Physostigmine and Neuromuscular Transmissiona

Maelicke, Alfred; Coban, Thomas; Schrattenholz, André; Schröder, Bernd; Reinhardt-Maelicke, Sigrid; Storch, Alexander; Godovac‐Zimmermann, Jasminka; Methfessel, Christoph; Pereira, Edna F. R.; Albuquerque, Edson X.

doi:10.1111/j.1749-6632.1993.tb22880.x

Cited by 17 publications

(8 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Similarly, patch-clamp studies employing reconstituted giant vesicles of Torpedo nAChR [23] have fully confirmed the results reported for physostigmine-induced ion flux into Torpedo membrane vesicles [20, 211. In this study, we demonstrate that ['Hlphysostigmine can be activated by ultraviolet irradiation to react covalently with its binding site(s) on the membrane-bound Torpedo nAChR. Further analysis showed that predominantly the a polypep-tide is labeled by the radioactive ligand, with most, if not all, of the specific label associated with Lys125.…”

supporting

confidence: 77%

“…Recent electrophysiological studies employing nAChR preparations from mammalian muscle and central nervous tissue, have shown that the channel-activating action of physostigmine and the unusual pharmacology of the effect, are not limited to Torpedo or frog muscle nAChR but appear to be a general property of nicotinic receptors 122, 231. Similarly, patch-clamp studies employing reconstituted giant vesicles of Torpedo nAChR [23] have fully confirmed the results reported for physostigmine-induced ion flux into Torpedo membrane vesicles [20, 211. In this study, we demonstrate that ['Hlphysostigmine can be activated by ultraviolet irradiation to react covalently with its binding site(s) on the membrane-bound Torpedo nAChR. Further analysis showed that predominantly the a polypep-tide is labeled by the radioactive ligand, with most, if not all, of the specific label associated with Lys125.…”

supporting

confidence: 77%

“…Particularly significant examples are cultured hippocampal neurons [22] and fibroblasts stably transfected with a4fl chick neuronal nAChR (unpublished results). From these results, neuronal nAChR appears to be much more sensitive to physostigmine and related compounds than neuromuscular or electrocyte receptors [23]. In noteworthy contrast to the M1O fibroblast cell line expressing the major brain nicotinic receptor, Xenopus oocytes, transiently expressing functional Torpedo or rat muscle receptors, did respond to physostigmine by means of receptor-channel activation (unpublished results).…”

Section: Discussionmentioning

confidence: 89%

See 2 more Smart Citations

Photoaffinity labeling of Torpedo acetylcholine receptor by physostigmine

Schrattenholz¹,

Godovac‐Zimmermann²,

Schäfer

et al. 1993

European Journal of Biochemistry

Self Cite

View full text Add to dashboard Cite

The plant alkaloid physostigmine, an established anti-cholinesterase agent of the carbamate type, has recently been shown to bind to the nicotinic acetylcholine receptor from Torpedo marmorutu electrocytes [Okonjo, K. O., Kuhlmann, J. & Maelicke, A. (1991) Eur. J. Biochem. 200, Pharmacological studies of physostigmine-induced ion flux into nicotinic-acetylcholine-receptorrich membrane vesicles, indicated distinct binding sites for physostigmine and acetylcholine. As shown in this study by photoaffinity labeling with [phenyl-(n)-'HI( -)physostigmine, the physostigmine-binding site is located within the same subunit (a polypeptide) of the receptor as the acetylcholine-binding site. Using a variety of proteolytic cleavage conditions for the purified a polypeptide, several ['Hlphysostigmine-labeled peptides were isolated and sequenced. From the radioactivity released in the course of the Edman degradations of the labeled peptides, it was found that the label was associated in all cases with Lys125. These results identify a novel ligand-binding site for the Torpedo nicotinic acetylcholine receptor that is different in location from binding sites identified previously for acetylcholine, its established agonists and antagonists, and di.rect channel blockers.(-)Physostigmine (eserine), the major alkaloid of the calabar bean Physostigma venenosum Balfour [l], is a slowly reversible inhibitor of acetylcholine esterase (AChE), acting by carbamoylation of the active serine residue within the 'esteratic site' of the enzyme [2, 31. This ancient drug [4] continues to be widely used as a diagnostic aid, as an analgesic, in the recovery from anaesthesia, in the treatment of some types of psychosis, for the treatment of alcohol intoxication and glaucoma, and, most recently, for the treatment of acute brain hypoxia IS] and Alzheimer's disease [6, 71. Since physostigmine readily penetrates the bloodhrain barrier, it mainly acts in the braidcentral nervous system. In spite of its wide-spread medical applications and long use in research, however, many of its actions are not yet thoroughly understood, including those at cholinergic and serotonergic synapses [8-141. Evidence has been assembled over the past few years suggesting that, in addition to acting as an inhibitor of AChE, the drug directly interacts with both muscarinic (mAChR) and nicotinic (nAChR) acetylcholine receptors [ 10-141.Studying frog muscle nAChR, we have recently demonstrated that physostigmine, below 1 pM, induces single-channel currents with amplitudes and open-time characteristics typical for the nAChR channel [12,. At higher con- [20, 211. Surprisingly, the direct action of physostigmine at the Torpedo nAChR was unaffected by the presence of saturating concentrations of acetylcholine antagonists, including a bungarotoxin and D-tubocurarine 1201, or when nAChR was desensitized by elevated concentrations of acetylcholine [21]. In addition, we established that two monoclonal antibodies raised against nAChR could competitively inhibit the binding of physostigmi...

