  We study one-loop effective action of Berkooz-Douglas Matrix theory and
obtain non-abelian action of D0-branes in the background field produced by
longitudinal 5-branes. Since these 5-branes do not have D0-brane charge and are
not present in BFSS Matrix theory, our analysis can be regarded as an
independent test for the coupling of D-branes to general weak backgrounds
proposed by Taylor and Van Raamsdonk, and also as a check of consistency
between the two versions of Matrix theory. The coupling to the 5-branes which
we obtain is basically consistent with the previous proposal, but we point out
subtleties in the ordering of matrices for the multipole moments.
