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DUAL ACTIVATION OF CARDIAC SYMPATHETIC AND PARASYMPATHETIC COMPONENTS DURING CONDITIONED FEAR TO CONTEXT IN THE RAT
Author(s) -
Carrive Pascal
Publication year - 2006
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.2006.04519.x
Subject(s) - atropine , propranolol , muscarinic acetylcholine receptor , parasympathetic nervous system , antagonist , medicine , heart rate , endocrinology , context (archaeology) , anesthesia , muscarinic antagonist , psychology , autonomic nervous system , blood pressure , receptor , biology , paleontology
SUMMARY1 The present study investigates the contribution of the sympathetic and vagal parasympathetic systems to the tachycardic response of long‐lasting (40 min) conditioned fear responses to context. 2 The conditioned fear response evoked by re‐exposure to a footshock chamber was tested 10 min after intravenous injection of the β‐adrenoceptor antagonist propranolol (2 mg/kg) or the muscarinic antagonist atropine methyl nitrate (2 mg/kg) in rats implanted with radiotelemetric probes. 3 Compared with saline controls, the drugs did not change the behavioural component of the response (freezing, 22 kHz ultrasonic vocalizations) or its pressor component (+28 mmHg). 4 Propranolol abolished the tachycardic response of fear, whereas atropine more than doubled it (from +75 to +175 b.p.m. above resting baseline). 5 The results demonstrate that both sympathetic and vagal parasympathetic outflows to the heart are strongly activated during conditioned fear. The vagal activation may act to hold back cardiac acceleration while the animal waits for the aversive stimulus to come.