Do vasomotor nerves significantly regulate cerebral blood flow?

Summary:To investigate the role of sympathetic regula tion in both resistance and capacitance vessels in cerebral circulation, the responses of pial and intraparenchymal vessels to sympathetic nerve stimulation were simulta neously examined in 14 cats by means of a newly devel oped video camera photoelectric system. The system consisted of a video camera system for measurement of pial vascular diameters and a photoelectric apparatus for estimating regional cerebral blood volume in the intrapa renchymal vessels. The ipsilateral superior cervical gan glion was electrically stimulated for 5 min. Initially. both the pial and intraparenchymal vessels constricted. TheIt is well documented that sympathetic nerves derived from the superior cervical ganglion con strict cerebral vessels down to the pial arterioles and venules (Auer et aI. , 1982) and exert a protec tive effect against breakthrough of autoregulation of CBF during acute hypertension (Bill and Linder, 1976). However, the role of the sympathetic nerves in the regulation of the resting CBF is still disputed Purves, 1978). This controversy seems to depend partly on the method ological limitations of measuring CBF and on the homeostatic mechanism of cerebral circulation. Harper et al. (1972) hypothesized that under most circumstances, sympathetic constriction of the ex traparenchymal and pial vessels might be com pen- 342large pial arteries (173 ± 25 f.Lm, mean ± SEM) remained constricted throughout the stimulation. whereas the in traparenchymal vessels began to dilate after the initial constriction and exceeded the control level at 175 ± 25 s despite continued stimulation. In conclusion. such sym pathetic nerve stimulation is considered to exert a con strictive effect on the intraparenchymal as well as the pial vessels at the early stage. The compensatory dilation of the intraparenchymal vessels was delayed 3 min after ini tiation of the stimulation. Key Words: Cerebral blood volume-Escape phenomenon-Pial vessel-Sympa thetic stimulation. sated for by a metabolic dilation of the intraparen chymal vessels and that CBF might be kept con stant. Recently, we developed a video camera photoelectric system that permits simultaneous and continuous measurement of pial vascular diameter and changes in regional cerebral blood volume (CBV). In the present study, to test Harper et al. 's hypothesis, we compared the responses of pial and intraparenchymal vessels to superior cervical gan glion stimulation by using this new method. MATERIALS AND METHODSExperiments were performed on 14 cats weighing from 2.3 to 3.4 kg, anesthetized by intraperitoneal injection of a-chloralose (50 mg/kg) and urethane (5 00 mg/kg). The bilateral femoral arteries and one femoral vein were can nulated for monitoring arterial blood pressure (BP). ana lyzing blood gases. and injection of drugs. The animals were subjected to tracheostomy and were ventilated with a respirator (Harvard 662) after immobilization with al curonium chloride (2 mg i.v.). The animal's head was fixed in a stereotactic head ho...

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Comparison between Pial and Intraparenchymal Vascular Responses to Cervical Sympathetic Stimulation in Cats. Part 1. Under Normal Resting Conditions

Gotoh

Fukuuchi

Amano

et al. 1986

“…The existence of nerve supplies to the pial, dural, and intracerebral blood vessels is well known, but their role in the regulation of cerebral blood flow (CBF) has been a matter of speculation and debate over much of this century (Wolff, 1936;Lassen, 1959;Sokoloff, 1959;Owman and Edvinsson, 1977;Heistad and Marcus, 1978;Kuschinsky and Wahl, 1978;Purves, 1978;Owman and Hardebo, 1986;Lou et aI., 1987;Edvinsson et aI., 1993). The most widely accepted view has been that CBF is regu-( + 31 %), and frontal cortices (+ 56%) and the caudate putamen ( + 27%) above control values (n = 9).…”

mentioning

confidence: 99%

Role of the Cerebellar Fastigial Nucleus in the Physiological Regulation of Cerebral Blood Flow

Takahashi

Crane

Jehle

et al. 1995

Summary: Local cerebral blood flow (lCBF) was mea sured with P4Cliodoantipyrine in conscious, unrestrained rats during electrical stimulation of the fastigial nucleus (FN). Electrode position in the FN was determined by blood pressure (MABP) responses to stimulation under anesthesia. In nine rats in which MABP responses had been variable under anesthesia, bipolar stimulation (50 Hz, 0.5 ms, I s on/ I s om with currents of 30-100 /-LA after recovery from anesthesia produced stereotypic behavior but little effect on MABP and ICBF. In seven other con scious rats currents could be raised to 75-200 /-LA without inducing seizures, resulting in sustained MABP eleva tions during the ICBF measurement and significantly in creased ICBF in the sensory-motor (+ 45%), parietalThe existence of nerve supplies to the pial, dural, and intracerebral blood vessels is well known, but their role in the regulation of cerebral blood flow (CBF) has been a matter of speculation and debate over much of this century (

“…on various aspects of cerebrovascular responses (Purves, 1972) and several improvements of the classical technique have been made (Forbes, 1928;Gurdjian et aI., 1958;Wahl et aI., 1973;Harper and MacKenzie, 1977;Auer and Haydn, 1979;Okayasu et aI., 1979). This method, however, has yielded only indirect information about the level of the blood flow (Purves, 1972).…”

mentioning

confidence: 99%

Video Camera Method for Simultaneous Measurement of Blood Flow Velocity and Pial Vessel Diameter

Gotoh

Muramatsu

Fukuuchi

et al. 1982

Summary:A new method for the simultaneous measurement of blood flow velocity and pial vessel diameter is described. The system consists basically of a high-sensitivity vidicon camera, camera control, width analyzer, video den sitometer, TV monitor, desktop computer, and multi-pen recorder. The pial vessels are visualized through a cranial window at 25 -200 x magnification on the TV monitor. The diameter of three target vessels can be recorded simulta neously on the recorder by adjustment of controllable video signal gates using the width analyzer. At the same time, the optical densities of two targets at points upstream and downstream of the pial vessel are measured continuously with video densitometers, and their outputs are recorded on the polygraph and analyzed by the computer. The time difference in the two peaks of time-con centration curves, produced every 2-3 s at the highest frequency by the injec tion of a small amount of saline through the lingual artery, is measured on-line using the computer. The flow velocity in the vessel is calculated from the time difference and the distance between the two targets. The system was shown to be stable, reliable, and rapid in response. This method may provide a useful tool for research in the field of blood circulation in the brain or any other organ.