Pharmacologically increasing or decreasing endogenous GABA levels in the pontine reticular nucleus, oral part (PnO) altered propofol induction time but not recovery time. Administration of 3-mercaptopropionic acid (3-MPA) and nipecotic acid (NPA) into the PnO significantly decreased (A) or increased (B), respectively, the time to Loss of Righting Response (LoRR). In contrast, 3-MPA (C) and NPA (D) had no effect on the time to Resumption of Righting Response (RoRR) after propofol anesthesia. Relative to wakefulness, extracellular GABA levels in the PnO were significantly decreased (E and F) during anesthesia with propofol.