Olfactory conditioning impairment following posttraining NMDA receptor blockade in neonatal rats.
Six-day-old Sprague-Dawley rat pups were exposed to peppermint odor paired with tactile stimulation (stroking the skin with a paint brush) for twenty 10-s conditioning trials, and their olfactory preference was tested the next day. In Experiment 1, pups that had received an injection of the noncompetitive N-methyl-D-aspartate receptor antagonist MK-801 (0.1 mg/kg, i.p.) either 30 min before or immediately after conditioning spent less time over the conditioned odor than saline-treated controls. In Experiment 2, pups received an injection of either MK-801 or saline 0, 30, or 60 min after the training period. There was a reduction in the preference for the conditioned odor in the animals receiving MK-801 immediately following training, but treatment with the drug at the other intervals did not produce a performance impairment. The impairment following immediate posttraining injection occurred with either 0.05 or 0.1, but not with 0.01 mg/kg of MK-801 (Experiment 3). Experiment 4 provided control data to confirm that pups that had experienced the procedures used in Experiments 1-3 showed greater preference for the conditioned odor than did naive pups or those receiving exposure to the odor without stroking. The data indicate that immediate posttraining activation of N-methyl-D-aspartate receptors is required for normal olfactory learning in neonatal rats.
Weldon
D A
DA
Hamilton College, Clinton, New York 13323, USA.
Fedorcik
G G
GG
LoRusso
C M
CM
Tiburzi
M J
MJ
Lenoci
J M
JM
D000818:Animals; D000831:Animals, Newborn; D001522:Behavior, Animal; D003213:Conditioning, Psychological; D016291:Dizocilpine Maleate / Q000494:pharmacology*; D005260:Female; D007858:Learning / Q000187:drug effects; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*; D012903:Smell / Q000187:drug effects*; D014110:Touch
D016194:Receptors, N-Methyl-D-Aspartate; D016291:Dizocilpine Maleate