Adriano Panatta gave his adoring hometown fans an emotional ride from the ridiculous to the sublime yesterday, reviving himself from 0-5 in the first set and 3-5 in the second to dethrone Italian Open champion Vitas Gerulaitis, 7-6, 7-5, in a first-round match that seemed more like a final.

It was not a great match, but was fascinating and exciting: a quintessential Roman tennis experience, complete with raucous crowd participation and a couple of critical close calls made in Panatta's favor by officials with Italian hearts. They helped their national idol through a torturous tied breaker, and his shotmaking and the inspiration of the crowd got him home from there.

A packed house of more than 7,000 in the white marbel echo chamber that is Foro Italico despaired with Panatta through five pitiful games, then soared as he rediscovered the fluid strokes that made him the premier champion of both Italy and France.

Their applause, cheers and rhythmic chants swelled as the noblest tennis-playing Roman of them all saved the suddenly dazed and erring Gerulaitis, passing him repeatedly with searing backhands down the line.

Ultimately, Gerulaitis - the extrovert New Yorker who captivated the Italians by surging unexpectedly to a year ago - was not up to battling the crowd and the umpire as well as the rejuvenated Panatta.

The turning point came in a dramatic tie breaker won by Panatta, 7 points to 4, with the help of desperate lunging volley, those two questioning shots he recalled from days of fonder memories.

A year ago, Panatta was the defending camp, seeded first in this second most important clay court event on the continent. This year he was unseeded, having slipped from the world top 10 in 1976 to no. 38 in the latest computer ranking of the Association of Tennis Professionals.

Last week in Florence, he was humiliated by Rick Fagel, ranked only 39th in the United States. He seemed to have lost completely the fluid strokes, graceful aggression, and oppressive serve-and-volley rhythm tempered with touch of two seasons ago.

Gerulaitis beat panatta in the quarterfinals last year, and although he had only two days to adjust to slow ared clay and heavy, pressureless balls, having arrived Saturday on leave from the New York Apples fo World Team Tennis, he was expected to win. His confidence was running high after his $100,000 victory in the World Championship Tennis finals at Dallas a week ago Sunday.

Both players were given thunderous ovations by the sell-out crowd lured on a cool and sunless afternoon by the tantalizing prospect of the flamboyant 23-year-old champion against the dashing 27-year-old former champ in the first-round.

But the noisy enthusiasm waned as Panatta won only four points in the first five games, losing 12 in a row at one stage. He was worse then bad . . . absolutely pathetic as he overhit easy forehands, awkwardly steered volleys with a flaccid wrist, and showed no feel for the ball or control over his shots.

At 0-5 he was whistled and hooted. He showed his aggravation by frowning and gesturing to the crowd, as if to say, "Give me a break . . . you are putting to much pressure on me." Passionate vocal support returned when he finally held serve for 1-5, and he became a different player thereafter.

Greatly helped by a simultaneous collapse by Gervlains, who looked as if he needed ear plugs, Panatta clawed back to 5-5, saving two set points from 15-40 in the eighth game with three good volleys.

Gerulaitis, annoyed by losing a point on what he thought had been a "let" serve and another that was called a "let" when he didn't think it was, held for 6-5, after saving a break point with his second second-serve ace. He threw down a ball defiantly, and derisive chants cascaded down on him.

Panatta held to send the set into a tie breaker, and at 1-1, Panatta drove for a backhand volley and nicked it off the frame of his racket for a winner while stretched horizontally. He landed with a thud, red sust caking his white shirt and shorts, and the stadium shook with an appreciative roar.

Two points later, Gerulaitis apparently went ahead 3 points to with a first volley winner, but again a "let" was called. Gerulaitis couldn't believe it, swuawked angrily at the umpire who made the call (here was not net judge), then lost the replayed point. Panatta, expanding in confidence, took advantage of his opponents mounting frustration.

Panatta lost his serve in the first game of the second set, but broke right back to 1-1. He lost his serve again on a double fault in the seventh game and trailed 3-5. But when Gerulaitis served for the set Panatta broke him at 30 with three exquisite backhand sown-the-line passes.

Panatta continued to serve poorly, but had regained his old panache and confidence in his passing shots and volleys. Instead of the recent tame Kitty, he began to look like the sleek cat of 1976, springing like a puma to put away piercing volleys, stretching his lithe and powerful 6-foot-2 frame to angle away magnificent bachhead smashes.

Gerulaitis, normally a sure volleyer, began missing easy ones, and pushing his serve. His concentration has been eroded by the constant aggravation, and the partisan din that fueled Panatta's resurrection.

After 1 hour 42 minutes, when Panatta punched home his final forehand cross-court volley on the second match point, Gerulaitis quickly shook hands and stormed off, angry and depressed.

It was an abrupt end to his reign as champion, and he felt lonely in the arena where he had triumphed as syectacularyly a year ago.