Sympathetic innervation of pulmonary circulation and its role in hypoxic pulmonary vasoconstriction

The purposes of this study were to localize the position of spinal center of sympathetic nerve which controls the pulmonary circulation, and to evaluate the role of pulmonary sympathetic nerve in hypoxic pulmonary vasoconstriction (HPV) in pithed rat model. The sympathetic preganglionic fibers arising from C₇–T₁₀ segments were stimulated electrically in succession. During stimulation the pulmonary vascular resistance (PVR) was increased in all segments tested, most significantly in C₇-T₄ (about 28 % above control value), obviously higher than that in T₅-T₁₀. The higher the stimulated spinal segments, the larger the ratio of ΔPVR/ΔSVR. Alveolar hypoxia (12%O₂–88% N₂) could induce HPV in pithed rat. In the presence of hypoxia, stimulation of T₁–T₃ segments caused a double increment in PVR and -P_p, as compared with those during normoxia (P<0.05). The data show that 1) the spinal center of sympathetic nerve regulating the vasomotion of pulmonary circulation is located in the C₇-T₄ segments; 2) the excitation of sympathetic nervous system during hypoxia could enhance HPV.