Neuroplasticity in nucleus tractus solitarius neurons after episodic ozone exposure in infant primates.
Acute ozone exposure evokes adverse respiratory responses, particularly in children. With repeated ozone exposures, however, despite the persistent lung inflammation and increased sensory nerve excitability, the central nervous system reflex responses, i.e., rapid shallow breathing and decreased lung function, adapt, suggesting changes in central nervous system signaling. We determined whether repeated ozone exposures altered the behavior of nucleus tractus solitarius (NTS) neurons where reflex respiratory motor outputs are first coordinated. Whole cell recordings were performed on NTS neurons in brain stem slices from infant monkeys exposed to filtered air or ozone (0.5 ppm, 8 h/day for 5 days every 14 days for 11 episodes). Although episodic ozone exposure depolarized the membrane potential, increased the membrane resistance, and increased neuronal spiking responses to depolarizing current injections (P < 0.05), it decreased the excitability to vagal sensory fiber activation (P < 0.05), suggesting a diminished responsiveness to sensory transmission, despite overall increases in excitability. Substance P, implicated in lung and NTS signaling, contributed to the increased responsiveness to current injections but not to the diminished sensory transmission. The finding that NTS neurons undergo plasticity with repeated ozone exposures may help to explain the adaptation of the respiratory motor responses.
Chen
Chao-Yin
CY
Department of Internal Medicine, School of Medicine, University of California at Davis, 95616, USA.
Bonham
Ann C
AC
Plopper
Charles G
CG
Joad
Jesse P
JP
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001713:Biphenyl Compounds / Q000494:pharmacology; D004334:Drug Administration Schedule; D004558:Electric Stimulation; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D008253:Macaca mulatta; D008564:Membrane Potentials / Q000187:drug effects; D009412:Nerve Fibers / Q000502:physiology; D064729:Neurokinin-1 Receptor Antagonists; D009473:Neuronal Plasticity; D009474:Neurons / Q000187:drug effects* / Q000502:physiology*; D009475:Neurons, Afferent / Q000502:physiology; D010083:Oxidants, Photochemical / Q000008:administration & dosage*; D010126:Ozone / Q000008:administration & dosage*; D010880:Piperidines / Q000494:pharmacology; D011812:Quinuclidines / Q000494:pharmacology; D017552:Solitary Nucleus / Q000187:drug effects* / Q000502:physiology*; D013569:Synapses / Q000502:physiology
D001713:Biphenyl Compounds; D064729:Neurokinin-1 Receptor Antagonists; D010083:Oxidants, Photochemical; D010880:Piperidines; D011812:Quinuclidines; C085215:SR 140333; D010126:Ozone; C066892:CP 96345