Influence of different classes of anesthetics on the acute hypoxic ventilatory response (HVR) in adult Sprague‐Dawley rat in vivo

Previous work from our laboratory indicates that anesthetics other than urethane (U), which is commonly used in central respiratory control studies, may serve as appropriate alternatives for studying eupnea and/or gasping in vivo. This work, however, did not investigate the effects of any of the anesthetics studied on the acute HVR. Therefore, the current study examined the effects of the long‐lasting sedative‐hypnotic U (n=10), the long‐lasting barbiturate inactin, which was evaluated alone (IN, n=6) or in combination with the dissociative ketamine (IN‐K, n=8) or the analgesic thiazole xylazine (IN‐X, n=3), the short‐acting barbiturate sodium pentobarbital (P, n=9), ketamine in combination with xylazine (K‐X, n=4), the inhalant anesthetic isoflurane (ISO, n=15), and the non‐barbiturate sedative propofol (PRO, n=4) on the acute HVR. We found that for most of the anesthetics examined, frequency (freq) and amplitude (amp) increased by 20–60% and ≥75%, respectively, although freq increased by 140% for K‐X and amp increased by ≥115% for IN‐X and K‐X. The onset to freq and amp effects was seen within ≤12 bursts for U, IN, IN‐K, IN‐X, and K‐X, but was delayed until ≥25 bursts for PRO and ISO; for P, amp effects were within ≤10 bursts but freq effects were delayed. The HVR duration was varied. These data support the need for further studies examining different anesthetics on central respiratory control. Supported by HL63175