Effects of ascorbic acid on lead induced alterations of synaptic transmission and contractile features in murine dorsiflexor muscle.
Lead is a common environmental toxin that affects neuromuscular junction and potentially might cause muscle weakness. Antioxidants like ascorbic acid may protect against lead induced myopathy. The present study measured isometric twitch tensions (evoked either directly by muscle stimulation or indirectly by nerve stimulation) to study effects of ascorbic acid on lead induced alterations at murine dorsiflexor skeletal muscle. Resting membrane potentials (RMPs), endplate potentials (EPPs) and miniature endplate potentials (MEPPs) were also recorded. Forty animals were divided into four groups of n = 10 each. (10 control, 10 lead alone, 10 ascorbic acid alone, 10 lead treated plus ascorbic acid). Lead (1 mg/kg) i.p, was administered daily for 2 weeks before the recording day and ascorbic acid (200 mg/kg, i.p) was given daily for 3 weeks prior to the experiment day. Lead treatment reduced twitch tension significantly (from 4.3 +/- 0.5 g to 2.7 +/- 0.2 g) and delayed half time of decay compared to the control. Similarly MEPPs frequencies were reduced following lead treatment. Application of ascorbic acid prevented twitch tension reduction in lead treated mice (3.3 +/- 0.3 g) and reversed lead induced delay in half time of decay. The negative actions of lead treatment on MEPPs frequencies were also modified with ascorbic acid. It appears that ascorbic acid exerts a protective role against lead induced peripheral nerve and muscle dysfunction. This effect of ascorbic acid on lead induced neuromyopathy is probably mediated via a free radical scavenging mechanism or modification of Ca(2+) homeostasis.
Hasan
M Y
MY
Department of Pharmacology, Faculty of Medicine, UAE University, PO Box 17666, Al Ain, United Arab Emirates. my.hasan@uaeu.ac.ae
Alshuaib
W B
WB
Singh
S
S
Fahim
M A
MA
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000494:pharmacology*; D001835:Body Weight / Q000187:drug effects; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D007854:Lead / Q000037:antagonists & inhibitors* / Q000097:blood / Q000633:toxicity*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D009045:Motor Endplate / Q000187:drug effects / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000294:innervation / Q000378:metabolism; D018377:Neurotransmitter Agents / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects*
D000975:Antioxidants; D018377:Neurotransmitter Agents; D007854:Lead; D001205:Ascorbic Acid