CBS Corp., the TV and radio broadcaster battling shrinking advertising sales, chopped its dividend 81 percent and reported fourth-quarter profit tumbled as marketers continued to cut spending.

The quarterly payout was reduced to 5 cents a share from 27 cents, CBS, the broadcaster controlled by Sumner Redstone, said in a statement.

CBS faced a possible loss of its investment-grade credit rating after Standard & Poor’s said the payout should be cut in a climate of falling ad sales.

Dividends have been a cornerstone of CBS’s strategy since Redstone, the chairman and controlling shareholder, split the company from Viacom Inc. three years ago.

The company reported net income fell 52 percent to $136.1 million, or 20 cents a share, from $286.2 million, or 42 cents a share, a year earlier.

CBS shares, which have lost 80 percent of their value in the past 12 months, gained 43 cents to $5.56 in after-market trading. They fell 12 cents to $5.13 in regular NYSE trading.

Sales dropped 6.2 percent to $3.53 billion, compared with the $3.57 billion average of analysts’ estimates.