TY - JOUR
T1 - Facilitation of cardiac vagal activity by CRF-R1 antagonists during swim stress in rats
AU - Wood, Susan K.
AU - Verhoeven, Robert E.
AU - Savit, Aaron Z.
AU - Rice, Kenner C.
AU - Fischbach, Peter S.
AU - Woods, James H.
N1 - Funding Information:
We would like to thank Dr Jean Rivier and his laboratory (Salk Institute; La Jolla, CA) for the generous donation of astressin B used in these studies. This research was supported by USPHS Grants DA14349 and GM07767.
PY - 2006/12/4
Y1 - 2006/12/4
N2 - Exposure to stressors that elicit fear and feelings of hopelessness can cause severe vagal activation leading to bradycardia, syncope, and sudden death. These phenomena though documented, are difficult to diagnose, treat clinically, and prevent. Therefore, an animal model incorporating these cardiovascular conditions could be useful. The present study examined 'sinking' during a 2-h swim stress, a phenomenon that occurs in 50% of rats during 25°C water exposure. Concurrent measurements of body temperature, immobility, heart rate (HR), and PR interval (a measure of vagal activity) were made. Neither decreases in immobility nor variations in hypothermia during swim were correlated with sinking. Bradycardia was more severe in sinking rats (average minimum HR±SEM; 143±13 vs 247±14; p<0.01), and PR interval was elevated (p<0.0001). To examine potential modulation of vagal activity during stress, corticotropin-relasing factor (CRF) receptor antagonists (antalarmin, R121919 and astressin B), a glucocorticoid receptor antagonist (RU486), and a peripherally acting cholinergic antagonist (methylatropine nitrate) were administered. The centrally acting CRF antagonist, antalarmin (32 mg/kg), produced elongation of the PR interval (p<0.0001), robust bradycardia (135±18; p<0.001), and increased sinking (92%; p<0.05), and methylatropine nitrate (3.2 mg/kg) blocked these effects. Corroborating these data, two different CRF antagonists, R121919 (30 mg/kg) and astressin B (intracerebroventricular (i.c.v.), 0.03 μg/rat) increased sinking to 100%. RU486 (20 mg/kg) blocked HPA axis negative feedback and decreased percent sinking to 25%. From these studies, we concluded that sinking during a 2-h water exposure was a result of extreme vagal hyperactivity. Furthermore, stress-induced CRF release may serve to protect against elevated cardiac vagal activity.
AB - Exposure to stressors that elicit fear and feelings of hopelessness can cause severe vagal activation leading to bradycardia, syncope, and sudden death. These phenomena though documented, are difficult to diagnose, treat clinically, and prevent. Therefore, an animal model incorporating these cardiovascular conditions could be useful. The present study examined 'sinking' during a 2-h swim stress, a phenomenon that occurs in 50% of rats during 25°C water exposure. Concurrent measurements of body temperature, immobility, heart rate (HR), and PR interval (a measure of vagal activity) were made. Neither decreases in immobility nor variations in hypothermia during swim were correlated with sinking. Bradycardia was more severe in sinking rats (average minimum HR±SEM; 143±13 vs 247±14; p<0.01), and PR interval was elevated (p<0.0001). To examine potential modulation of vagal activity during stress, corticotropin-relasing factor (CRF) receptor antagonists (antalarmin, R121919 and astressin B), a glucocorticoid receptor antagonist (RU486), and a peripherally acting cholinergic antagonist (methylatropine nitrate) were administered. The centrally acting CRF antagonist, antalarmin (32 mg/kg), produced elongation of the PR interval (p<0.0001), robust bradycardia (135±18; p<0.001), and increased sinking (92%; p<0.05), and methylatropine nitrate (3.2 mg/kg) blocked these effects. Corroborating these data, two different CRF antagonists, R121919 (30 mg/kg) and astressin B (intracerebroventricular (i.c.v.), 0.03 μg/rat) increased sinking to 100%. RU486 (20 mg/kg) blocked HPA axis negative feedback and decreased percent sinking to 25%. From these studies, we concluded that sinking during a 2-h water exposure was a result of extreme vagal hyperactivity. Furthermore, stress-induced CRF release may serve to protect against elevated cardiac vagal activity.
KW - Antalarmin
KW - Astressin B
KW - CRF antagonists
KW - Cardiac vagal activity
KW - R121919
KW - Swim stress
UR - http://www.scopus.com/inward/record.url?scp=33751080599&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33751080599&partnerID=8YFLogxK
U2 - 10.1038/sj.npp.1301085
DO - 10.1038/sj.npp.1301085
M3 - Article
C2 - 16710322
AN - SCOPUS:33751080599
VL - 31
SP - 2580
EP - 2590
JO - Neuropsychopharmacology
JF - Neuropsychopharmacology
SN - 0893-133X
IS - 12
ER -