Changes in cell shape and induction of cell differentiation in the protozoan Herpetomonas samuelpessoai by cholinergic drugs.

Carbamylcholine, Pilocarpine and Atropine, but not Epinephrine, inhibited the motility of Herpetomonas samuelpessoai, when added to the suspension medium for 1 h. In addition, protozoan cells became spherical under the influence of atropine. This drug also induced the formation of the more differentiated opistomastigote form of the protozoan, in 60 per cent of growing cells, whereas these forms represented less than 5 per cent in untreated cultures. This may indicate that cholinergic receptors are present in this protozoan.