text: Moreover, 4-methylhistamine potently activated the hH(4)R (pEC(50) = 7.4 +/- 0.1; alpha = 1), and this response was competitively antagonized by the selective << H(4)R >> antagonist JNJ 7777120 [[[ 1-[(5-chloro-1H-indol-2-yl)-carbonyl]-4-methylpiperazine ]]] (pA(2) = 7.8).