Purinergic modulation of the primary afferent to second-order transmission in the dorsal vagal complex: molecular to physiological evidence

Abstract

The visceral afferent fibers arising from various cervico-abdominal receptors form the first intracerebral synapse in the dorsal vagal complex composed of the nucleus of the solitary tract (NTS), area postrema and the dorsal motor nucleus of the vagus nerve. Recent identification of molecular and functional characteristics of the purinoceptors gave rise to an emerging view of the synaptic function of the extracellular purines such as ATP and its metabolite adenosine. Here I discuss three lines of evidence pointing to an essential role of ATP and adenosine receptors expressed on the synaptic terminal of the vagal primary afferents in the NTS: (1) target cell-dependent modulation of the frequency-filtering properties by adenosine of the primary afferent to second-order neuron transmission, (2) frequency-dependent involvement of P2X receptors in the pulmonary stretch receptor-mediated modulation of the central respiratory rhythm, and (3) suppression of adenosine-mediated presynaptic inhibition by in vivo gene silencing in the nodose ganglion. Supported by MEXT, Japan, 2005-2007. [J Physiol Sci. 2008;58 Suppl:S29]