NOVEL METHODOLOGY FOR CALCIUM MEASUREMENTS IN CONSCIOUS MICE: AN APPLICATION TO ARTERIOLAR VASOMOTION

Abstract

We developed a method employing two-photon microscopy and genetically engineered ‘Ca2+- biosensor’ mice to measure Ca2+ signaling in arteries of conscious, head-fixed mice. Arterial blood pressure was measured simultaneously via implanted telemetric pressure transducers. These methods allowed, for the first time, the study of control of arterial [Ca2+], diameter, and blood pressure by sympathetic nerve activity (SNA) as it normally exists in conscious animals. We tested the hypothesis that arterial vasomotion, observed more frequently in conscious animals than in anesthetized animals, was generated by SNA that caused synchronous Ca2+-oscillations in smooth muscle. We also measured the changes in arterial [Ca2+] that occur during the time course of experimental hypertension. Pharmacological block of SNA and isoflurane anesthesia eliminated and attenuated, respectively, vasomotion and reduced arterial [Ca2+] (320 ± 48 nM to 241 ± 20 nM and 302 ± 48 nM). This method allows for longitudinal studies of important chronic vascular pathologies.