Response of cerebral neocapillaries to acetylcholine: an intravital microscopic observation

Abstract

The purpose of this study was to examine the response of cerebral neocapillaries to acetylcholine (ACh) in mice. Wild type male mice were used. After anesthesia, a small area of the bone over the parietal cortex was removed to expose the cerebral cortex. The gel–nylon mesh sandwich system was placed over the exposed area. The growth factors bFGF and PDGF were used at a concentration of 6 ng/ml. After the surgical area was covered with a polyurethane biomembrane, the skin was closed with sutures. After 28 days of incubation, the neocapillaries were topically suffused with ACh and the responses of the vascular diameter and red blood cell (RBC) velocity were evaluated using intravital video microscopy. A control group was included to examine the responses of the pial vessels to ACh. A significant increase in vascular diameter and RBC velocity was observed in the control group, while the neocapillaries failed to show anything significant in the bFGF group. However, a significant increase in RBC velocity from the baseline value was observed in the PDGF group. It is suggested that the neocapillaries might have matured in the PDGF group with the formation of pericytes/smooth muscle cell function (SMC), leading to relaxation via the cGMP pathway.