Stimulation of mouse cultured sympathetic neurons by uracil but not adenine nucleotides

Cultured neurons from the paravertebral sympathetic chain of rats possess e xcitatory P2X as well as excitatory uracil nucleotide-sensitive P2Y recepto rs. Preliminary observations had indicated that the analogous neurons of mi ce lacked P2X receptors. This difference wax now investigated. Thoracolumba r sympathetic neurons from one- to three-day-old mice were cultured for sev en days. When the neurons were preincubated with [H-3]noradrenaline and the n superfused, ATP failed to cause any change in tritium outflow, UTP (3-300 muM) and UDP (30-100 muM), in contrast, caused marked increases, and so di d nicotine (3-100 muM). The effect of UTP was not changed by suramin but ab olished by tetrodotoxin and in the absence of calcium. The effect of nicoti ne was antagonized by hexamethonium and also abolished by tetrodotoxin and in the absence of calcium. Pre-exposure to UDP prevented the effect of UTP. In neurons studied by means of whole-cell patch-clamp techniques under cur rent clamp, ATP lacked any effect. UTP (100 muM), UDP (100 muM) and nicotin e (10 muM) caused depolarization accompanied by action potentials. Pre-expo sure to UDP prevented the effect of UTP. In neurons studied under voltage c lamp, ATP, UTP and UDP failed to cause any detectable current. Nicotine (10 muM), in contrast, elicited inward currents. Neither UTP nor UDP reduced t he M-type potassium outward current. These results demonstrate a pronounced difference between cultured sympathe tic neurons from the mouse and the rat paravertebral chain. Neurons from bo th species possess the nicotinic acetylcholine receptor. Neurons from both species also possess uracil nucleotide-sensitive P2Y receptors which, when activated, mediate depolarization, action potential firing and noradrenalin e release: these effects are not due to inhibition of M-type potassium chan nels. Only the rat but not the mouse neurons, however. possess P2X receptor s which, when activated. mediate cation entry, depolarization, action poten tial generation and transmitter release. The absence of functional P2X rece ptors makes the mouse neurons suitable for further study of the uracil nucl eotide-sensitive P2Y receptors. (C) 2001 IBRO. published by Elsevier Scienc e Ltd. All rights reserved.