The Sensex gained over 134 points in opening trade today on the back of buying by funds and retail investors in stocks of oil and gas, realty and banking companies amid a firming trend on other Asian bourses. The 30-share barometer, which lost 115 points in Thursday's trade, rebounded by 134 points to 18,628 points in the first few minutes of trade today. In a similar manner, the wide-based National Stock Exchange Nifty index moved up 42 points to 5,592 points.