Strain differences in fear between spontaneously hypertensive and normotensive rats

Area of Science:

• Neuroscience
• Behavioral Science
• Cardiovascular Science

Background:

• Spontaneously hypertensive rats (SHRs) show reduced conditioned fear responses compared to control strains.
• Investigating the underlying mechanisms of this reduced fear response is crucial for understanding fear processing and its relation to hypertension.

Purpose of the Study:

• To determine if reduced fear in SHRs is due to decreased fear, increased fear in controls, cardiovascular regulation differences, or weaker memory traces.
• To assess if the reduced fear response in SHRs generalizes beyond classical fear conditioning tests.

Main Methods:

• Classical fear conditioning was performed on SHRs, Wistar-Kyoto controls (WKYs), and Sprague-Dawley (SD) rats using auditory conditioned stimulus (CS) and footshock unconditioned stimulus (US).
• Cardiovascular responses to the CS were measured in instrumented animals.
• Conditioned fear behavior (freezing) and unconditioned fear reactivity (open field test) were assessed.

Main Results:

• SHRs displayed significantly reduced conditioned fear reactivity (% freezing) compared to both WKYs and SD rats.
• No significant differences in conditioned fear reactivity were observed between young and mature animals within each strain, despite age-related differences in mean arterial pressure.
• Cardiovascular responses to the conditioned stimulus were not detailed in the provided abstract excerpt.

Conclusions:

• The reduced conditioned fear response in SHRs is a genuine strain-specific difference, not attributable to increased fear in controls or age-related cardiovascular changes.
• The findings suggest a specific deficit in fear conditioning or memory consolidation in SHRs, independent of their hypertensive state.
• Further research is needed to explore the generalization of this reduced fear response and its neurobiological underpinnings.