Effects of inactivation and stimulation of locus coeruleus on respiratory activity of neonatal rat.
We 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.
Hakuno
Haruhiko
H
Department of Medicine, School of Medicine, Keio University, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582, Japan.
Oyamada
Yoshitaka
Y
Murai
Michie
M
Ito
Yoko
Y
Yamaguchi
Kazuhiro
K
D000367:Age Factors; D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001933:Brain Stem / Q000166:cytology / Q000502:physiology; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology; D008125:Locus Coeruleus / Q000187:drug effects / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D009638:Norepinephrine / Q000502:physiology; D009924:Organ Culture Techniques; D010507:Periodicity; D051381:Rats; D017207:Rats, Sprague-Dawley; D012125:Respiratory Center / Q000166:cytology / Q000502:physiology*; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology
D000779:Anesthetics, Local; D013779:Tetrodotoxin; D009638:Norepinephrine