• Haruhiko Hakuno, Yoshitaka Oyamada, Michie Murai, Yoko Ito, and Kazuhiro Yamaguchi.
• Department of Medicine, School of Medicine, Keio University, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582, Japan.
• Respir Physiol Neurobiol. 2004 Apr 20; 140 (1): 9-18.

AbstractWe examined the effects of pharmacological inactivation and electrical stimulation of the locus coeruleus (LC) on the respiratory rate (RR) in isolated brainstem-spinal cord preparations of the neonatal rat. The brainstem and spinal cord were isolated en bloc from neonatal (days 1-4) Sprague-Dawley rats and superfused with artificial cerebrospinal fluid (ACSF) equilibrated with a gas mixture containing 2% CO(2) (pH 7.8). Pharmacological inactivation of the bilateral LC by means of microinjection of tetrodotoxin or noradrenaline elicited a significant decrease in RR in preparations obtained from rats aged 3-4 days, but not in preparations of rats aged 1-2 days. Stimulation of the bilateral LC with a train of electrical pulses (25-50 microA, 30 ms, 0.5 Hz, 3-4 min) caused a marginal but significant increase in RR on days 3-4, but not on days 1-2. These results indicate that the LC exerts an excitatory effect on the medullary respiratory rhythm generator in an age-dependent manner.

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