[Features of physiologic mechanisms regulating microcirculation in the cerebral cortex of birds and mammals].

The responses of pial arteries to increased activity of the cerebral cortex as well as their innervation at various stages of phylogenic development, were studied with the aid of serial photomicrography with subsequent frame-to-frame analysis in adult rabbits and hens. Following the application of 0.5% isotonic strychnine solution to brain surface, the dilatation of all the segments of the pial artery ramifications was considerably more obvious in rabbits than in hens. The latencies of the vascular responses differed in a similar way. Histochemical studies revealed a considerably richer adren- and cholinergic innervation in rabbit pial arteries as compared with those of hens. The vascular responses and the neurogenic control of the pial arterial bed seem to become steadily refined, together with its anatomy, in the course of evolutionary development.