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VOL. 73 (4), 1127-1157, 2007 PHYSIOLOGICAL ROLE OF EXTRACELLULAR...

y nuestro grupo ha demostrado que la mayoría de los receptores P2Y están presen-
tes y son plenamente funcionales en astrocitos en cultivo, donde, dependiendo del
subtipo de receptor, activan una gran variedad de cascadas de señalización.

Palabras clave: receptores ionotrópicos P2X, receptores metabotrópicos P2Y,
sistema nervioso central, ATP, terminales sinápticas, liberación de neurotransmi-
sores.

INTRODUCTION

The wide distribution and the discovery of new and multiple
actions of nucleotides in organs and tissues, through membrane
receptors named P2 purinergic receptors, have aroused a lot of
interest in investigating their cellular biology, the type of
dysfunctions associated with the excess or defect of nucleotide
signalling, and the search and design for reliable agonists and
antagonists that can be used in pharmacology. In the last two years
we have assisted to the growing progress in the number of
publications related to nucleotide signalling and its physio-
pathological implications, which gives evidence of its therapeutic
potential in a near future. Between the increasing numbers of
revisions, we have selected those written by Professor G. Burnstock,
by their historical meaning and seminal contributions (1-3). The
prestigious journal Trends in Pharmacological Sciences, com-
memorated the 75th anniversary of the British Pharmacological
Society foundation with the publication of a special volume, in which
the revision of Burnstock entitled «ATP as a neurotransmitter» (4),
is included as one of the 6 most relevant and historical revisions. 36
years ago, Pharmacological Reviews published an article entitled
«Purinergic Nerves» (5) that first laid the foundations of purinergic
neurotransmission, but that finding was scarcely attractive to the
scientific community at that time.

The extracellular role of ATP, or any other nucleotide, requires
the presence of this compound outside the cell. In this way, the
presence of ATP and other nucleotides and dinucleotides in a large
variety of storage and secretory vesicles, such as the cholinergic and
aminergic ones, from neural or neuro-endocrine tissues, or the ones
from platelets and mastocytes, suggested an extracellular role, as co-
transmitter, or extracellular functions for nucleotides (6). The

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