The Maudsley Reactive and Nonreactive strains: a new perspective

Area of Science:

• Neuroscience
• Behavioral Genetics
• Animal Models

Background:

• The Maudsley Reactive (MR/Har) and Maudsley Nonreactive (MNRA/Har) rat strains were selectively bred for emotionality differences.
• Decades of research have explored their behavioral and physiological distinctions.

Purpose of the Study:

• To review and synthesize research on the Maudsley Reactive and Maudsley Nonreactive rat strains.
• To examine phenotypic differences beyond the original selection criteria for emotionality.

Main Methods:

• Review of studies conducted between 1980 and 2001 on MR/Har and MNRA/Har rat strains.
• Analysis of behavioral data from conflict situations, fear conditioning, elevated plus maze, ethanol preference tests, and novelty exploration.
• Examination of peripheral sympathetic nervous system (PSNS) activity and central noradrenergic system responses.

Main Results:

• Consistent strain differences in conflict behavior support emotionality distinctions.
• Inconsistent or absent differences in fear-related tasks (escape-avoidance, elevated plus maze).
• MR/Har rats show greater ethanol preference and novelty exploration; PSNS alterations correlate with open-field defecation (OFD).

Conclusions:

• Phenotypic differences in Maudsley strains often extend beyond original selection criteria.
• Ethanol preference and novelty response in MR/Har rats may offer insights into alcoholism and anxiety research.
• PSNS and central noradrenergic system differences suggest genetic influences on stress response and emotionality, potentially requiring re-evaluation of OFD as a sole emotionality index.