Constancy of masseter muscle structure and function with age in F344 rats

Area of Science:

• Gerontology
• Muscle Physiology
• Biomechanical Engineering

Background:

• Senile muscle atrophy is common with aging, but masticatory muscles are understudied.
• Understanding age-related changes in jaw muscles is crucial for maintaining oral function.

Purpose of the Study:

• To establish a rat masseter muscle preparation for in vitro contractile studies.
• To investigate age-related changes in masseter muscle composition and function.

Main Methods:

• Developed an in vitro masseter muscle preparation from male Fischer 344 rats (4-24 months old).
• Utilized histochemical analysis (myosin ATPase, NADH-TR, toluidine blue) for fibre typing and sizing.
• Assessed isometric contractile properties and tissue composition (dry:wet weight ratio).

Main Results:

• The anterior deep masseter is suitable for in vitro studies due to its thinness.
• No significant differences in muscle fibre type, size, or contractile properties were observed between young and old rats.
• Masticatory muscle composition and function remained largely unchanged with age in this model.

Conclusions:

• The anterior deep masseter preparation is viable for studying masseter muscle function in vitro.
• Age-related decline in masticatory muscle performance may not occur in rats.
• Findings contrast with some studies on aging rodent limb muscles, highlighting preserved jaw muscle function.