ATP as a neurotransmitter in the brain: Its possibility based upon recent findings

We discuss here possible neurotransmitter roles of extracellular ATP in the central nervous system. Important findings concerning the effects of ATP on central neurons have been made in the last few years. A fast neurotransmitter role of ATP in rat medial habenula reported by Edwards et al. (1992) may be the best example. In rat cultured hippocampal neurons, we have found that ATP evokes postsynaptic currents, and increases the intracellular Ca²⁺ concentration. In addition, ATP also produces a 'long-term potentiation life effect' in these cells. Receptors for ATP are generally divided into two classes: one class is coupled with ion channels and the other class is coupled with GTP-binding proteins. In cultured hippocampal neurons, the GTP-binding protein-coupled receptors are present and promote the inhibition of K⁺ channels. Although the channel-coupled receptors have not been identified in the hippocampal neurons, these channels have been found in nucleus solitarii and locus coeruleus. Several types of ATP receptors have been cloned very recently. These cloned receptors, combined with molecular biological techniques, will allow great progress in this field.