Montgomery County Executive Neal Potter announced yesterday that the county has received a $2.5 million federal grant to pay for neighborhood-based drug and alcohol abuse programs.

Potter said the grant, one of the largest of its kind, will finance programs in the Longbranch area of Silver Spring, the Wheaton and Kensington communities, and the Emory Grove area of Gaithersburg -- areas where drug arrests are on the increase.

The focus of the efforts will be on prevention, and Potter said the programs will be designed by the civic, church and business groups of those areas.

"Communities are the strength and life of Montgomery County," Potter said, adding that it will be up to the people in the areas to decide what will work and what won't.

County Council member Derick Berlage (D-Silver Spring) said, "There is a secret weapon against the problem of drugs . . . good, old-fashioned community action."

Potter noted that it was appropriate he was making one of his first public appearances as executive to announce the new drug programs, saying that the problems of drug addiction and abuse will be among the top priorities of his administration. Potter has said that his experience with his grandson -- who had a problem with drugs -- has made him more sensitive to the issue.

Potter chose the center court of Wheaton Plaza, bustling with holiday shoppers, for his announcement. One of the shoppers who passed by was former county executive Sidney Kramer, the man Potter defeated in the Democratic primary.

Potter said a new Montgomery County Prevention Center will open in 1991 to serve as a clearinghouse for information. The county already has such a center, in Rockville, but Potter said he wants it expanded to include an educational theater. He said the location has yet to be decided, but the center will remain in the Rockville area.

The federal grant is for five-year demonstration projects. County officials said the grant will include recruiting volunteers, determining the particular needs of each neighborhood, developing and implementing prevention programs and evaluating the effectiveness of the programs.