- 0932-4739/03/39/02-213 $ 15.00/0 Introduction There is increasing experimental evidence that cholinergic molecules are not only specialized in- tercellular transmitters of nerve impulses, but that they can also play a multifunctional role in ex- *corresponding author Europ. J. Protistol. 39, 213–222 (2003) © Urban & Fischer Verlag http://www.urbanfischer.de/journals/ejp