[NEW YORK] The Dow and Nasdaq finished slightly lower on Thursday following a topsy-turvy session after the European Central Bank unveiled a series of aggressive stimulus measures.
The Dow Jones Industrial Average dipped 5.23 points (0.03 per cent) to 16,995.13.
The broad-based S&P 500 added a scant 0.31 (0.02 per cent) at 1,989.57, while the tech-rich Nasdaq Composite Index fell 12.22 (0.27 per cent) to 4,661.16.
Movements in US markets were broadly parallel to those in Europe, where stocks initially surged on ECB moves to cut interest rates and boost bond-buying. However, stocks fell sharply after ECB Chief Mario Draghi said the bank did not anticipate further interest rate cuts.
US stocks managed to fight back to almost flat after the Dow was down nearly 180 points at one point.
"It's a wild day," said Omer Esiner, chief market analyst at Commonwealth Foreign Exchange.
The stimulus package exceeded the market's expectations, but Draghi's comment on future rate cuts "signals the policy hawks within the ECB continue to wield significant power among the decisions of the central bank," Mr Esiner said.
DuPont was the biggest loser in the Dow, falling 2.0 per cent. The biggest gains came from Chevron, up 1.2 per cent, and Intel, up 1.3 per cent.
Dollar General climbed 10.7 per cent as fourth-quarter net income rose 5.9 per cent to US$376 million and the discount retailer announced plans for US$1 billion in share repurchases in 2016.
Digital payments company Square fell 6.1 per cent as it reported a 47 per cent jump in gross payment volumes in the fourth quarter, but also a 52 per cent rise in operating expenses to US$157 million.
Deutsche Bank said the company had made a "solid start" in its first full quarter as a public company.
Cloud computing company J2G Global slumped 19.9 per cent following a report from short-selling firm Citron Research that said the company's growth prospects were poor and that shares are due for a big pullback.