Abstract
Effects of extracellular adenosine tri-phosphate (ATP) on ionic currents were investigated using the perforated-patch whole-cell recording technique on isolated terminals of the Hypothalamic Neurohypophysial System (HNS). ATP induced a current response in 70% of these isolated terminals. This inwardly-rectifying, inactivating current had an apparent reversal near 0 mV and was dose-dependent on ATP with an EC50=9.6±1.0 μM. In addition, current amplitudes measured at maximal ATP concentrations and optimum holding potentials had a current density of 70.8 pA pF−1 and were greatly inhibited by suramin and PPADS. Different purinergic receptor agonists were tested, with the following efficacy: ATP ≥ 2-methylthioATP > ATP-γ-S > Bz-Bz-ATP > α,β-methylene-ATP > β,γ-methylene-ATP. However, UTP and ADP were ineffective. These data suggest the involvement of a P2X purinergic receptor in the ATP-induced responses. Immunocytochemical labeling in vasopressinergic terminals indicates the existence of P2X2,3,4, and 7, but not P2X6 receptors. Additionally, P2X2 and 3 were not found in terminals which labeled for oxytocin. In summary, the EC50, decay, inactivation, and pharmacology indicate that a functional mixture of P2X2 and 3 homomeric receptors mediate the majority of the ATP responses in vasopressinergic HNS terminals. We speculate that the characteristics of these types of receptors reflect the function of co-released ATP in the terminal compartment of these and other CNS neurons.
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References
Bean BP (1992) Pharmacology and electrophysiology of ATP-activated ion channels. TIPS 13:87–90
Ben-Barak Y, Russell JT, Whitnall MH, Ozato K, Gainer H (1985) Neurophysin in the hypothalamo-neurohypophysial system: 1. Production and characterization of monoclonal antibodies. J Neurosci 5:81–97
Bicknell RJ, Leng G (1981) Relative efficiency of neural firing patterns for vasopressin release in vitro. Neuroendocrinology 33:295–299
Buell G, Lewis C, Collo G, North RA, Surprenant A (1996) An antagonist-insensitive P2X receptor expressed in epithelia and brain. EMBO J 15:55–62
Cazalis M, Dayanithi G, Nordmann JJ (1985) The role of patterned burst and interburst interval on the excitation-coupling mechanism in the isolated rat neural lobe. J Physiol 369:45–60
Currie KP, Fox AP (1996) ATP serves as a negative feedback inhibitor of voltage-gated Ca2+ channel currents in cultured bovine adrenal chromaffin cells. Neuron 16:1027–1036
Dudek RE, Hatton GI, MacVicar BA (1980) Intracellular recording from paraventricular nucleus in slices of rat hypothalamus. J Physiol 301:101–114
Edwards FA, Gibb AJ (1993) ATP-a fast neurotransmitter. FEBS Lett 325:86–89
Evans RJ, Derkach V, Suprenant A (1992) ATP mediates fast synaptic transmission in mammalian neurons. Nature 357:503–505
Fisher TE, Carrion-Vasquez M, Fernandez JM (2000)Intracellular Ca2+ channel immunoreactivity in neuroendocrine axon terminals. FEBS Lett 24153:1–8
Gu JG, MacDermott AB (1997) Activation of ATP P2X receptors elicits glutamate release from sensory neuron synapses. Nature 389:749–753
Hugel S, Schlichter R (2000) Presynaptic P2X receptors facilitate inhibitory GABAergic transmission between cultured rat spinal cord dorsal horn neurons. J Neurosci 20(6):2121–2130
Inoue K, Nakazawa K (1992) ATP receptor-operated Ca2+ -influx and catecholamine release from neuronal cells. News Physiol Sci 7:56–59
Knott TK, Dopico AM, Dayanithi G, Lemos JR, Treistman SN (2002) Integrated channel plasticity contributes to alcohol tolerance in isolated neurohypophysial terminals. Molec Pharmacol 4(7):1077–1083
