title: Electrical stimulation of the posteromedial thalamus modulates breathing in unanesthetized fetal sheep.
abstract: Having previously shown that lesions in the posteromedial group of thalamic nuclei abolish hypoxic inhibition of fetal breathing, we devised this study to identify thalamic loci that depress breathing by focal stimulation of specific sectors of the caudal thalamus and adjacent structures. Multipolar electrode arrays consisting of a series of eight stimulation contacts at 1.25-mm intervals were implanted vertically through guide cannulae into the caudal diencephalon of 12 chronically catheterized fetal sheep (>0.8 term), and central neural tissue was stimulated between adjacent contacts. Each site was stimulated repeatedly with increasing current searching for spatial and stimulus strength parameters for a reliable alteration in respiratory rate. Respiratory period increased when stimulation involved areas of the parafascicular nuclear complex (Pf), which more than doubled the mean period compared with the baseline of 0.90 +/- 0.19 s. The change in respiratory period was due to an increase in expiratory time, whereas inspiratory time and breath amplitude were not significantly affected. Breathing period and expiratory time were also increased when the stimulations involved the intralaminar wing surrounding the mediodorsal nucleus, the rostral central gray, zona incerta, and ventral tegmental area. Reductions in respiratory frequency occurred less consistently, with stimulation involving surrounding zones including the sub-Pf, ventromedial nucleus, and ventrobasal nuclear complex. These findings support the hypothesis that a restricted area of the posteromedial thalamus (principally Pf) constitutes part of a neuronal circuitry that modulates respiratory motoneurons.
authors.affiliation: Department of Obstetrics and Gynecology, and Neurobiology, Nicholas S Assali Perinatal Research Laboratory, Brain Research Institute, David Geffen School of Medicine at the University of California, Los Angeles, CA 90095-1740, USA. bkoos@mednet.ucla.edu
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Koos
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Kawasaki
authors.forename: Ashwinii
authors.initials: A
authors.lastname: Hari
authors.forename: Fanor
authors.initials: F
authors.lastname: Bohorquez
authors.forename: Calvin
authors.initials: C
authors.lastname: Jan
authors.forename: Jason
authors.initials: J
authors.lastname: Roostaeian
authors.forename: Charles L
authors.initials: CL
authors.lastname: Wilson
authors.forename: Lawrence
authors.initials: L
authors.lastname: Kruger
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D004565:Electroconvulsive Therapy; D005260:Female; D005333:Fetus / Q000502:physiology; D000860:Hypoxia / Q000503:physiopathology; D020646:Intralaminar Thalamic Nuclei / Q000196:embryology* / Q000502:physiology*; D009046:Motor Neurons / Q000502:physiology; D011247:Pregnancy; D015656:Respiratory Mechanics / Q000502:physiology*; D012756:Sheep; D017557:Ventral Tegmental Area / Q000502:physiology; D014851:Wakefulness