Neurons of nucleus of the solitary tract synchronize the EEG and elevate cerebral blood flow via a novel medullary area

In anesthetized spinalized rat, electrical stimulation of the nucleus tract us solitarius (NTS) synchronizes the EEG by increasing the power of 4-6-Hz waves (>100%; P<0.01), and elevates cerebral blood flow (rCBF) by 18+/-5% ( P<0.05). The coordinated response appears within seconds, is global, revers ible, graded, evoked from the commissural sub-nucleus, and replicated by L- glutamate. The responses are markedly reduced by bilateral lesions or musci mol microinjections restricted to a region of ventral medullary reticular f ormation, the medullary cerebral vasodilator area (MCVA), a region from whi ch stimulation elicits identical responses and mediates the comparable resp onses to hypoxic/ischemic excitation of sympathoexcitatory neurons of rostr al ventrolateral medulla (RVLM). We conclude that: (a) excitation of intrin sic neurons of commissural NTS synchronizes the EEG and coordinately elevat es rCBF; (b) the responses are mediated by excitation of neurons in MCVA; ( c) the MCVA may be a common final pathway mediating cerebrovascular and EEG responses from multiple areas of CNS; and (d) the NTS-MCVA pathway may be a part of the anatomical substrate for behaviors, including slow-wave sleep and seizure suppression evoked by stimulation of visceral afferents termin ating in NTS. (C) 2001 Elsevier Science B.V. All rights reserved.