Rats show unimpaired learning within minutes after recovery from single bolus propofol anesthesia

Purpose: To examine the learning ability of rats shortly after recovery from a bolus dose of propofol by assessing learning on a swim-to-platform task. Also, muscarinic blockade was used as a pharmacological test of whether learning shortly after propofol anesthesia resembles normal learning. Methods: Propofol anesthetized rats (15-20 mg · kg^-1 iv) were trained on a swim-to-platform task five to seven minutes after recovering from surgical anesthesia and tested two to three hours later. In addition, the muscarinic antagonist scopolamine hydrobromide (5 mg · kg^-1 sc) was given to a subgroup of rats before testing. During 10 trials, the number of times a given rat took 10 sec or longer to locate and climb onto a visible platform was tabulated and counted as errors. Results: When trained shortly after recovery from the anesthetic, propofol anesthetized rats made 3.2 ± 0.4 compared with 1.0 ± 0.1 errors in controls (P < 0.0001). Two to three hours later both groups performed equally well. Rats trained after propofol anesthesia and given scopolamine before testing made 0.7 ± 0.5 errors and performed as well as normal controls, 1.2 ± 0.2 errors when subjected to the same procedures without propofol anesthesia, and better than scopolamine- treated untrained rats 5.5 ± 0.7 errors, (P < 0.05). Conclusion: Training five to seven minutes after recovery from propofol anesthesia resulted in normal retention of the swim-to-platform task. It also produced the same resistance to the disruptive effects of scopolamine as did training in rats that were not anesthetized. Thus, the ability to learn recovers rapidly after propofol anesthesia induced by a single intravenous bolus dose.