Spontaneous and neurogenic constriction of microvasculature in the rat hippocampal slice.

The hippocampal slice is characterized by laminar organization and defined synaptic circuitry and provides an in vitro model system for the study of neuronal membrane properties, the action of putative neurotransmitters, and synaptic plasticity. Because the hippocampus is densely vascularized and hippocampal microvessels respond to a variety of stimuli that also affect the activity of neurons in the slice, the preparation is also especially well suited to investigating the physiologic relationship between neurons and intraparenchymal blood vessels. Here we address the issue of potential neurogenic control of cerebral microvasculature using electrical stimuli and specific neurotoxins. A small proportion of slice microvessels displayed spontaneous rhythmic activity that was independent of any exogenous stimulus. The majority of slices examined contained microvessels that responded to a train of electrical impulses delivered to discrete neural pathways. Under particular stimulus conditions, the vascular response could be completely blocked by 1 microM tetrodotoxin. The results are taken to support the existence of a neurogenic influence on penetrating arterioles.