show abstract

supporting

confidence: 77%

supporting

confidence: 77%

Section: Discussionmentioning

confidence: 89%

See 1 more Smart Citation

Photoaffinity labeling of Torpedo acetylcholine receptor by physostigmine

Schrattenholz¹,

Godovac‐Zimmermann²,

Schäfer

et al. 1993

European Journal of Biochemistry

Self Cite

View full text Add to dashboard Cite

show abstract

“…Apart from inhibiting acetyl‐cholinesterases, high concentrations of physostigmine and tacrine interact directly with neuronal nAChRs (Perry et al, 1988). Ion flux studies on Torpedo electrocyte membrane vesicles (Okonjo et al, 1991) and single channel patch‐clamp studies on rat myoballs (Maelicke et al, 1993), cultured rat hippocampal neurons (Pereira et al, 1993), mouse fibroblast (M10) cells stably transfected with chicken α4β2 nAChRs (Pereira et al, 1994), and rat pheochromocytoma (PC12) cells (Storch et al, 1995) have shown that galanthamine and physostigmine activate nAChR channels. The physostigmine‐ and galanthamine‐activated single‐channel events are blocked by a monoclonal antibody (FK1) raised against the rat muscle nAChR but not by competitive nAChR antagonists.…”

mentioning

confidence: 99%

Competitive Potentiation of Acetylcholine Effects on Neuronal Nicotinic Receptors by Acetylcholinesterase‐Inhibiting Drugs

Zwart¹,

Kleef²,

Gotti³

et al. 2000

Journal of Neurochemistry

View full text Add to dashboard Cite

Abstract:The effects of the acetylcholinesterase inhibitors physostigmine and tacrine on ␣4␤2 and ␣4␤4 subtypes of neuronal nicotinic acetylcholine (ACh) receptors, expressed in Xenopus laevis oocytes, have been investigated. In voltage-clamp experiments low concentrations of physostigmine and tacrine potentiate ion currents induced by low concentrations of ACh, whereas at high concentrations they inhibit ACh-induced ion currents. These dual effects result in bell-shaped concentrationeffect curves. Physostigmine and tacrine, by themselves, do not act as nicotinic receptor agonists. The larger potentiation is observed with 10 M physostigmine on ␣4␤4 nicotinic receptors and amounts to 70% at 1 M ACh. The mechanism underlying the effects of physostigmine on ␣4␤4 ACh receptors has been investigated in detail. Potentiation of ACh-induced ion current by low concentrations of physostigmine is surmounted at elevated concentrations of ACh, indicating that this is a competitive effect. Conversely, inhibition of ACh-induced ion current by high concentrations of physostigmine is not surmounted at high concentrations of ACh, and this effect appears mainly due to noncompetitive, voltage-dependent ion channel block. Radioligand binding experiments demonstrating displacement of the nicotinic receptor agonist 125 I-epibatidine from its recognition sites on ␣4␤4 ACh receptors by physostigmine confirm that physostigmine is a competitive ligand at these receptors. A twosite equilibrium receptor occupation model, combined with noncompetitive ion channel block, accounts for the dual effects of physostigmine and tacrine on ACh-induced ion currents. It is concluded that these acetylcholinesterase-inhibiting drugs interact with the ACh recognition sites and are coagonists of ACh on ␣4-containing nicotinic ACh receptors. Key Words: Neuronal nicotinic acetylcholine receptor-Acetylcholinesterase inhibitorTacrine -Physostigmine -Two-site receptor occupation model-Xenopus oocyte.

show abstract

“…36,37 Exciting new studies in the 1980s showed that carbamate ChEIs act in quite diverse ways on the postsynaptic regions of both neuronal and neuromuscular cholinergic synapses. 23,25,31,33 They interact with the nicotinic acetylcholine receptor (nAChR) macromolecule as a weak agonist, 1,23,25,30,33 and as a modulator inducing, at high concentrations, the formation of desensitized receptor-complex intermediates. 1,33 They also act as direct channel blockers 33,40 and, at a high concentration, inhibit the binding of agonists to nAChRs.…”

mentioning

confidence: 99%