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cAMP‐dependent modulation of I h underlies the P2Y 1 receptor‐mediated excitation of the preBötzinger Complex inspiratory network in vitro
Author(s) -
Zhang Yong,
Biancardi Vivian,
Tapia Ana Miranda,
Jaib Toka Abu,
Gourine Alexander,
Kasparov Sergey,
Funk Gregory Douglas
Publication year - 2019
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2019.33.1_supplement.551.8
Subject(s) - depolarization , long term potentiation , hyperpolarization (physics) , biophysics , chemistry , agonist , electrophysiology , receptor , medicine , endocrinology , biology , nuclear magnetic resonance spectroscopy , organic chemistry
The ventilatory response to hypoxia comprises an initial peripheral chemoreceptor‐mediated increase in ventilation followed by a centrally‐mediated secondary depression that can be life‐threatening in premature infants with apnea. ATP appears to be released from astrocytes in the preBötzinger Complex (preBötC, critical site for inspiratory rhythm generation), during hypoxia where it attenuates the secondary depression via a P2Y 1 receptor (R)‐dependent excitation of inspiratory neurons. Here we apply nerve and whole‐cell recording methods to rhythmic medullary slices (700 μM) from neonatal rat to test the hypothesis that the P2Y 1 R‐mediated excitation of the preBötC network is mediated via cAMP‐dependent modulation of the hyperpolarization‐activated inward current, I h , in inspiratory neurons. Local application of MRS2365 (P2Y 1 R agonist, 100 μM) evoked, in a subpopulation of inspiratory neurons (~33%), inward currents that reversed between −40 and −60 mV, consistent with activation of I h . MRS2365 also potentiated the sag current, characteristic of I h , that was progressively activated with hyperpolarizing voltage pulses from −50 to −110 mV (10 mV increments; 32 ± 6% potentiation measured at −100 mV). Comparison of I h activation curves, produced via analysis of tail currents evoked by a series of 10 mV hyperpolarizing steps from −50 mV to −140 mV, in control and MRS2365, revealed a 6.6 mV, MRS2365‐induced depolarizing shift in V 1/2 (V m at which 50% of HCN channels are open). The MRS2365 inward current and its potentiation of I h were blocked by local pre‐application of ZD 7288 (open channel blocker of I h , 100 μM). At the network level, pre‐application of ZD 7288 at 100 μM and 25 μM attenuated the MRS2365‐induced frequency increase in inspiratory‐related activity by 94 ± 3% and 70 ± 12%, respectively. 15‐min intracellular dialysis of SQ 22536 (adenylyl cyclase inhibitor, 100 μM) from the whole‐cell pipette significantly attenuated the MRS2365 currents by 60 ± 4%. Similarly, SQ 22536 (1 mM and 100 μM for local and bath application respectively) attenuated the MRS2365‐induced frequency increase by 67 ± 8%. These data suggest that the P2Y 1 R‐mediated excitation of the preBötC network is produced, at least in part, via a cAMP‐dependent modulation of I h in a subpopulation of inspiratory neurons. Support or Funding Information CIHR, AIHS, NSERC, CFI, and WCHRI This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .