Presence of Afferent Nerve Fibers in Meningeal Blood Vessel Walls.

Abstract

The presence of vasomotor nerves in the cerebral blood vessels seems well established as a result of the work of Nothnagel, 1 Wiggers, 2 Brown, 3 Anrep and Starling, 4 and Forbes and Wolff. 5 Anatomical studies, particularly by Alexander, 6 Gulland, 7 Huber, 8 Hunter, 9 Traum, 10 and Stohr, 11 have suggested the presence of sensory nerve-endings in the pial blood vessel walls. We have been unable to find any physiological work on these supposed afferent nerveendings.

In connection with a series of dogs, in which dilatation of the pial blood vessels was studied, as previously reported, 12 we made a number of observations on reflex stimulation of respiration and blood pressure following electrical stimuli applied to the meningeal vessels and directly to the dura. As controls, we used the same strength of faradic current to obtain reflex effects from the stimulation of the femoral blood vessels. We varied the procedure considerably in order to avoid unfair conclusions with regard to the relative sensitivity of these various areas. In these experiments the depth of anesthesia must be maintained the same throughout. Furthermore, we noted that pressure variations in the application of the electrodes would cause variations in the reactions, and that, under some circumstances, cauterization might occur. Great care was necessary to avoid these complications. We considered as significant, changes beyond 8 per minute in respiratory or heart rate, and greater than 6 mm. of mercury in the mean blood pressure.

We found that electrical stimulation applied to the blood vessels of the dura mater or pia mater caused a greater effect than the same strength of current applied directly to the meningeal surfaces between blood-vessels. Surgeons operating on the brain under local anesthesia, but without the meninges anesthetized, have noted in cutting the meninges that pain is felt chiefly when the meningeal vessels are cut, or trarnatized. 13