Cholinesterase activity of nodal and internodal regions of myelinated nerve fibers of frog.
The distribution of cholinesterase (Ch-esterase) in isolated myelinated fibers of the frog has been investigated. Quantitative microgasometric measurements have confirmed the previous histochemical observations. Both approaches indicate that in frog nerve fibers acetylcholinesterase (ACh-esterase) is the only or the predominant enzyme when selective inhibitors and different substrates are used: acetylcholine (ACh), butyrylcholine, and acetyl-B-methylcholine (Mecholyl). By means of the microgasometric technique, a significant difference in ACh-esterase activity between axons isolated from ventral (37.2 +/- 1.7 micromole x 10(-5) ACh/mm(2)/hr) and dorsal roots (2.0 +/- 0.9 micromole x 10(-5) ACh/mm(2)/hr) was found. In the region of the node of Ranvier the enzyme activity (50.4 +/- 4.4 micromole x 10(-5) ACh/mm(2)/hr) appears to be considerably higher than in the internodal area (36.6 +/- 2.1 micromole x 10(-5) ACh/mm(2)/hr). The findings are discussed in relation to the theory of saltatory conduction and the ACh system.
D000109:Acetylcholine / Q000494:pharmacology; D000110:Acetylcholinesterase / Q000378:metabolism; D000818:Animals; D001001:Anura; D001369:Axons / Q000201:enzymology; D002802:Cholinesterases / Q000378:metabolism*; D005727:Ganglia, Spinal / Q000201:enzymology; D006651:Histocytochemistry; D008688:Methacholine Compounds / Q000494:pharmacology; D009186:Myelin Sheath / Q000201:enzymology*; D009474:Neurons / Q000032:analysis; D011901:Ranvier's Nodes / Q000201:enzymology; D012584:Sciatic Nerve / Q000201:enzymology
D008688:Methacholine Compounds; D000110:Acetylcholinesterase; D002802:Cholinesterases; D000109:Acetylcholine