SUPRAMEDULLARY MODULATION OF SYMPATHETIC VASOMOTOR FUNCTION

1, Supramedullary structures including the ventral medial prefrontal c ortex (MPFC) and the midbrain cuneiform nucleus (CnF) project directly and indirectly to premotor sympathoexcitatory neurons of the rostral ventrolateral medulla (RVLM) that are critically involved in the gener ation of sympathetic vasomotor tone, 2, Electrophysiological studies h ave demonstrated that activation of depressor sites within the MPFC is associated with splanchnic sympathetic vasomotor inhibition and inhib ition of the activity of RVLM sympathoexcitatory neurons, 3, Antidromi c mapping and anatomical studies support the notion that a relay in th e nucleus tractus solitarius is involved in the cardiovascular respons e to MPFC stimulation, 4. The midbrain CnF, which lies adjacent to the midbrain periaqueductal grey, is a sympathoexcitatory region of the m idbrain reticular formation, Sympathoexcitatory responses evoked from the CnF are associated with short-latency excitation of RVLM neurons, 5, Cuneiform nucleus stimulation induces the expression of mRNA for th e immediate early genes c-fos and NGFI-A in midbrain, pontine and hypo thalamic structures, 6, The MPFC and CnF are supramedullary structures with opposing modulatory influences on sympathetic vasomotor drive, w hose roles in cardiovascular control mechanisms warrant further invest igation.