Fig. 3. Effect of racemic ketamine ( A ) and S (+)-ketamine ( B ) on the time course of force of contraction (FoC) of isolated human right atrial trabeculae during a 30-min hypoxic challenge followed by a 60-min reoxygenation period. Fifteen minutes of exposure to ketamine and S (+)-ketamine (10−6m [ S (+) Keta-6], 10−5m [ S (+) Keta-5], and 10−4m [ S (+)Keta;-4]; n = 6 in each group) was followed by a 10-min washout period before the 30-min hypoxic challenge. Data are presented as mean ± SD. NS = not significant.