Fear potentiation of acoustic startle stimulus-evoked heart rate changes in rats.
The present study examined the extent to which heart rate changes evoked by acoustic startle stimuli are affected by the development of fear during startle testing. The phasic heart rate responses of rats elicited by a 120-dB startle stimulus were characterized by decelerations that habituated across trials and accelerations that developed across trials in a manner that paralleled the development of freezing behavior. A 92-dB stimulus evoked little freezing or tachycardia, yet evoked decelerations of similar magnitude to the 120-dB stimulus. Pharmacological blockade of autonomic activity was used to uncouple freezing from the heart rate accelerations and to show that the accelerations were not an artifact of the habituating decelerations. These results indicate that heart rate responses to nonsignal stimuli depend critically on a rat's previous experience with those stimuli.
Young
B J
BJ
Center for Behavioral Neuroscience, State University of New York, Stony Brook 11794-2575.
Leaton
R N
RN
D000161:Acoustic Stimulation; D000818:Animals; D001143:Arousal / Q000187:drug effects / Q000502:physiology; D001262:Atenolol / Q000494:pharmacology; D001286:Atropine Derivatives / Q000494:pharmacology; D001341:Autonomic Nervous System / Q000187:drug effects / Q000502:physiology; D003214:Conditioning, Classical / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D005239:Fear / Q000187:drug effects / Q000502:physiology; D006185:Habituation, Psychophysiologic / Q000187:drug effects / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D008144:Loudness Perception / Q000187:drug effects / Q000502:physiology; D008297:Male; D011939:Mental Recall / Q000187:drug effects / Q000502:physiology; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D010276:Parasympatholytics / Q000494:pharmacology; D051381:Rats; D013216:Reflex, Startle / Q000187:drug effects / Q000502:physiology
D001286:Atropine Derivatives; D010276:Parasympatholytics; D001262:Atenolol; C006649:methylatropine