Abstract
We have studied the postjunctional characteristics of motor endplates in the extensor digitorum longus (EDL) and soleus muscles of the rat. At voltage clamped endplates, equilibrium interactions between acetylcholine (ACh) and the ACh receptor were determined from the dose-response curves obtained by quantitative ionophoresis of ACh. These results showed that the maximum ACh induced conductance change per unit endplate surface,g max, was 21.8±0.9 nS/μm2 in EDL and 8.2±0.9 nS/μm2 in soleus, the apparent dissociation constant,K, was 65.9±4.3 μM in EDL and 43.5±3.3 μM in soleus, and the Hill-coefficient,n H, was 2.3±0.1 in EDL and 2.2±0.1 in soleus.
Single channel characteristics were derived from analysis of the ACh-induced endplate current noise. The results showed that at room temperature the mean conductance of the single channel, γ, was 24.6±1.2 pS in EDL and 23.9±1.2 pS in soleus, and the mean life time of the channel, τ, was 0.80±0.05 ms in EDL and 0.71±0.03 ms in soleus.
Of all the properties studied, the maximum conductance per unit endplate surface,g max, was significantly smaller at the soleus endplate than at the EDL endplate. The calculated density of functional ACh receptors was 62% less, and the total number of the functional ACh receptors was 60% less at the soleus endplates than at the EDL endplates. These results suggest that the soleus has a lower margin of safety for neuromuscular transmission than the EDL.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Albuquerque EX, McIsaac RJ (1970) Fast and slow mammalian muscles after denervation. Exp Neurol 26:183–202
Albuquerque EX, Thesleff S (1968) A comparative study of membrane properties of innervated and chronically fast and slow skeletal muscles of the rat. Acta Physiol Scand 73:471–480
Albuquerque EX, Barnard EA, Porter CW, Warnick JE (1974) The density of acetylcholine receptors and their sensitivity in the postsynaptic membrane of muscle endplates. Proc Natl Acad Sci USA 71:2818–2822
Anderson CR, Stevens CF (1973) Voltage clamp analysis of acetylcholine produced endplate current fluctuations at frog neuromuscular junction. J Physiol 235:655–691
Anderson MJ, Cohen MW (1974) Fluorescent staining of acetylcholine receptors in vertebrate skeletal muscle. J Physiol 237:385–400
Ariano MA, Armstrong RB, Edgerton VR (1973) Hindlimb muscle fiber populations of five mammals. J Histochem Cytochem 21:51–55
Barany M, Barany K, Rickard T, Volpe A (1965) Myosin of fast and slow muscles of the rabbit. Arch Biochem Biophys 109:185–191
Barnard EA, Rymaszewska T, Wieckowski J (1971) Cholinesterase at individual neuromuscular junctions. In: Triggle DJ, Moran JF, Barnard EA (eds) Cholinergic ligand interactions. Academic Press, New York, pp 175–200
Close R (1964) Dynamic properties of fast and slow skeletal muscles of the rat during development. J Physiol 173:74–95
Dreyer F, Mueller KD, Peper K, Sterz R (1976a) The M. omohyoideus of the mouse as a convenient mammalian muscle preparation: a study of junctional and extrajunctional acetylcholine receptors by noise analysis and cooperativity. Pflügers Arch 367:115–122
Dreyer F, Walther Chr, Peper K (1976b) Junctional and extrajunctional receptors in normal and denervated frog muscle fibers. Pflügers Arch 366:1–9
Dreyer F, Peper K, Sterz R (1978) Determination of dose-response curves by quantitative ionophoresis at the frog neuromuscular junction. J Physiol 281:395–419
Eccles LC, Eccles RM, Lundberg A (1958) The action potentials of the alpha motoneurons supplying fast and slow muscles. J Physiol 142:275–291
Ellisman MH, Rash JE, Staehlin LA, Porter KR (1976) Studies of excitable membranes. II. A comparison of specializations at neuromuscular junctions and non-junctional sarcolemmas of mammalian fast and slow twitch muscle fibres. J Cell Biol 68:752–774
Fambrough DM (1979) Control of acetylcholine receptors in skeletal muscle. Physiol Rev 59:165–227
Fertuck HC, Salpeter MM (1974) Localization of acetylcholine receptor by125I-labelled bungarotoxin at mouse endplates. Proc Natl Acad Sci USA 71:1376–1378
Goldspink DF, Harris JB, Park DC, Parsons NE, Pennington RJ (1971) Quantitative enzyme studies in deneravated extensor digitorum longus and soleus of rats. J Biochem 2:427–433
Guth L, Samaha FJ (1969) Qualitative differences between actomyosin ATPase of slow and fast mammalian muscle. Exp Neurol 25:138–152
Hohlfeld R, Sterz R, Kalies I, Peper K, Wekerle H (1981) Neuromuscular transmission in experimental autoimmune myasthenia gravis (EAMG). Pflügers Arch 390:156–160
Karnovsky MJ, Roots L (1964) A direct coloring thiocholine method for cholinesterase. J Histochem Cytochem 12:219–221
Kaul M, Hammer H, Sterz R, Peper K (1982) Immunofluorescence of the acetylcholine receptor in endplates. Pflügers Arch 394 (Suppl): R51
McArdle JJ, Albuquerque EX (1973) A study of the reinnervation of fast and slow mammalian muscles. J Gen Physiol 61:1–23
Miledi R, Zelena J (1966) Sensitivity to acetylcholine in rat slow muscles. Nature 210:855–856
Nachmias VT, Padykula HA (1958) A histochemical study of normal and denervated and white muscle of the rat. J Biophys Biochem Cytol 4:47–57
Paton WDM, Zaimis EJ (1951) The action ofd-tubocurarine and of decamethonium on respiratory and other muscles in the cat. J Physiol 112:311–331
Peper K, Sterz R, Bradley RJ (1980) Effects of drugs and antibodies on the postsynaptic membrane of the neuromuscular junction. Ann NY Acad Sci 377:519–543
Peper K, Bradley RJ, Dreyer F (1982) The acetylcholine receptor at the neuromuscular junction. Physiol Rev 62:1271–1340
Robbins N, Olek A, Kelly SS, Takach P, Christopher M (1980) Quantitative study of motor endplates in muscle fibers dissociated by a simple procedure. Proc R Soc Lond B 209:555–562
Stein JM, Padykula HA (1962) Histochemical classification of individual skeletal muscle fibers of the rat. Am J Anat 110:103–115
Sterz R, Pagala MKD, Peper K (1982) Post-junctional properties of motor endplates in mammalian fast and slow muscles. Fed Proc 41:8680
Tonge DA (1974) Chronic effects of botulinum toxin on neuromuscular transmission and sensitivity to acetylcholine in slow and fast skeletal muscle of the mouse. J Physiol 241:127–139
Yonemura K (1967) Resting and action potentials in red and white muscle of the rat. Jpn J Physiol 17:708
Author information
Authors and Affiliations
Additional information
This work was supported by the Deutsche Forschungsgemeinschaft, SFB 38, project N
Rights and permissions
About this article
Cite this article
Sterz, R., Pagala, M. & Peper, K. Postjunctional characteristics of the endplates in mammalian fast and slow muscles. Pflügers Arch. 398, 48–54 (1983). https://doi.org/10.1007/BF00584712
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00584712