Fig. 1.
Episodic spinal serotonin type 2A (5-HT2A) or serotonin 7 (5-HT7) receptor activation elicits robust phrenic motor facilitation (pMF). A: representative traces of compressed integrated phrenic burst amplitude throughout the experimental protocol. Gray broken line in each trace represents baseline phrenic burst amplitude; arrows on top indicate time of it 5-HT2A receptor agonist (n = 4), 5-HT7 receptor agonist (n = 6), or artificial cerebrospinal fluid (ACSF) injections (n = 6). B: %change in phrenic burst amplitude (vs. baseline) at 30, 60, and 90 min after last it injection. C: delta (vs. baseline) in integrated phrenic burst amplitude at 90 min after last it injection. D: respiratory frequency at baseline and 30, 60, and 90 min after last it injection. E: end-tidal CO2 level at apneic and at recruitment threshold among experimental groups. Data are presented as means ± SD. Mixed 2-way ANOVA or 1-way ANOVA was used for overall group comparison (with Tukey’s adjustment when necessary), and differences were considered significant at P < 0.05. *5-HT2A receptor agonist different from baseline. #5-HT7 receptor agonist different from baseline.