Effects of acrylamide and some other sulfhydryl reagents on spontaneous and pathologically induced terminal sprouting from motor end-plates.

Abstract

The innervation of the normal rat sternocostalis muscle exhibits a constant low level of short spontaneous terminal sprouts visible in zinc iodide-osmium (ZIO) and in methylene blue-stained preparations. Acrylamide inhibits these spontaneous sprouts in a dose-dependent manner. This inhibition is mimicked by N-ethylmaleimide (a sulfhydryl group blocking agent) and can be nullified when acrylamide is given after the sulfhydryl group protecting agent, dithiothreitol (DTT). This could not be reversed by giving DTT 3 hours after acrylamide. Furthermore, when given alone DTT increases the level of spontaneous terminal sprouting seen in ZIO and in methylene blue-stained preparations. These findings suggest that the binding of acrylamide to sulfhydryl groups is involved in the inhibitory process. Acrylamide also reduces the number and length of the reactionary terminal sprouts, seen in ZIO and in methylene blue-stained preparations, that follow partial denervation or local injection of botulinum toxin. These inhibitory effects are long-lasting; recovery still has not fully occurred 4 weeks after a single dose of acrylamide (50 mg/kg). The roles of glutathione and other sulfhydryl components of axons are discussed in relation to the mechanism of acrylamide neurotoxicity.