The move provides the offensively challenged Predators a much-needed scoring threat in Neal. The Penguins, meanwhile, gain some depth on the wing with Hornqvist and Spaling.
"In this deal, we got to drop our cap a little bit with Hornqvist," Penguins general manager Jim Rutherford said. "We like Hornqvist as an all-around player. Hornqvist plays at the net, goes to the net, works the corners. We like his all-around play."
Hornqvist, 27, had 22 goals and 31 assists in 76 games this season, which marked the fourth time in his career he reached the 20-goal mark. He has 106 goals and 110 assists in 363 career regular-season games, all with Nashville. Hornqvist's best season came in 2009-10, when he scored a career-high 30 goals.
Spaling, 25, had 13 goals and 19 assists in 71 games for Nashville this season. He has 40 goals and 44 assists in 207 career regular-season games.
"We like Spalding, he can play all three positions on the third line," Rutherford said. "I think we were just trying to change the mix of our team a little bit and get a little different type player."
Though Neal is coming off a disappointing playoff performance, he recorded 27 goals and 61 points in 59 games during the regular season. The 26-year-old winger, who is entering the third year of a six-year, $30 million contract, is only two seasons removed from a career-high 40-goal season for the Penguins in 2011-12.
Neal had been with the Penguins since 2010 after beginning his career with the Dallas Stars.
Several reports indicated a flurry of activity around Predators general manager David Poile on the draft floor, presumably leading up to the trade. But while Poile acquired a proven goal scorer to bolster an anemic offense that ranked 19th in the league this past season, Neal has his fair share of critics that will point out that he has not performed nearly as well without the likes of superstar Evgeni Malkin on his line.
Friday's deal also marked the first significant trade by newly hired Rutherford, who is entering his first offseason as general manager of the Penguins.
Earlier in the day, top center Ryan Kesler was traded from the Vancouver Canucks to the Anaheim Ducks for two players and a draft pick. The NHL and NHL Players' Association also announced a lower-than-expected salary cap limit of $69 million for 2014-15.
Whether that figure sparks more activity on the draft floor remains to be seen. Round 1 of the draft will be completed Friday night, with Rounds 2 through 7 set for Saturday.
Information from The Associated Press was used in this report.