Caudal ventrolateral medullary depressor area controls cerebral circulation via rostral ventrolateral medullary pressor area

Abstract

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.

Cerebral blood flow decreases following microinjection of sodium nitroprusside into the nucleus tractus solitarii of anesthetized rats

“…It is known that the following pathways mediate the control of ABP: an excitatory projection from the NTS to the caudal ventrolateral depressor area (VLDA) in the medulla and an inhibitory GABAergic projection from the VLDA to the rostral ventrolateral pressor area (VLPA), the origin of the sympatlletic nerve activities [1]. Recently, it has been suggested that the sympathoexcitatory pathway from the VLDA to the VLPA exists to control cerebral circulation, and that the VLDA controls cerebral vessels via the VLPA and the cervical sympatlletic nerves [4]. The changes in cerebral circulation elicited by SNP may be mediated via the VLDA, VLPA and cervical sympathetic nerves.…”