Caudal ventrolateral medullary depressor area controls cerebral circulation via rostral ventrolateral medullary pressor area.
The cerebral blood flow (CBF) was determined by radiolabeled microsphere technique in urethane (1.1-1.5 g.kg-1, i.p.) anesthetized Wistar rats. Microinjection of L-glutamate (1.7 nmol) into the ventrolateral medullary depressor area (VLDA) produced a significant (P < 0.01) decrease in CBF from 64 +/- 9 (mean +/- S.E.M.) to 48 +/- 9 ml.min-1.(100g)-1 and a significant (P < 0.01) increase in cerebrovascular resistance (CVR) from 1.7 +/- 0.2 to 2.4 +/- 0.4 mmHg per [ml.min-1.(100g)-1] in the cerebral cortex ipsilateral to the stimulated VLDA side but not in other structures such as brain stem and cerebellum (n = 9). Cervical sympathectomy blocked the decrease in CBF and increase in CVR elicited by chemical stimulation of the VLDA (n = 10). Depression of the ventrolateral medullary pressor area (VLPA) neurons induced by microinjection of muscimol into the VLPA blocked the CBF decrease and CVR increase following chemical stimulation of the VLDA (n = 11). Microinjection of the vehicle solution into the VLDA had no effects on systemic and cerebral circulation (n = 7). These results suggest that a vasoconstrictor pathway to control cerebral vessels involves an excitatory projection from the VLDA to the VLPA and the changes in cerebral circulation are mediated by the cervical sympathetic nerves.
Department of Systems Physiology, University of Occupational and Environmental Health, Kitakyushu, Japan.
M
M
Maeda
M
M
Inoue
S
S
Takao
Y
Y
Hayashida
M
M
Nakai
A J
AJ
Krieger
H N
HN
Sapru
D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D018698:Glutamic Acid / Q000008:administration & dosage / Q000494:pharmacology; D006339:Heart Rate / Q000502:physiology; D008297:Male; D008526:Medulla Oblongata / Q000033:anatomy & histology / Q000502:physiology*; D008845:Microinjections; D009118:Muscimol / Q000008:administration & dosage / Q000494:pharmacology; D009434:Neural Pathways / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D013562:Sympathectomy; D014655:Vascular Resistance / Q000187:drug effects; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology
D009118:Muscimol; D018698:Glutamic Acid