Effects of chemical stimulation of the caudal ventrolateral medulla on cerebral and renal microcirculation in rats

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Journal of the

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Autonomic Nervous System ELSEVIER

Journal of the Autonomic Nervous System 50 (1995) 359-384

ABSTRACTS: The Autonomic Nervous System Effects of Chemical Stimulation of the Caudal Ventrolateral Medulla on Cerebral and Renal Microcirculation in Rats Wataru Usui, Koichi Chida *, Mizuo Miyagawa, Hiroshi Kawamura, Toshiaki Takasu * and Tadao Yasugi

Second Department of Internal Medicine, * Department of Neurology, Nihon University School of Medicine, Tokyo 1 73, Japan We investigated the role of neurons in the caudal ventrolateral medulla (CVL) on cerebral and renal microcirculation in rats. The animals were anesthetized with chloralose, paralyzed with tubocurarine, and artificially ventilated. Cerebral and renal blood flow were measured simultaneously by means of laser-Doppler flowmetry. Chemical stimulation of the CVL neurons by microinjection of the excitatory amino-acid Lglutamate decreased arterial pressure and heart rate. The stimulation induced also a stimuluslocked decrease in cerebral blood flow and an increase in renal blood flow. The percentage change in cerebral blood flow was dose-dependent as the stimulus intensity was increased. From the changes in cerebral and renal blood flow and in arterial pressure we calculated the cerebral and the renal vascular resistance. The increase in cerebral vascular resistance and the decrease in renal vascular resistance were dose-dependent. Blood withdrawal reduced arterial pressure by a similar degree as the medullar stimulation, but did not significantly decrease cerebral blood flow. We have previously shown that neurons in the rostral ventrolateral medulla influence cerebral and renal microcirculation in rats. The present results suggest that neurons of the caudal ventrolateral medulla in conjunction with neurons of

the rostral ventrolateral medulla, integrate cerebral and systemic circulation. (The Autonomic Nervous System, 30 (1993) 351-357) Compensation for Lower Limb Blood Pooling Related to One-Minute Wave in Body Fluid Volume and Muscle Sympathetic Nerve Activity during Active-Static Standing in Man Kinsaku Inamura *'**, Tadaaki Mano * and Satoshi lwase*

• Department of Autonomic and Behavioral Neurosciences, Division of Higher Nervous Control, Research Institue of Environmental Medicine, Nagoya University, Nagoya 464-01, ** Department of Physical Education, Faculty of Liberal Arts, Shizuoka University, Shizuoka 422, Japan We investigated the sympathetic control mechanism involved in the 1-min waves in body fluid volume. To this effect, the 1-min waves (0.0120.022 Hz) in muscle sympathetic nerve activity was recorded by microneurography in human subjects during active-static standing and was analyzed by spectral analysis. In the same subjects the l-rain waves in body fluid volume was analyzed by rubber strain gauge plethysmography. One-rain waves were also measured for other hemodynamic parameters in order to estimate the phase differences. The subjects were four healthy male volunteers aged 21-32 years. The phase order referred to the l-rain waves in the electromyographic data from the soleus was as follows: (1) the intrathoracic fluid volume was decreased; (2) the venous pressure at the dorsum pedis was increased; (3) muscle sympathetic nerve activity was enhanced; (4) the calf fluid volume

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