Antisecretory Factor Modulates GABAA Receptor Activity in Neurons
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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 30 s 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 41 pM 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.
KeywordsAntisecretory factor GABAA receptors Cerebellar granule cells Enteric nervous system Central nervous system Patch clamp
Peptides 36–51 of AF sequence
This work was supported by MIUR University of Genoa.
Compliance with Ethical Standards
Experimental procedures and care of the animals were according the EU Parliament and Council of September 22 2010 (2010/63/EU). They were approved by the Italian Ministry of Health (protocol number 2207) according to D.M. 116/1992. All efforts were made in order to minimize animal suffering and the number of animals necessary in order to obtain reliable results.
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