| 1. |
- Bazzurro, V., et al.
(författare)
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Involvement of GABA(A) receptors containing alpha(6) subtypes in antisecretory factor activity on rat cerebellar granule cells studied by two-photon uncaging
- 2022
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Ingår i: European Journal of Neuroscience. - : Wiley. - 0953-816X .- 1460-9568. ; 56:5, s. 4505-4513
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Tidskriftsartikel (refereegranskat)abstract
- The antisecretory factor (AF) is an endogenous protein that counteracts intestinal hypersecretion and various inflammation conditions in vivo. It has been detected in many mammalian tissues and plasma, but its mechanisms of action are largely unknown. To study the pharmacological action of the AF on different GABA(A) receptor populations in cerebellar granule cells, we took advantage of the two-photon uncaging method as this technique allows to stimulate the cell locally in well-identified plasma membrane parts. We compared the electrophysiological response evoked by releasing a caged GABA compound on the soma, the axon initial segment and neurites before and after administering AF-16, a 16 amino acids long peptide obtained from the amino-terminal end of the AF protein. After the treatment with AF-16, we observed peak current increases of varying magnitude depending on the neuronal region. Thus, studying the effects of furosemide and AF-16 on the electrophysiological behaviour of cerebellar granules, we suggest that GABA(A) receptors, containing the alpha(6) subunit, may be specifically involved in the increase of the peak current by AF, and different receptor subtype distribution may be responsible for differences in this increase on the cell.
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| 2. |
- Bazzurro, V., et al.
(författare)
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Antisecretory Factor Modulates GABAA Receptor Activity in Neurons
- 2018
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Ingår i: Journal of Molecular Neuroscience. - : Springer Science and Business Media LLC. - 0895-8696 .- 1559-1166. ; 64:2, s. 312-320
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Tidskriftsartikel (refereegranskat)abstract
- The antisecretory factor is an endogenous protein found in all mammalian tissues investigated so far. It acts by counteracting intestinal hypersecretion and various forms of inflammation, but the detailed mechanism of antisecretory factor (AF) action is unknown. We tested neuronal GABAA receptors by means of AF-16, a potent AF peptide derived from amino acids 36–51 from the NH2 part of AF. Cultured rat cerebellar granule cells were used, and the effects on the GABA-mediated chloride currents were determined by whole-cell patch clamp. Both the neurotransmitter GABA and AF-16 were added by perfusion of the experimental system. A 3-min AF-16 preincubation was more efficacious than 30s in significantly elevating the rapidly desensitizing GABA-activated chloride current. No effect was found on the tonic, slowly desensitizing current. The GABA-activated current increase by AF-16 demonstrated a low k of 41pM with a maximal increase of 37% persisting for some minutes after AF washout, independent from GABA concentration. This indicates an effect on the maximal stimulation (E%Max) excluding an altered affinity between GABA and its receptor. An immunocytochemical fluorescence approach with anti γ2 subunit antibodies demonstrated an increased expression of GABAA receptors. Thus, both the electrophysiological and the immunofluorescence approach indicate an increased appearance of GABAA receptors on the neuronal membrane. The rationale of the experiments was to test the effect of AF on a defined neuronal population of GABAA receptors. The implications of the results on the impact of AF on the enteric nervous system or on brain function are discussed. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.
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| 3. |
- Rapallino, M V, et al.
(författare)
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Antisecretory factor peptide derivatives specifically inhibit [3H]-gamma-amino-butyric acid/36Cl- out-->in permeation across the isolated rabbit Deiters' neuronal membrane.
- 2003
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Ingår i: Acta physiologica Scandinavica. - 0001-6772. ; 179:4, s. 367-71
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Tidskriftsartikel (refereegranskat)abstract
- AIMS: Antisecretory factor (AF) is a 41-kDa protein, its main function being the regulation of intestinal ion/water transport, but it also inhibits chloride and gamma-amino-butyric acid transport across nerve cell membranes. The present experiments were designed to evaluate whether the same AF peptide sequence mediates the permeability effects seen at the nerve cell membrane and in the rat small intestine. METHODS: Four peptides were prepared by the solid phase technique with sequences derived from positions 1-51 of the full-length antisecretory factor AF and tested on nerve cell membranes isolated from rabbit Dieter cells. RESULTS: AF peptides containing the active 36-51 peptide exerted a blocking effect of the out-->in permeation of 36Cl- as well as of [3H]-gamma-amino-butyric acid. The minimal dose causing inhibition, however, varied between 10(-11) m (AF10) and 10(-7) m (AF13). The most potent peptides have been shown previously to be active in inhibiting experimental diarrhoea in vivo in small intestinal ligated loops in rats. The non-active sequence AF23-32 did not inhibit any of the two permeation markers in vitro, a result which supports the lack of activity found also in vivo. CONCLUSION: The results suggest that AF, or AF derivatives, counteract intestinal hypersecretion by blocking anion permeation across large anionic pores. Such a blocking effect could also influence the generation of action potentials in enteric nerve cells controlling the intestinal water and ion transport system.
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