Spectral profiles of the maser emission from the metastable NH₃ (6, 6), (7, 7), (9, 9) inversion transition lines observed toward W51-North with the JVLA B-array. The radial velocities are derived with respect to the LSR. The vertical dashed line indicates a velocity of 47.6 km s^-1. The velocity resolution is 0.4 km s^-1. We note that different flux density scales are adopted for different transitions. We also note that the two ortho transitions, the (6, 6) and (9, 9) lines, show similar profiles, whereas the only para transition, the (7, 7), shows a double-peaked profile (see text).