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VOL. 76 (1), 3-22, 2010 CROSS-TALK BETWEEN GLUTAMATE AND NUCLEOTIDE...

glutamato son capaces de modular las respuestas a nucleótidos en
neuronas granulares de cerebelo.

Palabras clave: Interacción; Receptores P2; Receptores de Glu-
tamato; Calcio-calmodulina-quinasa II.

1. INTRODUCTION

Cerebellar granule neurons have a critical role in cerebellar
function coordinating afferent input to and motor output from the
cerebellum. Thus, granule cells receive excitatory glutamatergic
contacts from mossy fibres and they, in turn, contact synaptically with
the dendrites of Purkinje neurons via parallel fibres. Excitatory
synaptic transmission between mossy fibres and granule neurons
is mediated by L-Glu (1). The actions of L-Glu are mediated by a
group of receptors named glutamate receptors which have been
subclassified into ionotropic glutamate receptors (NMDA and non
NMDA) and metabotropic glutamate receptors that includes Group I,
II and III. Cerebellar granule cells express both Ca2+ permeable NMDA
and non-NMDA glutamate receptors (2). Furthermore, group I
metabotropic glutamate receptor involved in the glutamate activation
of phospholipase C (PLC) and Ca2+ mobilization have also been
described in granule cells growth in vitro (3). Recently, we have shown
the presence and expression of functional nucleotide receptors in
highly purified cultures of cerebellar granule neurons (4-8). The
family of nucleotide receptor includes ionotropic receptors, P2X,
which form ligand gated cation channels and mediate fast excitatory
responses; and metabotropic nucleotide receptors, P2Y, which belong
to the G-protein-coupled receptor superfamily (9, 10).

As our understanding of cellular signalling pathways has
advanced, it has became increasingly apparent that, far from
regulating linear transduction pathways, receptor activation can
result in much more complex patterns of signalling within cells.
Thus, the activation of neurotransmitter receptors by their own
transmitter has been shown to be modulated by distinct receptors
when they are also activated by their own transmitter. This
mechanism, generally termed cross talk, provides a fast and efficient

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