1995-Purinergic Receptors and Their Activation by Endogenous Purines.pdf

The Journal of Neuroscience, November 1995, 75(11): 7121-7131
Purinergic Receptors and Their Activation by Endogenous Purines
at Perisynaptic Glial Cells of the Frog Neuromuscular Junction
Richard Robitaille
Centre de Recherche en Sciences Neurologiques and Dkpartement de Physiologie, Universitk de Montreal,
Montreal, Canada H3C 3J7
Glial cells are closely associated with synapses and are et al., 1990). Equipped with this cellular machinery, glial cells
modulated by neurotransmitters released during synaptic closely associated with synapses react to the release of neuro-
transmission. At many synapses, ATP is released during transmitters during synaptic transmission (Chiu and Kriegler.
synaptic transmission and is involved in cell-cell signal- 1994). Synaptic activity generates Ca” responses in work
ing. Since glial cells have purinoceptors, it is possible that of astrocytes in the hippocampus (Dani et al., 1992) and the
ATP mediates synaptic neuron-glia signaling. This work release of neurotransmitters by a single synapse at the frog neu-
aims at determining which types of purinoceptors are pres- romuscular junction is sufficient to induce CaL+ responses in
ent on perisynaptic Schwann cells, the perisynaptic glial perisynaptic glial cells (Jahromi et al., 1992; Reist and Smith,
cells at the frog neuromuscular junction, and test their sen- 1992). These responses are mimicked by local applications of
sitivity to endogenous purines by monitoring the relative neurotransmitters present in synaptic vesicles (Jahromi et al.,
changes of intracellular Ca2+. Local application of ATP in- 1992, 1993).
duced the release of Ca*+ from internal stores. Adenosine In addition to ACh, a large concentration of ATP is also re-
induced Ca2+ responses that were blocked by Al receptor leased during synaptic transmission (Smith, 199 I ; Zimmermann,
antagonists and mimicked by an Al receptor agonist and 1994). More than playing its ub