Changes in phrenic (A) and XII (B) burst amplitudes (percent change from baseline) in rats receiving 5-HT7 antagonist + AIH (SB269970, ■, n = 8), vehicle + AIH (saline, ◆, n = 8) and control rats not receiving AIH (i.e., time controls) SB269970 (□, n=5) and vehicle (◇, n=7). Compared to vehicle, intrathecal SB269970 enhanced phrenic burst amplitude responses following AIH. However, similar enhancement of XII LTF (B) was not observed, suggesting that drug distribution was restricted to the spinal cord. Values are means±S.E.M. *different than vehicle + AIH, #different than vehicle control, †different than 5-HT7 antagonist control, RMANOVA, p<0.05.