P2X2 and P2Y1 immunofluorescence in rat neostriatal medium-spiny projection neurones and cholinergic interneurones is not linked to respective purinergic receptor function

摘要

class="enumerated" style="list-style-type:decimal">The presence of ionotropic P2X receptors, targets of ATP in fast synaptic transmission, as well as metabotropic P2Y receptors, known to activate K⁺ currents in cultured neostriatal neurones, was investigated in medium-spiny neurones and cholinergic interneurones contained in neostriatal brain slices from 5–26-day-old rats.In these cells, adenosine-5′-triphosphate (ATP) (100–1000 μM), 2-methylthioadenosine-5′-triphosphate (2MeSATP), α,β-methyleneadenosine-5′-triphosphate (α,βmeATP, 30–300 μM, each) and adenosine-5′-O-(3-thiotriphosphate (ATPγS) (100 μM) failed to evoke P2X receptor currents even when 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 0.1 μM), apyrase (10 U ml⁻¹) or intracellular Cs⁺ was used to prevent occluding effects of the ATP breakdown product adenosine, desensitisation of P2X receptors by endogenous ATP and an interference with the activation of K⁺ channels, respectively. P2X receptor agonists were also ineffective in outside-out patches withdrawn from the brain slice tissue. Muscimol (10 μM) evoked GABAA receptor-mediated currents under all these conditions.When used as a control, locus coeruleus neurones responded with P2X receptor-mediated currents to ATP (300 μM), 2MeSATP and α,βmeATP (100 μM, each).ATP and adenosine-5′-diphosphate (ADP) (100 μM, each) did not activate K⁺ currents in the neostriatal neurones.Despite the observed lack of function, P2X2 and P2Y1 immunofluorescence was found in roughly 50% of the medium-spiny neurones and cholinergic interneurones.A role of ATP in synaptic transmission to striatal medium-spiny neurones and cholinergic interneurones appears unlikely, however, the otherwise silent P2X and P2Y receptors may gain functionality under certain yet unknown conditions.