Activation of intra-nodose ganglion P2X7 receptors elicit increases in neuronal activity

The vagus nerve innervates several organs including the heart, stomach and pancreas among others. Somas of sensory neurons that project through the vagal nerve are located into the nodose ganglion. The presence of purinergic receptors has been reported in neurons and satellite glial cells in several sensory ganglia. In the nodose ganglion, calcium depletion-induced increases in neuron activity can be partly reversed by P2X₇ blockers applied directly into the ganglion. The later suggest a possible role of P2X₇ receptors in the modulation of neuronal activity within this sensory ganglion. We aimed to characterize the neuronal response to the P2X₇ activation in neurons located in the nodose ganglion under physiological conditions. Using an ex-vivo preparation for electrophysiological recordings of the neural discharges of nodose ganglion neurons, we found that applications of both ATP and Bz-ATP (a selective P2X 7 receptor agonist) induce a transient increase of the neuronal activity. Also, we found a concentration dependent increase in neural activity in response to Bz-ATP (ED₅₀ = 0.55 mM) with a clear desensitization when applied every ~30 sec. Isolated nodose ganglion neuron electrophysiological recordings reveal no differences in the response to Bz-ATP and ATP. Finally, we showed that the P2X₇ receptor was constitutively express in the nodose ganglion in both neurons and satellite glial cells. Our results showed the presence of functional P2X 7 receptors under physiological conditions within the nodose ganglion of the rat and suggest that ATP modulation of nodose ganglion activity may be in part mediated by activation of P2X 7 receptors.