Purinergic receptors and synaptic transmission in enteric neurons.

Purines such as ATP and adenosine participate in synaptic transmission in the enteric nervous system as neurotransmitters or neuromodulators. Purinergic receptors are localized on the cell bodies or nerve terminals of different functional classes of enteric neurons and, with other receptors, form unique receptor complements. Activation of purinergic receptors can regulate neuronal activity by depolarization, by regulating intracellular calcium, or by modulating second messenger pathways. Purinergic signaling between enteric neurons plays an important role in regulating specific enteric reflexes and overall gastrointestinal function. In the present article, we review evidence for purine receptors in the enteric nervous system, including P1 (adenosine) receptors and P2 (ATP) receptors. We will explore the role they play in mediating fast and slow synaptic transmission and in presynaptic inhibition of transmission. Finally, we will examine the molecular properties of the native receptors, their signaling mechanisms, and their role in gastrointestinal pathology.