Strain differences in fear between spontaneously hypertensive and normotensive rats

Joseph Ledoux, A. Sakaguchi, D. J. Reis

Research output: Contribution to journalArticle

Abstract

The purpose of this study was to determine whether the reduced conditioned fear response in spontaneously hypertensive rats (SHRs) relative to Wistar-Kyoto controls (WKYs): (a) reflects a decrease in fear in SHRs or an increase in fear in WKYs, relative to other strains; (b) is secondary to strain differences in cardiovascular regulation; (c) represents a weaker conditioned response or a weaker memory trace; and (d) generalizes beyond tests of conditioned fear. SHRs, WKYs and Sprague-Dawley (SD) rats were subjected to classical fear conditioning (30 trials) involving the pairing of a tone conditioned emotional stimulus (CES: 800 Hz, 82 dB, 10 s) with an electric footshock unconditioned stimulus (US: 1.5 mA, 0.5 s). Cardiovascular responses elicited by the CES (without the US) were assessed through computer assisted techniques in chronically instrumented animals. Conditioned fear behavior was assessed as the proportion of time accounted for by crouching or freezing during a 300s presentation of the CES without the US. Unconditioned fear reactivity was examined using the open field test. Conditioned fear reactivity (% freezing during 300 s CES) was reduced (P < 0.01) in SHRs relative to both WKYs and SDs, which did not differ (SHR: 57% ± 5; WKY 85% ± 3; SD: 93% ± 4). Young (7 week) and mature (14 week) animals within each strain differed in resting mean arterial pressure (MAP, in mm Hg) (WKY: young, 102 ± 1; mature, 133 ± 2; P < 0.01; SHR: young, 124 ± 3 mature, 153 ± 5; P < 0.01) but did not differ in conditioned fear reactivity (WKY: young, 91% ± 3; mature, 93% ± 3; SHR: young, 47% ± 3; mature, 62% ± 8). The conditioned pressor response (peak value in mm Hg) was greater (P < 0.05) in mature (25 ±2) than in young (16 ± 2) SHRs, although conditioned freezing did not differ (see above). In mature SHRs, conditioned freezing did not differ 15 min (49% ± 6) and 24 h (55% ± 6) after conditioning. In the open field, SHRs spent less time (in s) in the center square initially (WKY 18 ± 4; SHR: 3 ± 2, P < 0.01), crossed more squares in 3 min (WKY: 12 ± 3; SHR: 37 ± 4, P < 0.01) and defecated less (WKY 2 ± 1; SHR 0; P < 0.05) than WKYs. These findings demonstrate that the strain difference in conditioned fear represents a reduction in fear reactivity in SHRs relative to normotensive rats, is independent of strain differences in cardiovascular regulation, involves the establishment of a weaker conditioned response rather than a memory deficit, and generalizes beyond tests of conditioned fear.

Original languageEnglish (US)
Pages (from-to)137-143
Number of pages7
JournalBrain Research
Volume277
Issue number1
DOIs
StatePublished - Oct 24 1983

Fingerprint

Inbred SHR Rats
Fear
Freezing
Classical Conditioning
Memory Disorders
Sprague Dawley Rats
Arterial Pressure

Keywords

  • classical conditioning
  • emotion
  • fear
  • spontaneously hypertensive rats
  • strain differences

ASJC Scopus subject areas

  • Developmental Biology
  • Molecular Biology
  • Clinical Neurology
  • Neuroscience(all)

Cite this

Strain differences in fear between spontaneously hypertensive and normotensive rats. / Ledoux, Joseph; Sakaguchi, A.; Reis, D. J.

In: Brain Research, Vol. 277, No. 1, 24.10.1983, p. 137-143.

