Enhanced myogenic depolarization in hypertensive cerebral arterial muscle

We have previously demonstrated pressure-dependent membrane depolarization and action potential generation in cat cerebral arteries. It was the purpose of this study to examine and compare the membrane electrical responses to increasing transmural pressure in spontaneously hypertensive rats with those of their normotensive Wistar-Kyoto controls. It was found that at transmural pressures from 40-160 mm Hg, spontaneously hypertensive rat cerebral arterial muscle depolarized more than normotensive counterparts. Pressure-induced action potentials could be recorded from arterial segments from both animal strains; however, the amplitude and upstroke velocity was significantly greater in spontaneously hypertensive rat cerebral arterial muscle. These data suggest that there are altered ionic permeabilities in spontaneously hypertensive rat cerebral arterial muscle which result in enhanced response to increasing transmural pressure. The implications of these findings are discussed.