Journal of Pharmacological Sciences (Jan 2009)
Comparative Study of Calcium Ion Dynamics and Contractile Response in Rat Middle Cerebral and Basilar Arteries
Abstract
The objective of this study was to compare intracellular calcium concentration ([Ca2+]i) and contractile responses in isolated rat middle cerebral artery (MCA) with those in basilar artery (BA) employing real-time confocal laser microscopy. KCl elicited transient [Ca2+]i elevation and sustained contraction in both arteries; moreover, nearly equal responses were evident in both arteries. Application of 5-hydroxytryptamine (5-HT), vasopressin (VP), and α,β-methylene adenosine 5’-triphosphate (α,β-me ATP) also induced elevation of [Ca2+]i and contraction in both arteries. The maximum response of 5-HT and VP necessary to increase [Ca2+]i and to constrict the MCA was less in comparison to the BA; however, a linear relationship emerged between the maximum response of [Ca2+]i and that of contraction. Additionally, the slope of the correlation regression line of MCA was nearly identical to that of BA. On the other hand, cyclopiazonic acid (CPA)-induced Ca2+ release from store sites following contraction of MCA was distinct from that of BA. In MCA, velocity of [Ca2+]i elevation in smooth muscle cells and Ca2+-wave propagation along smooth muscle cells induced by 5-HT were slower than those in BA. These observations revealed that different regions of arteries along the same cerebral tissue may display distinct [Ca2+]i response; moreover, this difference may be one reason for the distinct contractile response. Keywords:: confocal microscopy, intracellular calcium, basilar artery, middle cerebral artery