Figure 2.

IH-1 significantly reduced AIH-induced pLTF. A–C, Representative integrated phrenic neurograms during AIH protocols for rats receiving normoxia (A), IH-1 (B), and time control (no AIH, C). Development of pLTF is evident as a progressive increase in phrenic nerve amplitude from baseline (black dashed line) over 60 min in normoxic rats, but not in IH-1-treated or time control rats. D, Previous exposure to IH-1 did not alter the short-term hypoxic ventilatory responses (76 ± 11%) versus normoxia-treated (76 ± 8%) rats (t test). E, pLTF was abolished after IH-1 (−1 ± 5%, n = 6) compared to normoxia-treated (56 ± 10%, n = 6) rats. No increase in phrenic nerve amplitude was evident in time control rats (8 ± 10%, n = 6). ***p < 0.001 (significant difference from normoxia, two-way RM ANOVA, Fisher LSD post-test).