title: The effects of acute and chronic botulinum toxin treatment on receptor number, receptor distribution and tissue sensitivity in rat diaphragm.
abstract: Tritiated alpha-bungarotoxin was used to determine the number and distribution of acetylcholine receptors in innervated, denervated and botulinum toxin-treated muscles. Innervated hemidiaphragms bound approximately 2.3 x 10(11) molecules of alpha-bungarotoxin; binding sites were restricted to the end-plate region. Neither acute denervation nor acute poisoning with botulinum toxin altered the number or distribution of alpha-bungarotoxin binding sites. In chronically denervated hemidiaphragms, there was an increase in alpha-bungarotoxin binding sites (maximum about 5.7 x 10(12); these sites were distributed across the muscle surface. In chronically poisoned hemidiaphragms, there was also an increase in the number (maximum about 4.7 x 10(12)) and distribution of binding sites. Chronic denervation and chronic botulinum toxin treatment both produced supersensitivity to acetylcholine. At maximal sensitivity, the respective ED50 values were: denervated muscle, 1.1 x 10(-6) M; botulinum toxin-treated muscle, 5.0 x 10(-6) M. The combination of denervation plus botulinum toxin treatment did not have additive or synergistic effects on alpha-bungarotoxin binding (4.9 x 10(12) molecules/hemidiaphragm) or on tissue sensitivity to acetylcholine (ED50 = 2.1 x 10(-6) M). It is concluded that denervation and botulinum toxin have rather similar effects on the number and distribution of acetylcholine receptors in rat hemidiaphragm.
mesh_terms: D000109:Acetylcholine / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D001905:Botulinum Toxins / Q000378:metabolism / Q000494:pharmacology*; D002038:Bungarotoxins / Q000378:metabolism; D003964:Diaphragm / Q000187:drug effects / Q000294:innervation / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009121:Muscle Denervation; D009132:Muscles / Q000187:drug effects / Q000294:innervation* / Q000378:metabolism; D009469:Neuromuscular Junction / Q000187:drug effects; D051381:Rats; D011950:Receptors, Cholinergic / Q000187:drug effects* / Q000378:metabolism; D013997:Time Factors
chemical_list: D002038:Bungarotoxins; D011950:Receptors, Cholinergic; D001905:Botulinum Toxins; D000109:Acetylcholine