• Masanori Kashiwagi, Yoshimune Osaka, Hiroshi Onimaru, and Junzo Takeda.
• Department of Anaesthesiology, Kitasato Institute Hospital, Kitasato UniversityDepartment of Physiology, Showa University School of MedicineDepartment of Anaesthesiology, School of Medicine, Keio University, Tokyo, Japan.
• Clin. Exp. Pharmacol. Physiol. 2011 Mar 1;38(3):186-91.

Abstract1. Propofol (2,6-diisopropylphenol) is an intravenous anaesthetic used for the induction and maintenance of general anaesthesia; it also potently and dose-dependently depresses respiration. The aim of the present study was to analyse propofol-induced changes in spatiotemporal patterns of inspiratory-related neural activity and to investigate the involvement of the GABAA receptor by using an optical imaging technique. 2. The brain stems and spinal cords of 0-1-day-old Wistar rats were isolated and stained using a fluorescent voltage-sensitive dye. Neuronal activity in the preparation was detected using an optical recording apparatus containing a charge-coupled device (CCD)-based camera. 3. Bath-applied propofol (7.5 μmol/L) decreased the C4 burst rate to 45.9% of baseline. Although optical signals corresponding to membrane depolarization during the pre-inspiratory phase in the parafacial region of the ventral medulla decreased to 28.7% of baseline following propofol application, those during the inspiratory phase in the caudal part of the rostral ventrolateral medulla did not. 4. The inhibitory effect of bath-applied propofol was reversed by 2 μmol/L bicuculline. 5. Changes in optical signals corresponding to the population activity of pre-inspiratory neurons were parallel to changes in the C4 burst rate. 6. The results suggest that propofol decreases the inspiratory burst rate by reducing the activity of pre-inspiratory neurons and that GABAA receptor activation plays a role in propofol-induced central respiratory depression. These results are consistent with those of previous electrophysiological studies.© 2011 The Authors. Clinical and Experimental Pharmacology and Physiology © 2011 Blackwell Publishing Asia Pty Ltd.

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