Stimulation of C1 Area Neurons Globally Increases Regional Cerebral Blood Flow but Not Metabolism

Abstract

Summary:We examined the effects of electrical and chemical stimulation of the C1 area of the rostral ventro lateral medulla (RVL) on regional cerebral blood flow (rCBF) and regional cerebral glucose utilization (rCGU) in anesthetized (chloralose), paralyzed (curare) and ven tilated rats. rCBF and rCGU were measured using 14C_ iodoantipyrine (lAP) and 14C-deoxyglucose (2-DG), re spectively, as indicators, with bilateral regional dissec tion of 11 brain regions. Electrical stimulation of the RVL elicited increases in arterial pressure (AP), heart rate (RR) 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-The rostral ventrolateral medulla (RVL) plays a critical role in the control of the systemic circula tion. Sympathoexcitatory reticulospinal neurons of the RVL not only appear necessary for maintaining resting (tonic) levels of arterial pressure (AP), but are also critical in mediating a number of reflexes

Nitric Oxide and Prostanoids Participate in Cerebral Vasodilation Elicited by Electrical Stimulation of the Rostral Ventrolateral Medulla

“…Elevations of rCBF elicited from the R VL were graded with respect to stimulus frequency and in tensity, with optimal parameters comparable to those reported by Underwood et al (1992). The op timal stimulus frequency was 50 Hz, and the thresh old current between 10 and 20 j.LA, with the re sponse increasing linearly as the current was in creased to reach a maximum (at 50 Hz) near 50 j.LA.…”

“…The op timal stimulus frequency was 50 Hz, and the thresh old current between 10 and 20 j.LA, with the re sponse increasing linearly as the current was in creased to reach a maximum (at 50 Hz) near 50 j.LA. Microinjection into this site of L-glutamate (L-Glu) (5 nM in 20 nl) or kainic acid (KA) (5 nM in 20 n1) increased rCBF by 14.8 ± 8.4% (p < 0.05; n = 5) and 94.5 ± 14.1% (p < 0.001; n = 3), respectively, indicating that the effect on rCBF is attributable to excitation of local neurons (Underwood et al, 1992). Electrical stimulation of the RVL in spinal- ized rats elicited a short-latency elevation of rCBF and decreased CVR by 16 ± 4% (p < 0.05).…”

Neurons of a Limited Subthalamic Area Mediate Elevations in Cortical Cerebral Blood Flow Evoked by Hypoxia and Excitation of Neurons of the Rostral Ventrolateral Medulla

“…Lesion of the MCVA reverses cerebrovasodilation evoked by RVLM excitation or by hypoxia (Underwood et al, 1992;. Electrical or chemical stimulation of the MCVA increases rCBF independently of metabolism in parallel with the decrease of CVR (Underwood et al, 1992; and the increase in power of a 4 -6 Hz component of cortical EEG (Golanov et al, 2000b). To explore the ascending pathway relaying the vasodilator signal from the MCVA to the telencephalon, we systematically surveyed the thalamic region with electrical stimulation, searching for sites that are capable of increasing rCBF globally.…”

“…However, because the effects on rCBF and EEG elicited by hypoxic or electrical stimulation of RVLM are bilateral and diffuse (Underwood et al, 1992;, it is likely that distal neurons in the chain arise from nuclei that diffusely project to the cortex. These would include areas such as the midline thalamic/centromedian complex (for review, see Jones, 1985;Price, 1995) and the basal forebrain (BF) (Saper and Loewy, 1980;Wenk et al, 1980;Eckenstein et al, 1988).…”

“…In addition, there is a widespread increase in regional cerebral blood flow (rCBF) without change in a cerebral metabolism [as evaluated by regional cerebral glucose utilization (rCGU)] and synchronization of the EEG (Underwood et al, 1992(Underwood et al, , 1994Golanov and Reis, 1996;Golanov et al, 2000b;). The integrated response simulates the oxygenconserving (diving) reflex of mammals, an integrated pattern of responses considered to protect the brain from hypoxia by redirecting blood from the systemic to cerebral circulation in response to submersion or other stimuli activating the network (Butler, 1982;Blix and Folkow, 1983).…”