Cholinergic transmission in the dorsal hippocampus modulates trace but not delay fear conditioning.
Although cholinergic mechanisms have been widely implicated in learning and memory processes, few studies have investigated the specific contribution of hippocampal cholinergic transmission during trace fear conditioning, a form of associative learning involving a temporal gap between two stimuli. Microinfusions of scopolamine, a muscarinic receptor antagonist, into the dorsal hippocampus (DH) produced dose-dependent impairment in the acquisition and expression of a conditioned response (CR) following trace fear conditioning with a tone conditioned stimulus (CS) and a footshock unconditioned stimulus (US) in rats. The same infusions, however, had no effect on delay conditioning, general activity, pain sensitivity or attentional modulation. Moreover, scopolamine infusions attenuated phosphorylation of extracellular signal-regulated kinase (ERK) in the amygdala, indicating that cholinergic signals in the DH are important for trace fear conditioning. Taken together, the current study provides evidence that cholinergic neurotransmission in the DH is essential for the cellular processing of CS-US association in the amygdala when the two stimuli are temporally disconnected.
Pang
Min-Hee
MH
Department of Psychology, Korea University, Seoul, Republic of Korea.
Kim
Nam-Soo
NS
Kim
Il-Hwan
IH
Kim
Hyun
H
Kim
Hyun-Taek
HT
Choi
June-Seek
JS
D000679:Amygdala / Q000201:enzymology; D000704:Analysis of Variance; D000818:Animals; D001245:Association Learning / Q000187:drug effects / Q000502:physiology*; D018680:Cholinergic Antagonists / Q000008:administration & dosage; D002799:Cholinergic Fibers / Q000187:drug effects / Q000502:physiology*; D003214:Conditioning, Classical / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D048049:Extracellular Signal-Regulated MAP Kinases / Q000187:drug effects / Q000378:metabolism; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008845:Microinjections; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012153:Retention, Psychology / Q000187:drug effects / Q000502:physiology*; D012601:Scopolamine / Q000008:administration & dosage; D018709:Statistics, Nonparametric; D013997:Time Factors
D018680:Cholinergic Antagonists; D012601:Scopolamine; D048049:Extracellular Signal-Regulated MAP Kinases