AUTORADIOGRAPHIC STUDY OF THE CEREBROVASCULAR EFFECTS OF STIMULATION OF THE SUBSTANTIA INNOMINATA - CONVENIENT STIMULATION PARADIGM

The aim of this study was to determine the distribution within the who le brain of the vascular effects of stimulation of the substantia inno minata. This basal forebrain nucleus is the major cholinergic input in the neocortex in the rodent. The local cerebral blood flow was measur ed by the autoradiographic [C-14]iodoantipyrine technique in a group o f control and a group of stimulated unanesthetized rats. The substanti a innominata was electrically stimulated through a chronically implant ed electrode. The stimulation induced blood flow increases exceeding 2 00% in the hemisphere ipsilateral to the stimulation and 100% in the c ontralateral hemisphere compared to the control group. The ipsilateral vasodilations were observed not only in the cortical areas but also i n some subcortical structures. Comparison with previous data suggests that part of the effects is due to cholinergic neurons of the substant ia innominata and part to non-cholinergic neurons and indirect effects . However, only two out of eight stimulated rats displayed this respon se. The low reproducibility of the results is discussed, considering t he stimulation paradigm which has been developed for future measuremen ts of the cerebral glucose utilization which requires a long duration stimulation period.