A, RPA with a probe for Kv3.1b. Lane 1, probe. Lane 2, negative control (tRNA). Lanes 3 and 4, RNA from one dog atrium in each lane (DA1, DA2). Lane 5, RNA extracted from isolated canine atrial myocytes (DA3). Lane 6, RNA from rat brain (RB). B, RPA with a probe for Kv3.1a and Kv3.1b. Lane 1, probe. Lane 2, tRNA. Lane 3, RNA from dog atrium. Lane 4, rat brain sample.