Possible modulation of the mouse respiratory rhythm generator by A1/C1 neurones

• Published in: Respiratory physiology & neurobiology Vol. 153; no. 2; pp. 126 - 138
• Main Authors: Zanella, Sebastien, Roux, J.C., Viemari, J.C., Hilaire, Gérard
• Format: Journal Article
• Language: English
• Published: Amsterdarm Elsevier B.V 28.09.2006; Elsevier
• Subjects: Adrenergic alpha-2 Receptor Antagonists; Adrenergic alpha-Antagonists; Adrenergic alpha-Antagonists - pharmacology; Age Factors; Analysis of Variance; Animals; Animals, Newborn; Biochemistry; Biochemistry, Molecular Biology; Biological and medical sciences; Catecholaminergic A1/C1 neurones; Catecholamines; Catecholamines - physiology; Cervical Vertebrae; Fundamental and applied biological sciences. Psychology; In Vitro Techniques; Life Sciences; Medulla Oblongata; Medulla Oblongata - cytology; Medulla Oblongata - physiology; Mice; Neural Pathways; Neural Pathways - cytology; Neural Pathways - physiology; Neurons; Neurons - cytology; Neurons - physiology; Periodicity; Receptors, Adrenergic, alpha-2; Receptors, Adrenergic, alpha-2 - physiology; Respiration; Respiratory Center; Respiratory Center - cytology; Respiratory Center - physiology; Respiratory rhythm; Spinal Cord; Spinal Cord - cytology; Spinal Cord - physiology; Vertebrates: respiratory system; Yohimbine; Yohimbine - pharmacology; α2 Adrenoceptors; Mice; α2 Adrenoceptors; Respiratory rhythm; Catecholaminergic A1/C1 neurones; α2-Adrenergic receptor; Vertebrata; Mammalia; Breathing rate; Mouse; Rodentia; Respiratory system
• ISSN: 1569-9048; 1878-1519
• DOI: 10.1016/j.resp.2005.09.009

Although compelling evidence exist that the respiratory rhythm generator is modulated by endogenous noradrenaline released from pontine A5 and A6 neurones, we examined whether medullary catecholaminergic neurones also participated in respiratory rhythm modulation. Experiments were performed in neonatal (postnatal days 0–6, P0-P6) and young mice (P14-P18) using “en bloc” medullary preparations (pons resected) and transverse medullary slices. In “en bloc” preparations, blockade of medullary α2 adrenoceptors with yohimbine and activation of catecholamine biosynthesis with l-tyrosine significantly depresses and facilitates the respiratory rhythm, respectively. In slices from neonatal and young mice, blockade of medullary α2 adrenoceptors also depressed the respiratory rhythm. Yohimbine local applications and lesion-ablation experiments of the dorsal medulla revealed implication of A1/C1 neurones in the yohimbine depressing effect. Although the mechanisms responsible for the yohimbine-depressing effect remain to be elucidated, our in vitro results in neonatal and young mice suggest that endogenous catecholamines released from A1/C1 neurones participate in respiratory rhythm modulation via medullary α2 adrenoceptors.