Bidding for a first win in the event since 2012, the Scots held the upper hand in the morning foursomes until Lewis Irvine and Stuart Easton lost the last three holes in their match.
That left Ireland leading 3-2 and they never really looked like relinquishing their advantage in the afternoon singles session.
Scotland captain Matthew Clark, who is making his ninth consecutive appearance in the event, recorded a 6&5 win over T.J.Ford while debutant Andrew Ni beat Hugh Foley 7&6.
Easton and Rory Franssen also delivered victories over Peter O’Keefe and Jack McDonnell respectively, while 2019 Scottish Amateur champion George Burns fought back against Matt McClean to add a half point in the bottom match.
But Ireland came out on top in the other five games, with both Irvine and current Scottish champion Angus Carrick losing on the last green.
Earlier, Carrick and Connor Wilson had suffered a heavy defeat in the opening foursomes match before Clark and Darren Howie joined forces to win for the Scots along with Ni and Burns.
Murrayfield man Ni’s double success on the opening day vindicated his decision to travel nearly 5,000 miles to make his debut, having been back at college in Colorado when he was selected.
Scotland now take on defending champions England, who beat Wales 10.5-4.5 in the other match.
Laird Shepherd, the St Andrews-based Amateur champion, won both his games for England, add a 3&2 singles success over Tim Harry to a morning victory alongside Zachary Chegwidden.
Overall, England has won or shared the title on 46 occasions, Scotland 26 times, Ireland 18 with Wales lifting the trophy on one occasion.
In the pro ranks, Craigielaw’s Gabrielle Macdonald made a promising start in the Lavaux Ladies Open on the LET Access Series
Macdonald, a first-time winner on the circuit earlier in the year, opened with a three-under-par 69 to sit two shots off the lead in joint-fifth. Rachael Taylor is also in the top 15 after starting with a 70.