Share prices ended the session almost unchanged, giving up morning gains, as investors began consolidating positions following a week of volatile trading action, dealers said. At the close of a session that was again shortened by half an hour due to exchange concerns about excess trades causing a system overload, the blue-chip Nikkei 225 stock ended up 0.41 points at 15,696.69. Yesterday, the benchmark gained 335.10 points or 2.3 pct to 15,696.28. On Tuesday and Wednesday however the main index shed nearly 1,000 points as investors dumped holdings on news of a probe into high profile Internet firm, Livedoor, for possible securities law breaches. The broader TOPIX index of all First Section shares closed slightly higher, gaining 4.10 points or 0.25 pct to 1,624.39. For the week, the Nikkei 225 index shed 4.6 pct while the TOPIX lost 3.4 pct. Losers led gainers 976 to 622, with 79 issues unchanged. Volume fell to 2.10 bln shares from 2.46 bln shares yesterday. The Tokyo Stock Exchange said earlier that the half-hour reduction in the afternoon session imposed on Thursday and today is likely to remain in effect next week. It said it will continue the shortened hours until trading levels return to more normal levels.