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 to 16995.13.
The broad-based S&P 500 added a scant 0.31 points at 1 989.57, while the tech-rich Nasdaq Composite Index fell 12.22 points 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," Esiner said.
DuPont was the biggest loser in the Dow, falling 2.0%. The biggest gains came from Chevron, up 1.2%, and Intel, up 1.3%.
Dollar General climbed 10.7% as fourth-quarter net income rose 5.9% to $376m and the discount retailer announced plans for $1bn in share repurchases in 2016.
Digital payments company Square fell 6.1% as it reported a 47% jump in gross payment volumes in the fourth quarter, but also a 52% rise in operating expenses to $157m. 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% 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.