Presynaptic diadenosine polyphosphate receptors: Interaction with other neurotransmitter systems

Diadenosine polyphosphates (Ap(n)A n = 2-6) are natural compounds that can play a neurotransmitter role in the synaptic terminals of the central nervo us system. Microfluorimetric studies of [Ca2+](i) in single synaptic termin als have shown the presence of specific ionotropic receptors for nucleotide s and dinucleotides. These dinucleotide receptors may or may not coexist at the same terminal. Aminergic terminals from rat basal ganglia have been im munologically characterised by the presence of the vesicular monoamine tran sporter 2 after the functional studies. Fifty-eight percent of these termin als respond to nucleotides, and of these, 17% respond only to Ap(5)A. Choli nergic terminals from rat midbrain were immunologically characterised by th e vesicular acetylcholine transporter. Sixty-three percent of these termina ls responded to nucleotides, and of these, 22% responded only to Ap(5)A. Th e presynaptic ionotropic dinucleotide receptors can coexist not only with t he ATP receptors, but also with various subtypes of nicotinic receptors. GA BAergic terminals from rat midbrain were immunologically characterised by t he vesicular inhibitory amino acid transporter. Fifty-nine percent of these terminals responded to nucleotides, and of these, 17% responded only to Ap (5)A. The presynaptic dinucleotide receptors, when stimulated, are able to induce the GABA release from synaptosomal preparations. These data clearly show the broad interaction of nucleotides and dinucleotides with Other neur otransmitter systems. Drug Dev. Res. 52:239-248, 2001. (C) 2001 Wiley-Liss, Inc.