Soviet authorities have seized a Kharkov psychiatrist who helped defend dissidents incarcerated in Soviet mental hospital because of their political views, unofficial sources reported.

Dr. Anatoli Koryagin, 42, was arrested Feb. 13 on a train from Kharkov to Moscow, Washington Post correspondent Kevin Klose quoted dissidents as saying. In mid-January, Koryagin met two Western correspondents in Kharkov to discuss his work for the unofficial Commission for the Investigation of the Use of Psychiatry for Political Purposes in the Soviet Union, virtually all of whose members have been jailed in the past year.

During those interviews, he reiterated an earlier written statement that mining engineer Alexei Nikitin, who was send to a Dniepropetrovsk mental hospital after talking with correspondents, was "totally healthy."

Dissidents said Koryagin's arrest may be linked to the fact that he had openly questioned the confinement to mental hospitals of Nikitin, who already had spent seven of the past 10 years undergoing forced psychiatric treatment and imprisonment. Nikitin was expelled from the Communist Party in 1969 and fired from his job at the Butovka mine in 1970 after protesting work and safety conditions.

Meanwhile, it was learned that Vasili Baratz, another dissident activist, was seized yesterday and taken to a Moscow mental hospital for unspecified reasons. Baratz, a former Red Army officer and computer specialist, is a member of an unofficial social group concerned with the right to emigrate.