Research output: Contribution to journalArticle

Ledoux, Joseph ; Sakaguchi, A. ; Reis, D. J. / Strain differences in fear between spontaneously hypertensive and normotensive rats. In: Brain Research. 1983 ; Vol. 277, No. 1. pp. 137-143.
@article{e7bae4300f2f488aa79f21ebd0856f4a,
title = "Strain differences in fear between spontaneously hypertensive and normotensive rats",
abstract = "The purpose of this study was to determine whether the reduced conditioned fear response in spontaneously hypertensive rats (SHRs) relative to Wistar-Kyoto controls (WKYs): (a) reflects a decrease in fear in SHRs or an increase in fear in WKYs, relative to other strains; (b) is secondary to strain differences in cardiovascular regulation; (c) represents a weaker conditioned response or a weaker memory trace; and (d) generalizes beyond tests of conditioned fear. SHRs, WKYs and Sprague-Dawley (SD) rats were subjected to classical fear conditioning (30 trials) involving the pairing of a tone conditioned emotional stimulus (CES: 800 Hz, 82 dB, 10 s) with an electric footshock unconditioned stimulus (US: 1.5 mA, 0.5 s). Cardiovascular responses elicited by the CES (without the US) were assessed through computer assisted techniques in chronically instrumented animals. Conditioned fear behavior was assessed as the proportion of time accounted for by crouching or freezing during a 300s presentation of the CES without the US. Unconditioned fear reactivity was examined using the open field test. Conditioned fear reactivity ({\%} freezing during 300 s CES) was reduced (P < 0.01) in SHRs relative to both WKYs and SDs, which did not differ (SHR: 57{\%} ± 5; WKY 85{\%} ± 3; SD: 93{\%} ± 4). Young (7 week) and mature (14 week) animals within each strain differed in resting mean arterial pressure (MAP, in mm Hg) (WKY: young, 102 ± 1; mature, 133 ± 2; P < 0.01; SHR: young, 124 ± 3 mature, 153 ± 5; P < 0.01) but did not differ in conditioned fear reactivity (WKY: young, 91{\%} ± 3; mature, 93{\%} ± 3; SHR: young, 47{\%} ± 3; mature, 62{\%} ± 8). The conditioned pressor response (peak value in mm Hg) was greater (P < 0.05) in mature (25 ±2) than in young (16 ± 2) SHRs, although conditioned freezing did not differ (see above). In mature SHRs, conditioned freezing did not differ 15 min (49{\%} ± 6) and 24 h (55{\%} ± 6) after conditioning. In the open field, SHRs spent less time (in s) in the center square initially (WKY 18 ± 4; SHR: 3 ± 2, P < 0.01), crossed more squares in 3 min (WKY: 12 ± 3; SHR: 37 ± 4, P < 0.01) and defecated less (WKY 2 ± 1; SHR 0; P < 0.05) than WKYs. These findings demonstrate that the strain difference in conditioned fear represents a reduction in fear reactivity in SHRs relative to normotensive rats, is independent of strain differences in cardiovascular regulation, involves the establishment of a weaker conditioned response rather than a memory deficit, and generalizes beyond tests of conditioned fear.",
keywords = "classical conditioning, emotion, fear, spontaneously hypertensive rats, strain differences",
author = "Joseph Ledoux and A. Sakaguchi and Reis, {D. J.}",
year = "1983",
month = "10",
day = "24",
doi = "10.1016/0006-8993(83)90915-0",
language = "English (US)",
volume = "277",
pages = "137--143",
journal = "Brain Research",
issn = "0006-8993",
publisher = "Elsevier",
number = "1",

}

TY - JOUR

T1 - Strain differences in fear between spontaneously hypertensive and normotensive rats

AU - Ledoux, Joseph

AU - Sakaguchi, A.

AU - Reis, D. J.

PY - 1983/10/24

Y1 - 1983/10/24

N2 - The purpose of this study was to determine whether the reduced conditioned fear response in spontaneously hypertensive rats (SHRs) relative to Wistar-Kyoto controls (WKYs): (a) reflects a decrease in fear in SHRs or an increase in fear in WKYs, relative to other strains; (b) is secondary to strain differences in cardiovascular regulation; (c) represents a weaker conditioned response or a weaker memory trace; and (d) generalizes beyond tests of conditioned fear. SHRs, WKYs and Sprague-Dawley (SD) rats were subjected to classical fear conditioning (30 trials) involving the pairing of a tone conditioned emotional stimulus (CES: 800 Hz, 82 dB, 10 s) with an electric footshock unconditioned stimulus (US: 1.5 mA, 0.5 s). Cardiovascular responses elicited by the CES (without the US) were assessed through computer assisted techniques in chronically instrumented animals. Conditioned fear behavior was assessed as the proportion of time accounted for by crouching or freezing during a 300s presentation of the CES without the US. Unconditioned fear reactivity was examined using the open field test. Conditioned fear reactivity (% freezing during 300 s CES) was reduced (P < 0.01) in SHRs relative to both WKYs and SDs, which did not differ (SHR: 57% ± 5; WKY 85% ± 3; SD: 93% ± 4). Young (7 week) and mature (14 week) animals within each strain differed in resting mean arterial pressure (MAP, in mm Hg) (WKY: young, 102 ± 1; mature, 133 ± 2; P < 0.01; SHR: young, 124 ± 3 mature, 153 ± 5; P < 0.01) but did not differ in conditioned fear reactivity (WKY: young, 91% ± 3; mature, 93% ± 3; SHR: young, 47% ± 3; mature, 62% ± 8). The conditioned pressor response (peak value in mm Hg) was greater (P < 0.05) in mature (25 ±2) than in young (16 ± 2) SHRs, although conditioned freezing did not differ (see above). In mature SHRs, conditioned freezing did not differ 15 min (49% ± 6) and 24 h (55% ± 6) after conditioning. In the open field, SHRs spent less time (in s) in the center square initially (WKY 18 ± 4; SHR: 3 ± 2, P < 0.01), crossed more squares in 3 min (WKY: 12 ± 3; SHR: 37 ± 4, P < 0.01) and defecated less (WKY 2 ± 1; SHR 0; P < 0.05) than WKYs. These findings demonstrate that the strain difference in conditioned fear represents a reduction in fear reactivity in SHRs relative to normotensive rats, is independent of strain differences in cardiovascular regulation, involves the establishment of a weaker conditioned response rather than a memory deficit, and generalizes beyond tests of conditioned fear.

