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Role of C1‐C2 spinal neurons in vagal afferent modulation of upper thoracic spinal neurons with chemical and mechanical pulmonary inputs in rats
Author(s) -
Foreman Robert D,
Yang Xiaoli,
Farber Jay P,
Qin Chao
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a1271-b
Subject(s) - spinal cord , inhibitory postsynaptic potential , medicine , stimulation , noxious stimulus , excitatory postsynaptic potential , anesthesia , neuroscience , chemistry , receptor , nociception , biology
The aim of this study was to determine whether effects of vagal stimulation on thoracic spinal neurons with noxious pulmonary input depended on a relay in C1‐C2 spinal cord. Extracellular potentials of single upper thoracic (T3) spinal neurons were recorded in pentobarbital anesthetized, paralyzed, and ventilated male rats. Inhaled ammonia vapor (IA) and lung hyperinflation were used as independent noxious pulmonary stimuli. Left cervical vagal afferent stimulation (VAS) at 5, 10, 20, 30 V (0.2 ms, 50 Hz) was performed. A pledget with ibotenic acid (0.3 mg/ml, >15 min) was placed on the surface of C1‐C2 spinal cord to inactivate underlying neurons. VAS increased activity of 12 neurons excited by and 2 neurons inhibited by IA but decreased activity of 15 neurons excited by and 4 neurons inhibited by IA. For neurons excited by hyperinflation of lungs, VAS increased activity of 3/13 neurons but decreased activity of 7 neurons. Ibotenic acid on C1‐C2 abolished or reduced inhibitory effect of VAS on activity of 5/12 thoracic neurons. For 6 neurons that still responded to VAS after inactivation of C1‐C2 neurons, rostral C1 spinal transection eliminated all inhibitory (n=4) and excitatory responses (n=2) to VAS. These data suggested that C1‐C2 spinal neurons can serve in part as a relay for vagal afferent modulation of thoracic spinal processing for noxious chemical and mechanical pulmonary inputs. (NS‐035471, HL‐075524)