[The role of brain-stem vasomotor centers on the neurogenic control of cerebrovascular tonus. Part 2: The effect of stimulation of the medullary reticular formation on cerebrovascular tonus].
Acute brain swelling has been proposed to be caused by vasomotor paralysis secondary to disruption of metabolic and/or neurogenic control of cerebrovascular tone. In previous experiments, acute brain swelling was produced by stimulation of the reticular formation of the medulla oblongata (MORF) with destruction of the dorsomedial nucleus of the hypothalamus (DM) and the reticular formation of the midbrain (MBRF) in 2 (out of 56) animals. The purpose of the present study is to clarify the effect of stimulation of the MORF on cerebrovascular tone. Using 32 cats, blood pressure (BP), intracranial pressure (ICP) and cerebral blood volume (CBV) were continuously measured. The animals were divided into 4 groups: those in which the ICP was normal (Group A), those in which the ICP increased after subarachnoid hemorrhage (Group B), those which underwent superior cervical ganglionectomy (Group C) and those in which the spinal cord was transected at the C2 level (Group D). In all animals, the MORF was stimulated after the DM and MBRF were destroyed. Thirty minutes after cessation of stimulation, the BP was increased again by injection of angiotensin II until it reached the same level as with MORF stimulation. The vasomotor index (VI), defined by delta ICP/delta BP, was calculated and compared between the two situations. BP, ICP and CBV increased simultaneously immediately after MORF stimulation. In 29 out of the 32 animals, ICP increased abruptly from 2 to 48 mmHg and after ten seconds or more decreased gradually. The BP rose about 50 mmHg more slowly than the ICP. After cessation of MORF stimulation, BP, ICP and CBV returned to the control value.(ABSTRACT TRUNCATED AT 250 WORDS)
T
T
Nishiura
S
S
Nagao
T
T
Tanimoto
M
M
Kawauchi
M
M
Suga
T
T
Murota
F
F
Momma
Y
Y
Honma
I
I
Tsutsui
H
H
Kuyama
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure; D001808:Blood Vessels / Q000502:physiology*; D001921:Brain / Q000098:blood supply*; D001931:Brain Mapping; D002415:Cats; D003655:Decerebrate State / Q000503:physiopathology; D005728:Ganglia, Sympathetic / Q000502:physiology; D007427:Intracranial Pressure; D008526:Medulla Oblongata / Q000502:physiology*; D012154:Reticular Formation / Q000502:physiology*; D013345:Subarachnoid Hemorrhage / Q000503:physiopathology; D014666:Vasomotor System / Q000502:physiology*
D000804:Angiotensin II