A, velocity imbalance (VI) during VOR induction by rotation of the head at 0.1 and 1 Hz. Positive values represent velocity imbalance toward the injected side and negative values toward the contralateral side. B, gain of the VOR induced by rotation of the head at 0.1 and 1 Hz after injection of the different drugs. Gain is expressed as percentage of the control value for each experiment. Grey horizontal bar, 100 % ± s.d. of control values. C, changes in phase lead during the VOR induced by rotation of the head at 0.1 and 1 Hz produced by injection of the different drugs. Values are expressed in degrees (deg). Grey horizontal bar, 0 ± s.d. of control values. Values are expressed as means ± s.e.m. *P < 0.05 compared with control values, using the non-parametric Mann-Whitney U test. n = 5 for l-NAME; n = 3 for the other drugs.