On the oscillatory decay of the myotonic action of 9 anthroic acid. Influence of cholinesterase inhibition
article
The effects of the myotonic agent, 9-anthroic acid (ANCA), and the acetylcholinesterase (AChE) inhibitor, soman, on the isolated phrenic nerve-diaphragm preparation of the rat were studied. ANCA induced after-contractions which followed the twitches evoked by either direct or indirect stimulation. In the intermittently stimulated muscle the height of the after-contractions decreased rather rapidly and in an oscillatory fashion. The maximum height of each after-contraction was attained after the twitch had reached its peak. AChE inhibition changed the shape of these after-contractions in the indirectly, but not in the directly stimulated diaphragm. After AChE inhibition, the after-contractions decreased more slowly and in a non-oscillatory manner. Similar phenomena were observed in vivo in the gastrocnemius-soleus muscles. The effects of ANCA in the AChE-inhibited and in the non-inhibited diaphragm could be mimicked by incubation in low chloride media. Addition of ouabain to the non-inhibited diaphragm treated with ANCA, caused an immediate and striking enhancement followed by a rapid loss of the after-contractions, whereas the twitches remained fairly constant. In the AChE-inhibited diaphragm treated with ANCA, ouabain caused no increase but only a rapid and complete decay of the after-contractions with a decrease of the twitches. It is suggested that after inhibition of the AChE in the ANCA-treated muscle fibre, the site of initiation of the repetitive action potentials which cause the after-contractions shifts from the transverse tubular system to the motor end-plate. Moreover, it is suggested that the sodium pump is involved in the gradual decay of the myotonic action of ANCA. Chemicals/CAS: 9 anthroic acid, 723-62-6; acetylcholinesterase, 9000-81-1; curare, 8063-06-7; ouabain, 11018-89-6, 630-60-4; soman, 96-64-0; Anthracenes; Calcium, 7440-70-2; Carboxylic Acids; Chlorides; Cholinesterase Inhibitors; Magnesium, 7439-95-4; Ouabain, 630-60-4; Potassium, 7440-09-7; Sodium, 7440-23-5; Soman, 96-64-0
Topics
9 Anthroic acidAcetylcholinesteraseAdenosine triphosphatase (potassium sodium)Cholinesterase inhibitorCurareOuabainSomanIn vitro studyMuscle contractionMyotoniaRatTheoretical studyAnimalAnthracenesCalciumCarboxylic AcidsChloridesCholinesterase InhibitorsDiaphragmDrug InteractionsElectric StimulationIn VitroMagnesiumMaleMotor EndplateMuscle ContractionNeuromuscular JunctionOuabainPotassiumRatsSodiumSoman
TNO Identifier
228259
ISSN
00142999
Source
European Journal of Pharmacology, 42(3), pp. 207-216.
Pages
207-216
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