NEW YORK—Financial markets reacted cautiously to the Senate’s passage of the banking bailout plan late Wednesday, with stock index futures falling and indicating a drop when trading resumes today. There was no discernible change in the credit markets after the vote.

Investors may be taking a wait-and-see approach until the House votes on the plan on Friday. But the caution may also be due to the fact that passage of the plan wouldn’t immediately erase the problems in the financial system, including credit markets that are currently stagnant.

Wednesday night, Dow Jones industrial average futures were down 85, or 0.78 percent, at 10,802. The Standard & Poor’s 500 index futures were down 9.8, or 0.84 percent, at 1,158.60, and Nasdaq 100 futures were down 17.75, or 1.1 percent, at 1,561.00.

In Japan, the Nikkei index was down 0.99 percent.

Caution was also apparent in Wednesday’s trading, which saw the Dow Jones industrials falling about 20 points after being down more than 200 earlier. The close was vastly different from the massive swings in the blue chips the first two sessions of the week.

Wall Street’s focus has been on credit markets that seem to be barely moving, and in turn, posing a threat to economic growth.

“We’ve taken the credit markets for granted much like you do the electricity coming on every day but in this particular case the power grid is down,” said Jim Dunigan, managing executive of investments at PNC Wealth Management. “If we don’t have a functioning credit market banks aren’t lending to each other—credit is dried up. That ultimately affects economic activity.”