title: Regulation of the mechanosensitive cation channels by ATP and cAMP in leech neurons.
abstract: Single-channel recordings were used to study the modulation of stretch-activated channels (SACs) by intracellular adenosine nucleotides in identified leech neurons. These channels exhibited two activity modes, spike-like (SL) and multiconductance (MC), displaying different polymodal activation. In the absence of mechanical stimulation, internal perfusion of excised patches with ATP induced robust and reversible activation of the MC but not of the SL mode. The ATP effect on channel activity was dose-dependent within a range of 1 microM-1 mM and was induced at different values of intracellular pH and Ca2+. The non-hydrolyzable ATP analog AMP-PNP, ATP without Mg2+ or ADP also effectively enhanced MC activity. Adenosine mimicked the effect of its nucleotides. At negative membrane potentials, both ATP and adenosine activated the channel. Moreover, ATP but not adenosine induced a flickering block. Addition of cAMP during maximal ATP activation completely and reversibly inhibited the channel, with activation and deactivation times of minutes. However, cAMP alone only induced a weak and rapid channel activation, without inhibitory effects. The expression of these channels in the growth cones of leech neurons, their permeability to Ca2+ and their sensitivity to intracellular cAMP are consistent with a role in the Ca2+ oscillations associated with cell growth.
authors.affiliation: Dipartimento di Fisiologia e Biochimica G. Moruzzi, Università di Pisa, Via S. Zeno 31, 56127, Pisa, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Barsanti
authors.forename: Monica
authors.initials: M
authors.lastname: Pellegrini
authors.forename: Mario
authors.initials: M
authors.lastname: Pellegrino
mesh_terms: D000255:Adenosine Triphosphate / Q000502:physiology*; D000818:Animals; D002412:Cations; D000242:Cyclic AMP / Q000502:physiology*; D007473:Ion Channels / Q000502:physiology*; D007865:Leeches; D018408:Patch-Clamp Techniques
chemical_list: D002412:Cations; D007473:Ion Channels; D000255:Adenosine Triphosphate; D000242:Cyclic AMP