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International audience; The intrinsic primary afferent neurons (IPANs) of the guinea pig enteric nervous system express Na(v)1.9 sodium channels that produce a persistent TTX-resistant current having a low activation threshold and slow gating kinetics. These neurons receive slow EPSPs induced mainly by the activation of neurokinin 3 receptors (NK3r). Here, we demonstrate that senktide, a specific NK3r agonist, potentiates the Na(v)1.9 current (I(Nav1.9)) in IPANs. Using whole-cell patch-clamp recordings from IPANs in duodenum longitudinal muscle/myenteric plexus preparations, we show that short (1-5 s) and long (up to 1 min) applications of senktide, increase the I(Nav1.9) peak current up to 13-fold. The effect, blocked by a NK3r antagonist SB235375 is transient, lasting approximately 2 min and is due to a negative shift of the activation voltage by approximately 20 mV and of fast inactivation by approximately 10 mV. As a consequence, the window current resulting from the product of the activation and fast inactivation curves is shifted and enlarged. The transient effect of senktide is likely to be due to the fast desensitization of NK3r. Protein kinase C (PKC) activation with phorbol or oleoyl acetylglycerol also increases I(Nav1.9), although persistently, by inducing similar voltage-dependent changes. Current-clamp experiments showed that I(Nav1.9) modulation by senktide lowers action potential threshold and increases excitability. The increase in I(Nav1.9) by NK3r activation is also likely to amplify slow EPSPs generated in the IPANs. These changes in excitability potentially have a profound effect on the entire enteric synaptic circuit and ultimately on gut motility and secretion.

International audience; After studying the effects of almitrine, a new kind of ATPase/ATP synthase inhibitor, on two kinds of isolated mammalian mitochondrion, we have observed that: (1) Almitrine inhibits oligomycin-sensitive ATPase; it decreases the ATP/O value of oxidative phosphorylations without any change in the magnitude of delta mu H+. (2) Almitrine increases the mechanistic H+/ATP stoichiometry of ATPase as shown by measuring either (i) the extent of potassium acetate and of potassium phosphate accumulation sustained by ATP utilisation, or (ii) the electrical charge/ATP (K+/ATP) ratio at steady-state of ATPase activity. (3) Rat liver mitochondria are at least 10-times more sensitive to almitrine than beef heart mitochondria. (4) The change in H+/ATP stoichiometry induced by almitrine depends on the magnitude of the flux through ATPase. The inhibitory effect of almitrine on ATPase/ATP synthase complex, as a consequence of such an H+/ATP stoichiometry change, is discussed.