Effects of chemical stimulation of the rostral ventrolateral medulla on cerebral and renal microcirculation in spontaneously hypertensive rats.
We investigated whether microcirculatory responses elicited by excitation of intrinsic neurons in the rostral ventrolateral medulla (RVLM) are altered in spontaneously hypertensive rats (SHR). SHR and Wistar-Kyoto rats (WKY) were anesthetized with chloralose, paralyzed with tubocurarine, and artificially ventilated. Cerebral and renal blood flows (CBF and RBF) were simultaneously measured using laser-Doppler flowmetry. Chemical stimulation of the RVLM neurons by microinjection of L-glutamate increased arterial pressure (AP) and heart rate in both SHR and WKY. Stimulation of the RVLM neurons also elicited stimulus-locked increase in CBF and decrease in RBF in both groups. The % changes in CBF and RBF were dose-dependent as stimulus intensity was increased and did not differ significantly between the SHR and WKY groups. Cerebral and renal vascular resistance (CVR and RVR) levels were calculated from changes in CBF or RBF and those in mean AP. The percent reduction in CVR and percent elevation in RVR were dose-dependent and did not differ significantly between the two groups. The data indicate that cerebral and systemic microcirculatory responses elicited by excitation of the RVLM neurons do not differ between SHR and WKY.
Chida
K
K
Department of Neurology, Nihon University School of Medicine, Tokyo, Japan. kchida@med.nihon-u.ac.jp
Miyagawa
M
M
Kawamura
H
H
Takasu
T
T
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D006973:Hypertension / Q000235:genetics / Q000503:physiopathology*; D008297:Male; D008526:Medulla Oblongata / Q000166:cytology / Q000187:drug effects*; D008833:Microcirculation; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D012079:Renal Circulation / Q000502:physiology*; D013268:Stimulation, Chemical