Abstract
It is still a matter of dispute whether the cervical sympathetic nervous system plays an important role in cerebral blood flow (CBF) autoregulation. The purpose of the present study is to investigate quantitatively whether the cervival sympathetic pre- or postganglionic nerve participates more effectively in CBF autoregulation.
Thirty-nine monkeys were anesthetized with α-chloralose and urethane, kept at 37.5±0.5°C of body temperature and 34.6±3.7 mmHg of PaCO2. Cervical sympathetic nerves and internal carotid arteries were isolated using microsurgical technique. Internal carotid blood flow (ICBF) was measured by an electromagnetic flowmeter and changes in mean arterial blood pressure (ΔMABP) were induced by exsanguination and reinfusion of the blood. CBF autoregulation was analyzed by dysautoregulation index (D.I.=ΔICBF/ΔMABP, ml/min/mmHg).
Results : 1) Following the preganglionectomy, the D.I. showed a tendency to increase from 0.10±0.16 ml/min/mmHg to 0.20±0.15 during induced mild hypotension (ΔMABP<20 mmHg). 2) After the postganglionectomy, the D.I. increased significantly from 0.05±0.04 ml/min/mmHg to 0.12±0.10 (p<0.02) during induced moderate hypotension (ΔMABP≥20 mmHg). 3) No significant changes in D.I. were observed in cases of mild or moderate alteration in blood pressure during reinfusion of the blood.
The above data suggest that the cervical sympathetic postganglionic nerve regulates more specificially the tone of the cerebrovascular vessels during induced hypotension.
