ATP elicits inward currents in isolated vasopressinergic neurohypophysial terminals via P2X2 and P2X3 receptors
Department of Physiology
Medical Subject Headings
Adenosine Triphosphate; Animals; Immunohistochemistry; Male; Pituitary Gland, Posterior; Potassium Channels, Inwardly Rectifying; Rats; Rats, Sprague-Dawley; Receptors, Purinergic P2; Receptors, Purinergic P2X2; Receptors, Purinergic P2X3; Vasopressins
Life Sciences | Medicine and Health Sciences | Neuroscience and Neurobiology
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 microM. 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 > or = 2-methylthioATP > ATP-gamma-S > Bz-Bz-ATP > alpha,beta-methylene-ATP > beta,gamma-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 P2X(2,3,4, and 7), but not P2X6 receptors. Additionally, P2X(2 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 P2X(2 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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Citation: Pflugers Arch. 2005 Sep;450(6):381-9. Epub 2005 Jun 30. Link to article on publisher's site
Pflugers Archiv : European journal of physiology
Knott, Thomas K.; Velazquez-Marrero, Cristina M.; and Lemos, Jose R., "ATP elicits inward currents in isolated vasopressinergic neurohypophysial terminals via P2X2 and P2X3 receptors" (2005). GSBS Student Publications. 1730.