Cellular localization of spinal A2A receptors giving rise to phrenic motor facilitation in rats

Cervical spinal adenosine 2A (A2A) receptor activation elicits plasticity in the phrenic motor system. For example, spinal A2A receptor-dependent phrenic motor facilitation (pMF) is observed following severe acute intermittent hypoxia (Nichols et al., 2012), and can be elicited by intrathecal A2A receptor agonist administration (Golder et al., 2008). Since the specific cells expressing the relevant A2A receptors for this form of phrenic motor plasticity are not known, we tested the hypothesis that the relevant A2A receptors are expressed in phrenic motor neurons per se. To test this hypothesis, we combined neurophysiology, neuropharmacology, immunofluorescence and RNA interference. Intrapleural injections of cholera toxin B subunit (CtB) were used to label phrenic motor neurons. Intrapleural injections of siRNAs (3 consecutive days) targeting A2A receptor mRNA (siA2A), or non-targeting siRNAs (siNT) were used to knock-down A2A expression within phrenic motor neurons. Successful knock-down of A2A receptors...