CEREBRAL VASOCONSTRICTIVE RESPONSE PRODUCED BY CHEMICAL-STIMULATION OF THE CAUDAL VENTROLATERAL MEDULLARY DEPRESSOR AREA IS MEDIATED VIA THE ROSTRAL VENTROLATERAL MEDULLARY PRESSER AREA AND THE CERVICAL SYMPATHETIC-NERVES

It was investigated that the cerebral blood flow (CBF) decrease respon se elicited by chemical stimulation of the caudal ventrolateral medull ary depressor area (VLDA) is mediated via the rostral ventrolateral me dullary presser area (VLPA) and the cervical sympathetic nerve. The CB F was determined by radiolabeled microsphere technique in urethane (1. 1-1.5 g kg(-1), i.p.) anesthetized Wistar rats. (i) Microinjection of L-glutamate (1.7 nmol) into the VLDA produced a significant (P < 0.01) decrease in CBF from 64 +/- 9 (mean +/- SEM) to 48 +/- 9 ml min(-1) ( 100 g)(-1) and a significant (P < 0.01) increase in cerebrovascular re sistance (CVR) from 1.7 +/- 0.2 to 2.4 +/- 0.4 mmHg per [ml min(-1) (1 00 g)(-1)] in the cerebral cortex ipsilateral to the stimulated VLDA s ide (n = 9). (ii) After cervical sympathectomy, L-glutamate was unilat erally microinjected into the VLDA. The CBF and CVR did not change sig nificantly (n = 10). (iii) After depression of the VLPA neurons with m uscimol (GABA agonist), L-glutamate was unilaterally microinjected int o the VLDA. The CBF and CVR did not change significantly (n = 14). The se results suggest that the pathway from the VLDA to control cerebral vessels may be mediated via the VLPA and the cervical sympathetic nerv es.