Fig. 2

Systemic LPS prevents phrenic long-term facilitation (LTF) via activity of cervical spinal okadaic acid-sensitive serine/threonine protein phosphatases. a Representative integrated inspiratory phrenic (Phr) and hypoglossal (Xii) neurograms before, during and for 90 min after moderate acute intermittent hypoxia (mAIH) in a sham-vehicle (i and ii) and a LPS-treated rat (iii and iv) receiving cervical spinal okadaic acid. While cervical spinal okadaic acid administration did not interfere with the development of LTF in the sham-vehicle treated rat (i and ii) the same intervention restored phrenic LTF in rats that had received LPS (iv). b Mean group data demonstrating that by 90 min post hypoxia, inspiratory phrenic and hypoglossal nerve amplitude was significantly enhanced above baseline levels (baseline = 0) in sham vehicle treated rats receiving cervical spinal okadaic acid. In rats pre-treated with systemic LPS, cervical spinal okadaic acid restored phrenic LTF, whereas as expected, hypoglossal nerve amplitude remained near baseline levels throughout the 90-minute recording period. Values are normalized means ± SE. *Significant difference compared to baseline; ^#significant difference compared to respective LPS-treated group at the indicated time point: for all, p < 0.05. Hx1, Hx2, Hx3, hypoxic episodes 1, 2, and 3; Phr, phrenic; xii, hypoglossal; pLTF, phrenic long-term facilitation; xiiLTF, hypoglossal long-term facilitation; O.A., okadaic acid