Changes in the ultrastructure and function of goldfish Mauthner neurons in the presence of 3,4-dihydro-2(1H)-pyrimidinethione.

The behavioral effects of 3,4-dihydro-2(1H)-pyrimidinethione (DPT, a pyrimidine derivative), which is used as a test system for detecting tumor growth, on the ultrastructure and function of Mauthner neurons (MN), were studied in goldfish. Application of DPT to MN was found to lead to increased resistance of neurons to exhaustive stimulation, which was accompanied by increases in the sizes of actin-containing membrane desmosome-like contacts, along with the formation of bundles of actin stress fibers; these effects are similar to those previously reported with dopamine. The similarity of the morphofunctional changes in MN on exposure to an artificial chemical substance for which there are no membrane receptors and dopamine itself suggests that they have trophic effects on the stabilization and polymerization of cytoskeletal actin due to direct penetration into postsynaptic neurons.