The severity of asthma is closely related to the intensity of airway vagal activity; however, it is unclear how airway vagal activity is centrally augmented in asthma. Here we report that in an asthma model of male Sprague-Dawley rats, the expression and activity of ecto-5'-nucleotidase (CD73) were decreased in airway vagal centers, ATP concentration in cerebral spinal fluid was increased, and the inhibitory and excitatory airway vagal responses to intracisternally injected ATP (5 μmol) and CD73 inhibitor AMPCP (5 μmol), respectively, were attenuated. In airway vagal preganglionic neurons (AVPNs) identified in medullary slices of neonatal Sprague-Dawley rats, AMPCP (100 μmol·L-1) caused excitatory effects, as are shown in patch-clamp by depolarization, increased neuronal discharge, and facilitated spontaneous excitatory postsynaptic currents (sEPSCs). In contrast, exogenous ATP (100 μmol·L-1, 1 mmol·L-1) primarily caused inhibitory effects, which are similar to those induced by exogenous adenosine (100 μmol·L-1). Adenosine A1 receptor antagonist CPT (5 μmol·L-1) blocked the inhibition of sEPSCs induced by 100 μmol·L-1 exogenous ATP and that by 100 μmol·L-1 exogenous adenosine, whereas 50 μmol·L-1 CPT converted the inhibition of sEPSCs induced by 1 mmol·L-1 ATP to facilitation that was blocked by addition of P2X receptor antagonist PPADS (20 μmol·L-1). These results demonstrate that in rat, the sEPSCs of AVPNs are facilitated by extracellular ATP via activation of P2X receptors and inhibited by extracellular adenosine via activation of A1 receptors; in experimental asthma, decreased CD73 expression and activity in airway vagal centers contribute to the augmentation of airway vagal activity through imbalanced ATP/ADO modulation of AVPNs.
Keywords: airway; asthma; ecto-5′-nucleotidase; neuron; patch-clamp; vagus nerve.