title: Nucleus accumbens carbachol disrupts olfactory and contextual fear-potentiated startle and attenuates baseline startle reactivity.
abstract: Although the nucleus accumbens (NAc) typically is not considered a primary component of the circuitry underlying either the acquisition or retrieval of conditioned fear, evidence suggests that this region may play some role in modulating fear-related behaviors. The goal of the present study was to explore a potential role for NAc cholinergic receptors in the expression of fear-potentiated startle (FPS) and baseline startle reactivity. Intra-NAc infusion of the broad-acting cholinergic receptor agonist, carbachol, suppressed FPS elicited by re-exposure to both a discrete odor previously paired with footshock and the conditioning context. Although carbachol elevated spontaneous motor activity, activity bouts did not account for startle suppression in carbachol-treated Ss. In addition, intra-NAc carbachol suppressed baseline startle over a range of acoustic pulse intensities in the absence of explicit fear conditioning. Collectively, these findings suggest that NAc cholinergic receptors play a role in the modulation of baseline startle reactivity, rather than in the retrieval of learned fear, and that this role is independent of overt motor activity.
authors.affiliation: Department of Psychology, Drew University, 36 Madison Avenue, Madison, NJ 07940, United States. gcousens@drew.edu
authors.forename: Graham A
authors.initials: GA
authors.lastname: Cousens
authors.forename: Cheryl G
authors.initials: CG
authors.lastname: Skrobacz
authors.forename: Anna
authors.initials: A
authors.lastname: Blumenthal
mesh_terms: D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects / Q000502:physiology; D002217:Carbachol / Q000494:pharmacology*; D018679:Cholinergic Agonists / Q000494:pharmacology*; D002799:Cholinergic Fibers / Q000187:drug effects / Q000502:physiology; D003214:Conditioning, Classical / Q000187:drug effects / Q000502:physiology; D005239:Fear / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008845:Microinjections; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology; D009714:Nucleus Accumbens / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013216:Reflex, Startle / Q000187:drug effects / Q000502:physiology*; D012153:Retention, Psychology / Q000187:drug effects / Q000502:physiology; D012903:Smell
chemical_list: D018679:Cholinergic Agonists; D002217:Carbachol