Effect of a nonsedative dose of propofol on memory for aversively loaded information in rats.
BACKGROUND
The effects of propofol on memory for aversive information are not well determined. The authors evaluated the effects of a minimal nonsedative dose of propofol or midazolam on memory in rats, using an apparatus composed of two compartments: a large bright anxiogenic one and a small dark neutral one.


METHODS
Groups of rat received propofol (9 mg/kg, intraperitoneally) or midazolam (3 mg/kg). Anxiety was assessed in rats placed in the anxiogenic compartment as the time before the animals entered the neutral compartment. Memory for an aversive event was assessed in rats placed in the anxiogenic compartment as the time to enter the neutral one where they previously experienced foot shocks (fear conditioning). To assess the memory for a nonaversive event, rats were placed in the neutral compartment with no shocks (preexposure). The following day, rats were placed in it and they experienced foot shocks. As a result of the preexposure, rats exhibit less fear to enter it.


RESULTS
Propofol and midazolam increased the time to enter the neutral compartment. Propofol or midazolam was given to rats before experiencing foot shocks in the neutral compartment. When later tested, the time to enter it was decreased. Propofol or midazolam was given to rats before the preexposure to the neutral compartment. When later tested, the latency to enter it was not modified by the preexposure.


CONCLUSIONS
Propofol and midazolam impaired memory for aversive and for nonaversive experiences at equianxiolytic doses that do not produce locomotor impairment in rats.
Pain
Laure
L
Groupe de Recherche Experimentale sur les Répercussions Cognitives de l'anesthésie (GRERCA) and Laboratoire de Psychopathologie et Pharmacologie de la Cognition (U405 INSERM), Strasbourg, France. Laurepain@aol.com
Angst
Marie-Josée
MJ
LeGourrier
Laurence
L
Oberling
Philippe
P
D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D000818:Animals; D004924:Escape Reaction / Q000187:drug effects*; D007274:Injections, Intraperitoneal; D008124:Locomotion / Q000187:drug effects; D008297:Male; D008568:Memory / Q000187:drug effects*; D008874:Midazolam / Q000494:pharmacology*; D015742:Propofol / Q000494:pharmacology*; D051381:Rats; D020318:Rats, Long-Evans
D018686:Anesthetics, Intravenous; D008874:Midazolam; D015742:Propofol