CAUDAL VENTROLATERAL MEDULLARY DEPRESSOR AREA CONTROLS CEREBRAL-CIRCULATION VIA ROSTRAL VENTROLATERAL MEDULLARY PRESSER AREA

The cerebral bleed flow (CBF) ass determined by radiolabeled microsphe re technique in urethane (1.1-1.5 g kg i.p.) anesthetized Wistar rats. Microinjection of L-glutamate (1.7 nmol) into the ventrolateral medul lary 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 (CV R) 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 i n other structures such as brain stem and cerebellum (n=9). Cervical s ympathectomy blocked the decrease in CBF and increase in CVR elicited by chemical stimulation of the VLDA (n=10). Depression of the ventrola teral medullary presser area (VLPA) neurons induced by microinjection of muscimol into the VLPA blocked the CBF decrease and CVR increase fo llowing chemical stimulation of the VLDA (n=11). Microinjection of the vehicle solution into the VLDA had no effects on systemic and cerebra l circulation (n=7). These results suggest that a vasoconstrictor path way to control cerebral vessels involves an excitatory projection from the VLDA to the VLPA and the changes in cerebral circulation are medi ated by the cervical sympathetic nerves.