The Sensex at the Bombay Stock Exchange climbed 186 points, to regain the key 19,000 point mark, at 19,031, in opening trade, on sustained buying interest, amid firm regional bourses. But the Sensex later surrendered all its intital gains, on profit-booking, and stood 112 points, or 0.6 percent in negative territory, at 18,734, in afternoon deals, a short while ago. The 30-share Sensex had gained almost 1,300 points in the past six trading sessions. Other Asian markets in Japan, China, Indonesia, South Korea, Singapore and Taiwan were up by between 0.1 percent and 1.2 percent, today, on optimism that Greece will avoid a sovereign debt default. Wall Street's Dow Jones Industrial Average had surged 1.2 per cent, overnight.