Abstract #0186

Negative Cerebral Blood Flow and BOLD Responses to Somatosensory Stimulation in Spontaneously Hypertensive Rats

Renata Ferranti Leoni^1,2, Draulio Barros de Araujo², Afonso Costa Silva³

¹Cerebral Microcirculation Unit , National Institute of Neurological Diseases and Stroke - NINDS/NIH, Bethesda, MD, United States; ²Department of Physics and Mathematics, University of Sao Paulo, Ribeirao Preto, Sao Paulo, Brazil; ³Cerebral Microcirculation Unit, National Institute of Neurological Diseases and Stroke - NINDS/NIH, Bethesda, MD, United States

The presence of sustained negative fMRI response to focal brain stimulation can be explained either by decreased local neuronal activity (neuronal surround inhibition) or by decreased cerebrovascular reserve (vascular steal effect). Here we measured the CBF and BOLD responses to somatosensory stimulation in spontaneously hypertensive rats (SHR) and normotensive controls, to test the origin of negative fMRI responses. 20/30 SHR, but only 3/25 normotensive rats, presented robust negative CBF and BOLD responses. We conclude that the negative fMRI responses were largely related to a vascular steal effect and not due to neuronal surround inhibition.