[Dynamics of local vascular reactions during increased brain activity]

The dynamics of dilatant responses of the pial microvascular system was investigated under conditions of increased cortical activity due to direct application of suprathreshold concentrations of strychnine in experiments on adult rabbits using direct cinemicrography. The diameter of the following interconnected segments of pial arteries was measured in every frame of the film: comparatively large pial arteries (LPA), sphincters at off-shoots of smaller branches (SO), minor pial arteries (MPA), and precortical arteries (PCA). The experiments showed that the order of values of dilatant responses was: PCA greater than SO greater than MPA greater than LPA. The order of the latencies was: PCA less than SO less than MPA less than LPA. The revealed behaviour of the pial microvascular system maintains the adequacy of local blood supply as well as the elimination of the "steal phenomenon" in the neighbouring cortical areas.