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M.ª TERESA MIRAS-PORTUGAL Y COLS. ANAL. REAL ACAD. NAC. FARM.

calmoduline kinase II, CaMKII. This enzyme phosphorylates
synapsin allowing the approaching of neurosecretory vesicles to the
docking secretory areas of the presynaptic plasma membrane (61,
77). Figure 6 shows cultured granule neurons loaded with Fura-2
responding to the P2X7 agonist, and to a massive depolarization
induced by K+ ion, to compare the magnitude of both events.

FIGURE 6. ATP effect on cultured granule neurons from mouse cerebellum.
A) Cultured neurons (9 days in vitro) were stimulated with ATP 600 µM for 30
seconds. At the end of the experiment cells were stimulated with KCl to asses its

neuronal nature. B) Microphotographs of the granule neurons at t = 0 s (1);
t = 15 s, during ATP stimulation (2); t = 60 s, before ATP stimulation (3);
t = 140 s, during the masive depolarization induced by KCl (4); t = 200 s, in the
presence of the perfussion medium. The axodendritic fibres that respond to ATP
and to KCl are shown in yellow. The arrow point a responding fibre to ATP.

Scale bar = 5 µm.

Presence and function of P2Y receptors from cultured
cerebellar granule neurons

Cerebellar granule neurons exhibit a great heterogeneity in
nucleotide responses when studies in single cell are carried out.
These responses concern both the ionotropic and metabotropic
responses of P2X and P2Y receptors. These responses all became
modified during the course of granule cells differentiation, not only

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