Adenosine triphosphate and diadenosine pentaphosphate induce [Ca2+](i) increase rat basal ganglia aminergic terminals

Synaptosomal preparations from rat midbrain exhibit specific responses to b oth ATP and Ap(5)A, which stimulate a [Ca2+](i) increase in the presynaptic terminals via specific ionotropic receptors, termed P2X, and diadenosine p olyphosphate receptors. Aminergic terminals from rat brain basal ganglia we re characterized by immunocolocalization of synaptophysin and the vesicular monoamine transporter VMAT2 and represent 29% of the total. These aminergi c terminals respond to ATP and/or Ap(5)A with an increase in the intrasynap tosomal calcium concentration as measured by a microfluorimetric technique. This technique, which allows single synaptic terminals to be studied, show ed that roughly 8.2% +/- 1.6% of the aminergic terminals respond to ATP, 16 .9% +/- 1.3% respond to Ap(5)A, 32.6% +/- 0.8% to both, and 42.3% +/- 1.5% of them have no response. Immunological studies performed with antibodies a gainst ionotropic ATP receptor subunits showed positive labelling with anti -P2X(3) antibodies in 39% of the terminals. However, colocalization studies of VMAT and P2X(3) receptor subunit indicate that only 25% of the aminergi c terminals also contain this receptor subtype. These results demonstrate t hat the aminergic terminals from the rat brain basal ganglia are to a large extent under the modulation of presynaptic nucleotide and dinucleotide rec eptors, J, Neurosci. Res. 64:174-182, 2001, (C) 2001 Wiley-Liss, Inc.