Hippocampal NMDA receptors are necessary for auditory trace fear conditioning measured with conditioned hypoalgesia in rats.
We tested whether N-methyl-D-aspartate (NMDA) receptors in the dorsal hippocampus (DH) are critical for the acquisition of trace fear conditioning using conditioned hypoalgesia (CHA), decrease in pain reactivity, as the conditioned response (CR) instead of commonly used freezing. Infusions of the NMDA receptor antagonist, DL-2-amino-5-phosphonovaleric acid (APV) into DH prior to conditioning resulted in impaired CHA, measured with the radiant heat tail flick test, only in the trace-conditioning group when they were tested during the trace interval. The same infusion had no effect on CHA in the delay-conditioned animals. The results support that NMDA receptors in DH are critically involved in associating the CS with the US across a temporal gap. In addition, temporal specificity of the CR was revealed as CHA was induced only in the temporal vicinity of the US used for the training.
Department of Psychology, Korea University, 5-1 Anam-Dong, Seongbuk-Gu, Seoul, 136-701, Republic of Korea.
Dong-Oh
DO
Seo
Min-Hee
MH
Pang
Maeng-Sik
MS
Shin
Hyun-Taek
HT
Kim
June-Seek
JS
Choi
D015763:2-Amino-5-phosphonovalerate / Q000008:administration & dosage / Q000633:toxicity; D000161:Acoustic Stimulation / Q000379:methods; D000818:Animals; D001245:Association Learning / Q000187:drug effects / Q000502:physiology; D001522:Behavior, Animal; D001930:Brain Injuries / Q000139:chemically induced / Q000503:physiopathology*; D003214:Conditioning, Classical / Q000187:drug effects / Q000502:physiology*; D018691:Excitatory Amino Acid Antagonists / Q000008:administration & dosage / Q000633:toxicity; D005239:Fear / Q000187:drug effects / Q000502:physiology*; D006624:Hippocampus / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D008568:Memory / Q000187:drug effects / Q000502:physiology; D008845:Microinjections; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology*; D013216:Reflex, Startle / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D015763:2-Amino-5-phosphonovalerate