Contextual fear conditioning is associated with an increase of acetylcholine release in the hippocampus of rat

• Published in: Brain research. Cognitive brain research Vol. 9; no. 2; pp. 193 - 197
• Main Authors: Nail-Boucherie, K, Dourmap, N, Jaffard, R, Costentin, J
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.03.2000; Elsevier Science
• Subjects: Acetylcholine - metabolism; Acetylcholine release; Animal; Animals; Behavior, Animal - physiology; Biological and medical sciences; Conditioning (Psychology) - physiology; Contextual fear conditioning; Electroshock; Extracellular Space - metabolism; Fear - physiology; Foot-shock; Fundamental and applied biological sciences. Psychology; Hippocampus; Hippocampus - metabolism; Learning; Learning. Memory; Male; Microdialysis; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Rat; Rats; Rats, Sprague-Dawley; Retention (Psychology) - physiology; Rat; Foot-shock; LS=lateral septum; MS/VDB=medial septum/vertical limb nucleus of the diagonal band of Broca; Contextual fear conditioning; Acetylcholine release; Hippocampus; ACh=acetylcholine; Noxious stimulus; Rodentia; Experimental study; Retention; Classical conditioning; Learning; Vertebrata; Mammalia; Acquisition process; Microdialysis; Investigation method; Animal; Neurotransmitter; Acetylcholine; Tonic immobility; Brain (vertebrata)
• ISSN: 0926-6410
• DOI: 10.1016/S0926-6410(99)00058-0

The effects of contextual fear conditioning on the release of acetylcholine (ACh) in the hippocampus of freely moving rats was assessed using microdialysis. Measures were carried out during both acquisition and retention testing (re-exposure to the conditioning chamber) and compared between animals that either received foot-shocks as unconditioned stimulus (conditioned group) or no foot-shocks (control group) during acquisition. Results showed that during acquisition, hippocampal ACh extracellular level was increased with respect to baseline but that this increase was of similar magnitude in both groups. By contrast, re-exposure to the conditioning chamber the day after (retention testing) produced a significantly greater increase in ACh extracellular level in the conditioned (that, otherwise, displayed conditioned freezing behavior to contextual cues), than in the control group (which displayed virtually no freezing). This enhanced hippocampal ACh release seems to result from the greater hippocampal processing of contextual stimuli in conditioned animals with respect to controls.