Knott TK, Hussy N, Lemos JR (2004) Exogenous adenosine triphosphate (ATP) elicits inward currents via different P2X receptors in hypothalamic neurohypophysial system terminals vs. somata. Soc Neurosci Abstr 30:958.6
Kristal OA, Marchenko SM, Pidoplichko VI (1983) Receptor for ATP in the membrane of mammalian sensory neurons. Neurosci Lett 35:41–45
Lemos JR (2002) Magnocellular neurons. Encyc Life Sci A176:1–5
Lemos JR, Adams WB, Novak-Hofer I, Benson JA, Levitan IB (1986) Regulation of neuronal activity by protein phosphorylation. In: Alkon D and Woody A (eds) Neural mechanisms of conditioning. Plenum, New York, pp 397–420
Lemos JR, Nordmann JJ (1986) Ionic channels and hormone release from peptidergic nerve terminals. J Exp Biol 124:53–72
Lemos JR, Wang G (2000) Excitatory versus inhibitory modulation by ATP of neurohypophysial terminal activity in the rat. Exp Physiol 85S:67–85
Loesch A, Miah S, Burnstock G (1999) Ultrastructural localization of ATP-gated P2X2 receptor immunoreactivity in the rat hypothalamo-neurohypophysial system. J Neurocyt 28:495–504
North RA (2002) Molecular physiology of P2X receptors. Physiol Rev 82, 1013–1067
Nowycky MC, Seward EP, Chernevskaya NI (1998) Excitation-secretion coupling in mammalian neurohypophysial nerve terminals. Cell Mol Neurobiol 18:65–80
Poulain DA, Wakerly JB (1982) Electrophysiology of hypothalamic magnocellular neurones secreting oxytocin and vasopressin. Neuroscience 7:773–808
Shibuya I, Tanaka K, Hattori Y, Uezono Y, Harayama N, Noguchi J, Ueta Y, Izumi F, Yamashita H (1999)Evidence that multiple P2X purinoceptors are functionally expressed in rat supraoptic neurons. J Physiol 514(2):351–367
Shigetomi E, Kato F (2004) Action potential-independent release of glutamate by Ca2+ entry through presynaptic P2X receptors elicits postsynaptic firing in the brainstem autonomic network. J Neurosci 24(12):3125–3135
Soldo BL, Giovannucci DR, Stuenkel EL, Moises HC (2004) Ca2+ and frequency dependence of exocytosis in isolated somata of magnocellular supraoptic neurones of the rat hypothalamus. J Physiol 555(3):699–711
Sperlagh B, Mergl Z, Juranyi Z, Visi ES, Makara GB (1999) Local regulation of vasopressin and oxytocin secretion by extracellular ATP in the isolated posterior lobe of the rat hypophysis. J Endocrinol 160:343–350
Stuenkel EL (1985) Simultaneous monitoring of electrical and secretory activity in peptidergic neurosecretory terminals of the crab. J Physiol 359:163–187
Sun XP, Stanley EF (1996) An ATP-activated, ligand-gated ion channel on a cholinergic presynaptic nerve terminal. Proc Natl Acad Sci USA 93:1859–1863
Tomic M, Jobin RM, Vergara LA, Stojilkovic SS (1996) Expression of purinergic receptor channels and their role in calcium signaling and hormone release in pituitary gonadotrophs. J Biol Chem 271:21200–21208
Troadec JD (1998) Régulation du couplage stimulus-sécrétion par l’ATP extracellulaire dans la neurohypophyse de rat. Thése PhD University of Nice-Sophia Antipolis
Troadec JD, Thirion S, Nicaise G, Lemos JR, Dayanithi G (1998) ATP-evoked increases in [Ca2+]i and peptide release from rat isolated neurohypophysial terminals via a P2×2 purinoceptor. J Physiol 511:89–103
Zimmermann H (1994) Signalling via ATP in the nervous system. TINS 17:420–426
Acknowledgements
This work was supported by NIH grant NS29470. Thanks to Nicolas Hussy for helpful discussions and Catherine Wanko for technical assistance.
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Knott, T.K., Velázquez-Marrero, C. & Lemos, J.R. ATP elicits inward currents in isolated vasopressinergic neurohypophysial terminals via P2X2 and P2X3 receptors. Pflugers Arch - Eur J Physiol 450, 381–389 (2005). https://doi.org/10.1007/s00424-005-1471-x
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DOI: https://doi.org/10.1007/s00424-005-1471-x