AB - The purpose of this study was to determine whether the reduced conditioned fear response in spontaneously hypertensive rats (SHRs) relative to Wistar-Kyoto controls (WKYs): (a) reflects a decrease in fear in SHRs or an increase in fear in WKYs, relative to other strains; (b) is secondary to strain differences in cardiovascular regulation; (c) represents a weaker conditioned response or a weaker memory trace; and (d) generalizes beyond tests of conditioned fear. SHRs, WKYs and Sprague-Dawley (SD) rats were subjected to classical fear conditioning (30 trials) involving the pairing of a tone conditioned emotional stimulus (CES: 800 Hz, 82 dB, 10 s) with an electric footshock unconditioned stimulus (US: 1.5 mA, 0.5 s). Cardiovascular responses elicited by the CES (without the US) were assessed through computer assisted techniques in chronically instrumented animals. Conditioned fear behavior was assessed as the proportion of time accounted for by crouching or freezing during a 300s presentation of the CES without the US. Unconditioned fear reactivity was examined using the open field test. Conditioned fear reactivity (% freezing during 300 s CES) was reduced (P < 0.01) in SHRs relative to both WKYs and SDs, which did not differ (SHR: 57% ± 5; WKY 85% ± 3; SD: 93% ± 4). Young (7 week) and mature (14 week) animals within each strain differed in resting mean arterial pressure (MAP, in mm Hg) (WKY: young, 102 ± 1; mature, 133 ± 2; P < 0.01; SHR: young, 124 ± 3 mature, 153 ± 5; P < 0.01) but did not differ in conditioned fear reactivity (WKY: young, 91% ± 3; mature, 93% ± 3; SHR: young, 47% ± 3; mature, 62% ± 8). The conditioned pressor response (peak value in mm Hg) was greater (P < 0.05) in mature (25 ±2) than in young (16 ± 2) SHRs, although conditioned freezing did not differ (see above). In mature SHRs, conditioned freezing did not differ 15 min (49% ± 6) and 24 h (55% ± 6) after conditioning. In the open field, SHRs spent less time (in s) in the center square initially (WKY 18 ± 4; SHR: 3 ± 2, P < 0.01), crossed more squares in 3 min (WKY: 12 ± 3; SHR: 37 ± 4, P < 0.01) and defecated less (WKY 2 ± 1; SHR 0; P < 0.05) than WKYs. These findings demonstrate that the strain difference in conditioned fear represents a reduction in fear reactivity in SHRs relative to normotensive rats, is independent of strain differences in cardiovascular regulation, involves the establishment of a weaker conditioned response rather than a memory deficit, and generalizes beyond tests of conditioned fear.

KW - classical conditioning

KW - emotion

KW - fear

KW - spontaneously hypertensive rats

KW - strain differences

UR - http://www.scopus.com/inward/record.url?scp=0020637597&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0020637597&partnerID=8YFLogxK

U2 - 10.1016/0006-8993(83)90915-0

DO - 10.1016/0006-8993(83)90915-0

M3 - Article

VL - 277

SP - 137

EP - 143

JO - Brain Research

JF - Brain Research

SN - 0006-8993

IS - 1

ER -