Research ReportRegulation of cerebral blood flow in the hippocampus by neuronal activation through the perforant path: Relationship between hippocampal blood flow and neuronal plasticity

Although changes in regional cerebral blood flow (rCBF) have been used as an index of neuronal activity, the effects of long-term potentiation (LTP) in the hippocampus, widely assumed to be an electrophysiological basis of learning and memory, on the changes in rCBF by neuronal activity remain unclear. Hence, to elucidate whether the effects of LTP in the hippocampus reflect in the correlation between neuronal activity and co-occurring changes in rCBF, we investigated the effects of LTP on the responses of hippocampal blood flow (HBF) to the electrical stimulation of the perforant path in vivo. We continuously measured HBF using Laser-Doppler flowmetry, and systemic blood pressure and heart rate were measured from the femoral artery during electrical stimulations in halothane-anesthetized rats. The results showed that the reactivity of HBF to neuronal activation was potentiated by a tetanic stimulation that induces LTP, although the tetanic stimulation did not affect baseline of HBF values. These results suggest that the presence of the plasticity between neuronal activity and the rCBF in the perforant path-dentate pathway, and the neuronal plasticity can be reflected in the transient changes in rCBF when the brain region is activated but not in the steady state.

► HBF was increased by electrical stimulation of the perforant path in vivo. ► Increases of HBF required a train of electrical stimulation. ► A maximum increase of HBF was induced by 5-10 Hz stimulation. ► LTP-like phenomena occurred in HBF response by tetanic stimulation. ► Degree of afferent input and synaptic transmission efficiency regulate HBF.