North were the visitors at Bathgate, where the three morning foursome matches all went the distance as the session ended 1.5-1.5.
The afternoon singles were also keenly-contested, with two of the games going to the 18th and another being decided on the 17th.
In the end, Lothians won the session 4.5-1.5 to record a 6-3 success.
Lothains face Borders away at Torwoodlee in the final group matches in July and, with one team from each section progressing to the finals weekend at Powfoot in September, two more strong performances will be required.
Last year Lothians landed a record 14th title triumph but a first under a changed format.