{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,24]],"date-time":"2026-03-24T03:43:58Z","timestamp":1774323838625,"version":"3.50.1"},"reference-count":59,"publisher":"American Physiological Society","issue":"5","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["American Journal of Physiology-Heart and Circulatory Physiology"],"published-print":{"date-parts":[[2004,11]]},"abstract":"<jats:p>Mechanisms that underlie autoregulation in the newborn vasculature are unclear. Here we tested the hypothesis that in newborn porcine cerebral arteries intravascular pressure elevates wall tension, leading to an increase in intracellular calcium concentration ([Ca<jats:sup>2+<\/jats:sup>]<jats:sub>i<\/jats:sub>) and a constriction that is opposed by pressure-induced K<jats:sup>+<\/jats:sup>channel activation. Incremental step (20 mmHg) elevations in intravascular pressure between 10 and 90 mmHg induced an immediate transient elevation in arterial wall [Ca<jats:sup>2+<\/jats:sup>]<jats:sub>i<\/jats:sub>and a short-lived constriction that was followed by a smaller steady-state [Ca<jats:sup>2+<\/jats:sup>]<jats:sub>i<\/jats:sub>elevation and sustained constriction. Pressures between 10 and 90 mmHg increased steady-state arterial wall [Ca<jats:sup>2+<\/jats:sup>]<jats:sub>i<\/jats:sub>between \u223c142 and 299 nM and myogenic (defined as passive-active) tension between 25 and 437 dyn\/cm. The relationship between pressure and myogenic tension was strongly Ca<jats:sup>2+<\/jats:sup>dependent until forced dilation. At low pressure, 60 mM K<jats:sup>+<\/jats:sup>induced a steady-state elevation in arterial wall [Ca<jats:sup>2+<\/jats:sup>]<jats:sub>i<\/jats:sub>and a constriction. Nimodipine, a voltage-dependent Ca<jats:sup>2+<\/jats:sup>channel blocker, and removal of extracellular Ca<jats:sup>2+<\/jats:sup>similarly dilated arteries at low or high pressures. 4-Aminopyridine, a voltage-dependent K<jats:sup>+<\/jats:sup>(K<jats:sub>v<\/jats:sub>) channel blocker, induced significantly larger constrictions at high pressure, when compared with those at low pressure. Although selective Ca<jats:sup>2+<\/jats:sup>-activated K<jats:sup>+<\/jats:sup>(K<jats:sub>Ca<\/jats:sub>) channel blockers and intracellular Ca<jats:sup>2+<\/jats:sup>release inhibitors induced only small constrictions at low and high pressures, a low concentration of caffeine (1 \u03bcM), a ryanodine-sensitive Ca<jats:sup>2+<\/jats:sup>release (RyR) channel activator, increased K<jats:sub>Ca<\/jats:sub>channel activity and induced dilation. These data suggest that in newborn cerebral arteries, intravascular pressure elevates wall tension, leading to voltage-dependent Ca<jats:sup>2+<\/jats:sup>channel activation, an increase in wall [Ca<jats:sup>2+<\/jats:sup>]<jats:sub>i<\/jats:sub>and Ca<jats:sup>2+<\/jats:sup>-dependent constriction. In addition, pressure strongly activates K<jats:sub>v<\/jats:sub>channels that opposes constriction but only weakly activates K<jats:sub>Ca<\/jats:sub>channels.<\/jats:p>","DOI":"10.1152\/ajpheart.00660.2004","type":"journal-article","created":{"date-parts":[[2004,7,30]],"date-time":"2004-07-30T00:15:05Z","timestamp":1091146505000},"page":"H2061-H2069","source":"Crossref","is-referenced-by-count":23,"title":["Ionic mechanisms mediating the myogenic response in newborn porcine cerebral arteries"],"prefix":"10.1152","volume":"287","author":[{"given":"Abu","family":"Ahmed","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Christopher M.","family":"Waters","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Charles W.","family":"Leffler","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jonathan 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