Аннотация:In 1989 an observational program of searching for chemically decoupled nuclei in nearby galaxies was started. For this purpose the Multi-Pupil Field Spectrograph of the 6m telescope (Special Astrophysical Observatory RAS, Nizhnij Arkhyz, Russia) was used. Bidimensional spectroscopy allows to obtain radial profiles of absorption-line strengths, surface brightness maps and two-dimensional velocity fields during one exposure. During the period of 1989-1996 magnesium-line strength breaks between nuclei and the nearest bulge regions have been found in 10 early-type spiral galaxies and in 8 lenticulars. The presence of chemically decoupled nuclei appears to be related to the presence of dynamically decoupled subsystems in galaxies. In particular, chemically decoupled unresolved nuclei are found in NGC 7331, where a part of the bulge counterrotates, and in NGC 4826, which is known by a counterrotating global gaseous disk at R > 1 kpc. A detailed kynematic investigation of a regular Sb galaxy NGC 2841, which also possesses a chemically decoupled nucleus, has shown that the nuclear ionized gas in this galaxy rotates perpendicularly to the rotation plane of the nuclear stellar population, and there may be a radially limited zone of the stellar bulge (R = 5"-12") which matches the rotation of the nuclear gas. After that it seems quite natural that chemically decoupled nuclei are also found in "bona fide" polar-ring galaxies NGC 2685 and IC 1689. Perhaps now we can state that an origin of chemically decoupled nuclei is related to some gas accretion event or a gas-rich dwarf merging followed by a secondary star-formation burst in the galactic centers.