An Arlington patent attorney who was "one of the major targets of the investigation" into bribery and corruption at the U.S. Patent Office in Arlington, yesterday pleaded guilty to one charge of bribery in U.S. District Court in Alexandria.

Anthony J. Castorina, 43, yesterday became the 11th person to plead guilty to charges in connection with bribery of patent office employes, according to Assistant U.S. Attorney Theodore S. Greenberg.

Castorina, of 2909 N. Nottingham St., Arlington, was indicted on 10 counts of bribery and one count of attempting to influence a grand jury witness. All but one bribery charge was dropped as part of a plea agreement.

Patent searchers, patent attorneys and hundreds of inventors search patent office files every year to make certain that an idea is not already patented. They usually pay 50 cents for a coupon that entitles them to have the patent they are interested in searched and copied by patent employes, a process that takes about three weeks, Greenberg said.

Castorina was accused of giving four patent employes an average of $20 to $40 a week to get patent copies for him in advance of the usual three-week waiting time. The incidents occurred with each of the employes for periods of time up to seven years and involved between 20 and 25 patents per employe each week, according to court papers.

Castorina also was accused of paying another employe between $10 and $15 a week to sell him unused coupons at a discount, Greenberg said.

According to court papers, Castorina's legitimate purchases of patent office coupons dropped from $2,115 in $973 to $55 in 1975. He faces a possible penalty of up to two years in prison and a $10,000 fine. He is scheduled to be sentenced on July 10.

Seven others have pleaded guilty to misdemeanors and three others have pleaded to felonies as a result of the investigation.