The BSE benchmark Sensex opened 145 points lower today after investors' confidence was shaken by yesterday's serial bomb blasts in the country's financial capital, amid a weakening overseas trend. The 30-share barometer, which had gained 184 points in the previous session, fell by 142 points, or 0.78 per cent, to 18,451 in the first five minutes of trade.In a similar fashion, the wide-based National Stock Exchange Nifty index declined by 37 points, or 0.66 per cent, to 5,548.In the Asian region, Hong Kong's Hang Seng index was trading 0.23 per cent lower and Japan's Nikkei shed 0.34 per cent this morning.