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Methylmercury induced neuromuscular dysfunction in the rat.
1Department of Pharmacology and Toxicology, University of Rochester, School of Medicine and Dentistry, Rochester, N.Y. U.S.A.
Neuroscience Letters
|July 17, 2009
Summary
Methylmercury exposure in rats impairs phrenic nerve-hemidiaphragm function, reducing muscle contraction strength. This neurotoxicity may explain the observed muscular weakness in methylmercury intoxication.
Area of Science:
- Neuroscience
- Toxicology
- Physiology
Background:
- Methylmercury is a potent neurotoxin.
- Muscular weakness is a symptom of methylmercury intoxication.
Purpose of the Study:
- To investigate the effects of methylmercury on neuromuscular function.
- To elucidate the mechanisms underlying methylmercury-induced muscle weakness.
Main Methods:
- Rats were exposed to methylmercury (20 mg/kg) for 10-18 days.
- Isolated phrenic nerve-hemidiaphragm preparations were used to assess muscle function.
- Muscle contraction amplitude and response to neostigmine were measured.
- Effects of methylmercury on nerve action potentials were evaluated.
Main Results:
- Methylmercury exposure reduced the ability of phrenic nerve-hemidiaphragms to maintain contraction amplitude.
- Neostigmine showed a significantly lower contraction enhancement in exposed animals.
- In vitro, methylmercury (2 x 10(-5) M) inhibited contractions with minimal recovery.
- Muscle response to direct stimulation and nerve action potentials remained largely unaffected.
Conclusions:
- Methylmercury directly impairs neuromuscular transmission, leading to reduced muscle contractility.
- The observed neuromuscular dysfunction likely contributes to the muscular weakness seen in methylmercury intoxication.
- The phrenic nerve-hemidiaphragm is a sensitive model for studying methylmercury's neurotoxic effects.
