CINCINNATI - For the first time in five weeks, the Houston Astros have to worry about catching up instead of fending off.

Adam Dunn's two-run homer in the 10th inning Friday night gave the Cincinnati Reds a 9-7 victory and left the Astros a half-game out of first place. They'd stayed in the top spot since July 7 by avoiding a slump.

After blowing a late lead against a struggling team, the Astros have lost four in a row, matching their season high. They're tied for second with St. Louis, a half-game behind the Chicago Cubs.

''Everybody goes through this situation, and we're in it right now,'' said reliever Octavio Dotel, who allowed the Reds to rally for five runs in the seventh. ''I hope it changes.''

Houston can't seem to get in sync lately. A slumping offense finally came around, but a usually dependable bullpen gave up more runs in one night than it had in the last eight games.

''We're having a few rough days,'' said starter Ron Villone, who hit his first career homer and turned a 3-2 lead over to the bullpen. ''We've got to get over them. We'll be all right.''

A day after they ended a 16-game losing streak against Arizona, the Reds broke a 10-game skid against the Astros by getting yet another game-ending hit.

D'Angelo Jimenez led off the 10th with a single off Brad Lidge (4-3). One out later, Dunn hit an up-and-in fastball for his 27th homer, his first RBI since July 30.

''That's a pitch they've been getting me out on for the last couple of years,'' said Dunn, who has produced 43 of his 57 RBIs off homers. ''I'm either a little too early or a little too late, and I pop it up.''

Not if the game's in extra innings. That's the only time when the Reds are consistently at their best.

It was the Reds' 13th game-ending hit of the season and their 27th win in their last at-bat, most in the majors. Fourteen of their 54 wins have come in extra innings.

Ryan Wagner (2-0) pitched the 10th to get his second career victory in a game that was low-scoring through six innings, then wild at the end.

Jeff Kent hit a two-run homer in the first off Danny Graves, but Jason LaRue matched it with a two-run shot off Villone in the bottom of the inning.

It stayed tied until the seventh, when Villone led off with his first career homer. The left-hander swung from his heels on a 1-1 pitch, sending the ball well back into the seats in right field for a 3-2 lead.

''I'm up there just swinging,'' said Villone, who homered in his 152nd career at-bat. ''I got lucky and ran into it. I'd trade it for a win, though.''

The milestone homer put Villone in line to improve to 6-0 career against his former team, but Dotel couldn't hold the lead. He loaded the bases with a walk in the bottom of the seventh, then gave up a two-run double to Ray Olmedo and a two-run single by LaRue. Jimenez's RBI single made it 7-3.

The Reds bullpen then had a meltdown of its own, depriving Graves of his first victory since July 1. John Riedling gave up a sacrifice fly to Geoff Blum for the second out in the eighth, and Craig Biggio followed with his third hit of the game, a three-run homer that tied it at 7.

Notes: Packs of 2003 Reds baseball cards were handed out as part of a promotion. The packs included manager Bob Boone, who was fired on July 28, two of his fired coaches and five players who were later traded. … Reds SS Barry Larkin will sit out the three-game series. He hasn't played since Tuesday, when he aggravated scar tissue from a hernia operation in 2001. … Olmedo's throwing error at SS was the Reds' 111th in 121 games, the most in the majors.