Fig. 6. Methylphenidate induces an increase in respiratory rate that is inhibited by droperidol. Time series of respiratory rate (red squares ) and tidal volume (blue circles ) recorded from one animal during inhalation of isoflurane (1.5%). Normal saline and intravenous (IV) methylphenidate (5 mg/kg) were administered at the indicated times. Methylphenidate induced a prompt and sustained increase in respiratory rate from 103 to 154 breaths/min (P < 10−16), whereas tidal volume remained essentially unchanged (A ). When a different animal was pretreated with IV droperidol (0.5 mg/kg) instead of normal saline, methylphenidate induced little change in respiratory rate or tidal volume (B ).
