Central nervous mechanisms in the generation of the pattern of breathing.
The role of the Bötzinger complex (BötC) and the pre-Bötzinger complex (pre-BötC) in the genesis of the breathing pattern was investigated in anesthetized, vagotomized, paralysed and artificially ventilated rabbits making use of bilateral microinjections of kainic acid (KA) and excitatory amino acid (EAA) receptor antagonists. KA microinjections into either the BötC or the pre-BötC transiently eliminated respiratory rhythmicity in the presence of tonic phrenic activity (tonic apnea). Rhythmic activity resumed as low-amplitude, high-frequency irregular oscillations, superimposed on tonic inspiratory activity and displayed a progressive, although incomplete recovery. Microinjections of kynurenic acid (KYN) and D(-)-2-amino-5-phosphonopentanoic acid (D-AP5) into the BötC caused a pattern of breathing characterized by low-amplitude, high-frequency irregular oscillations and subsequently tonic apnea. Responses to KYN and D-AP5 in the pre-BötC were similar, although less pronounced than those elicited by these drugs in the BötC and never characterized by tonic apnea. Microinjections of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) into the BötC and the pre-BötC induced much less intense responses mainly consisting of increases in respiratory frequency. The results show that the investigated medullary regions play a prominent role in the genesis of the normal pattern of breathing through the endogenous activation of EAA receptors.
Pantaleo
T
T
Dipartimento di Scienze Fisiologiche, Università di Firenze, Viale G.B. Morgagni 63, I-50134 Firenze, Italy. tito.pantaleo@unifi.it
Bongianni
F
F
Mutolo
D
D
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001683:Biological Clocks / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000502:physiology*; D009046:Motor Neurons / Q000502:physiology; D009415:Nerve Net / Q000187:drug effects / Q000502:physiology*; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology*; D010791:Phrenic Nerve / Q000502:physiology; D011817:Rabbits; D017470:Receptors, Glutamate / Q000187:drug effects / Q000502:physiology*; D012119:Respiration; D012125:Respiratory Center / Q000187:drug effects / Q000502:physiology*; D012143:Respiratory Physiological Phenomena; D013997:Time Factors
D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D017470:Receptors, Glutamate; D018698:Glutamic Acid