Stimulation of C1 area neurons globally increases regional cerebral blood flow but not metabolism

Abstract

We examined the effects of electrical and chemical stimulation of the C1 area of the rostral ventrolateral medulla (RVL) on regional cerebral blood flow (rCBF) and regional cerebral glucose utilization (rCGU) in anesthetized (chloralose), paralyzed (curare) and ventilated rats. rCBF and rCGU were measured using 14Ciodoantipyrine (IAP) and 14C-deoxyglucose (2-DG), respectively, as indicators, with bilateral regional dissection of 11 brain regions. Electrical stimulation of the RVL elicited increases in arterial pressure (AP), heart rate (HR) and plasma concentration of epinephrine (EPI) and norepinephrine (NE). In addition, stimulation of the RVL, but not the adjacent medial longitudinal fasciculus, with AP maintained, increased rCBF (p < 0.05, n = 6), but not rCGU, bilaterally and symmetrically (134-169% of control) throughout the brain. Bilateral adrenalectomy abolished the increase in plasma EPI elicited by stimula-tion of the RVL but did not affect resting rCBF (n = 5) or the elevation in rCBF elicited by RVL stimulation (n = 5). Increases in rCBF elicited by RVL stimulation were also unaffected by acute transection of the superior cervical ganglion (p > 0.05). Kainic acid (KA) microinjected into the RVL unilaterally (n = 6) at a dose producing sustained elevation in AP (5 nmol in 100 nl), elicited changes in rCBF similar to those elicited by electrical stimulation. We conclude that neurons within the RVL, possibly those of the adrenergic C1 group, can initiate a global cerebrovasodilation, but not an increase in rCGU, largely through neural pathways intrinsic to the brain. The responses may represent activation of networks in RVL mediating circulatory adjustments to hypoxia.