CARDIOVASCULAR-RESPONSES TO GLOBAL CEREBRAL-ISCHEMIA - ROLE OF EXCITATORY AMINO-ACIDS IN THE VENTROLATERAL MEDULLARY PRESSOR AREA

The object of this study was to investigate the role of the ventrolate ral medullary pressor area in mediating the cardiovascular responses t o experimentally induced global cerebral ischemia, and to test if exci tatory amino acids or acetylcholine are the transmitters released in t his brain region during these responses. The cerebral ischemic respons e was elicited in pentobarbital-anesthetized, artificially ventilated male Wistar rats by bilateral ligation of vertebral arteries followed by temporary clamping of the common carotid arteries. The pressor area was identified by microinjections of L-glutamate. Inhibition of neuro ns in this area by microinjections of muscimol, a gamma-aminobutyric a cid receptor agonist, abolished the ischemic response, which demonstra ted that this area is important in mediating these responses. Microinj ections of a broad-spectrum excitatory amino acid receptor blocker (ky nurenate), of specific antagonists for N-methyl-D-aspartic acid (NMDA) and non-NMDA receptors (injected alone or in combination), and of atr opine failed to block the ischemic responses. These results indicate t hat: 1) the ventrolateral medullary pressor area mediates pressor resp onses to cerebral ischemia, and 2) excitatory amino acids or acetylcho line in this area do not mediate the cardiovascular responses to cereb ral ischemia.